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lintr (development version)

Deprecations & breaking changes

  • Various things marked deprecated since {lintr} 3.0.0 have been fully deprecated. They will be completely removed in the subsequent release.
    • source_file= argument to ids_with_token() and with_id().
    • Passing linters by name or as non-"linter"-classed functions.
    • linter= argument of Lint().
    • Linters closed_curly_linter(), open_curly_linter(), paren_brace_linter(), and semicolon_terminator_linter()..
    • with_defaults().
    • Linters closed_curly_linter(), open_curly_linter(), paren_brace_linter(), and semicolon_terminator_linter().
    • Helper with_defaults().
  • all_linters() has signature all_linters(..., packages) rather than all_linters(packages, ...) (#2332, @MichaelChirico). This forces packages= to be supplied by name and will break users who rely on supplying packages= positionally, of which we found none searching GitHub.
  • Adjusted various lint messages for consistency in readability (#1330, @MichaelChirico). In general, we favor lint messages to be phrased like "Action, reason" to but the "what" piece of the message front-and-center. This may be a breaking change for code that tests the specific phrasing of lints.
  • extraction_operator_linter() is deprecated. Although switching from $ to [[ has some robustness benefits for package code, it can lead to non-idiomatic code in many contexts (e.g. R6 classes, Shiny applications, etc.) (#2409, @IndrajeetPatil). To enable the detection of the $ operator for extraction through partial matching, use options(warnPartialMatchDollar = TRUE).
  • unnecessary_nested_if_linter() is deprecated and subsumed into the new/more general unnecessary_nesting_linter().
  • Drop support for posting GitHub comments from inside GitHub comment bot, Travis, Wercker, and Jenkins CI tools (spurred by #2148, @MichaelChirico). We rely on GitHub Actions for linting in CI, and don't see any active users relying on these alternatives. We welcome and encourage community contributions to get support for different CI system going again.
  • cyclocomp_linter() is no longer part of the default linters (#2555, @IndrajeetPatil) because the tidyverse style guide doesn't contain any guidelines on meeting certain complexity requirements. Note that users with cyclocomp_linter() in their configs may now need to install {cyclocomp} intentionally, in particular in CI/CD pipelines.
  • scalar_in_linter is now configurable to allow other %in% like operators to be linted. The data.table operator %chin% is no longer linted by default; use in_operators = "%chin%" to continue linting it. (@F-Noelle)

Bug fixes

  • object_name_linter() no longer errors when user-supplied regexes= have capture groups (#2188, @MichaelChirico).
  • .lintr config validation correctly accepts regular expressions which only compile under perl = TRUE (#2375, @MichaelChirico). These have always been valid (since rex::re_matches(), which powers the lint exclusion logic, also uses this setting), but the new up-front validation in v3.1.1 incorrectly used perl = FALSE.
  • .lintr configs set by option lintr.linter_file or environment variable R_LINTR_LINTER_FILE can point to subdirectories (#2512, @MichaelChirico).
  • indentation_linter() returns ranges[1L]==1L when the offending line has 0 spaces (#2550, @MichaelChirico).
  • literal_coercion_linter() doesn't surface a warning about NAs during coercion for code like as.integer("a") (#2566, @MichaelChirico).

Changes to default linters

  • New default linter return_linter() for the style guide rule that terminal returns should be left implicit (#1100, #2343, #2354, and #2356, @MEO265 and @MichaelChirico).

New and improved features

  • More helpful errors for invalid configs (#2253, @MichaelChirico).
  • library_call_linter() is extended
    • to encourage all packages to be attached with library(symbol), not library("symbol", character.only = TRUE) or "vectorized" approaches looping over package names (part of #884, @MichaelChirico).
    • to discourage many consecutive calls to suppressMessages() or suppressPackageStartupMessages() (part of #884, @MichaelChirico).
  • return_linter() also has arguments for fine-tuning which functions get linted:
    • return_style ("implicit" by default) which checks that all functions confirm to the specified return style of "implicit" or "explicit" (#2271 and part of #884, @MichaelChirico, @AshesITR and @MEO265).
    • allow_implicit_else (default TRUE) which, when FALSE, checks that all terminal if statements are paired with a corresponding else statement (part of #884, @MichaelChirico).
    • return_functions to customize which functions are equivalent to return() as "exit" clauses, e.g. rlang::abort() can be considered in addition to the default functions like stop() and q() from base (#2271 and part of #884, @MichaelChirico and @MEO265).
    • except to customize which functions are ignored entirely (i.e., whether they have a return of the specified style is not checked; #2271 and part of #884, @MichaelChirico and @MEO265). Namespace hooks like .onAttach() and .onLoad() are always ignored.
    • except_regex, the same purpose as except=, but filters functions by pattern. This is motivated by {RUnit}, where test suites are based on unit test functions matched by pattern, e.g. ^Test, and where explicit return may be awkward (#2335, @MichaelChirico).
  • unnecessary_lambda_linter is extended to encourage vectorized comparisons where possible, e.g. sapply(x, sum) > 0 instead of sapply(x, function(x) sum(x) > 0) (part of #884, @MichaelChirico). Toggle this behavior with argument allow_comparison.
  • backport_linter() is slightly faster by moving expensive computations outside the linting function (#2339, #2348, @AshesITR and @MichaelChirico).
  • Linter() has a new argument linter_level (default NA). This is used by lint() to more efficiently check for expression levels than the idiom if (!is_lint_level(...)) { return(list()) } (#2351, @AshesITR).
  • string_boundary_linter() recognizes regular expression calls like grepl("^abc$", x) that can be replaced by using == instead (#1613, @MichaelChirico).
  • unreachable_code_linter() has an argument allow_comment_regex for customizing which "terminal" comments to exclude (#2327, @MichaelChirico). # nolint end comments are always excluded, as are {covr} exclusions (e.g. # nocov end) by default.
  • format() and print() methods for lint and lints classes get a new option width to control the printing width of lint messages (#1884, @MichaelChirico). The default is controlled by a new option lintr.format_width; if unset, no wrapping occurs (matching earlier behavior).
  • implicit_assignment_linter() gets a custom message for the case of using ( to induce printing like (x <- foo()); use an explicit call to print() for clarity (#2257, @MichaelChirico).
  • New function node caching for big efficiency gains to most linters (e.g. overall lint_package() improvement of 14-27% and core linting improvement up to 30%; #2357, @AshesITR). Most linters are written around function usage, and XPath performance searching for many functions is poor. The new xml_find_function_calls() entry in the get_source_expressions() output caches all function call nodes instead. See the vignette on creating linters for more details on how to use it.
  • todo_comment_linter() has a new argument except_regex for setting valid TODO comments, e.g. for forcing TODO comments to be linked to GitHub issues like TODO(#154) (#2047, @MichaelChirico).
  • vector_logic_linter() is extended to recognize incorrect usage of scalar operators && and || inside subsetting expressions like dplyr::filter(x, A && B) (#2166, @MichaelChirico).
  • any_is_na_linter() is extended to catch the unusual usage NA %in% x (#2113, @MichaelChirico).
  • make_linter_from_xpath() errors up front when lint_message is missing (instead of delaying this error until the linter is used, #2541, @MichaelChirico).
  • paste_linter() is extended to recommend using paste() instead of paste0() for simply aggregating a character vector with collapse=, i.e., when sep= is irrelevant (#1108, @MichaelChirico).

New linters

  • condition_call_linter() for ensuring consistent use of call. in warning() and stop(). The default call. = FALSE follows the tidyverse guidance of not displaying the call (#2226, @Bisaloo)
  • sample_int_linter() for encouraging sample.int(n, ...) over equivalents like sample(1:n, ...) (part of #884, @MichaelChirico).
  • stopifnot_all_linter() discourages tests with all() like stopifnot(all(x > 0)); stopifnot() runs all() itself, and uses a better error message (part of #884, @MichaelChirico).
  • comparison_negation_linter() for discouraging negated comparisons when a direct negation is preferable, e.g. !(x == y) could be x != y (part of #884, @MichaelChirico).
  • nzchar_linter() for encouraging nzchar() to test for empty strings, e.g. nchar(x) > 0 can be nzchar(x) (part of #884, @MichaelChirico).
  • terminal_close_linter() for discouraging using close() to end functions (part of #884, @MichaelChirico). Such usages are not robust to errors, where close() will not be run as intended. Put close() in an on.exit() hook, or use {withr} to manage connections with proper cleanup.
  • rep_len_linter() for encouraging use of rep_len() directly instead of rep(x, length.out = n) (part of #884, @MichaelChirico).
  • which_grepl_linter() for discouraging which(grepl(ptn, x)) in favor of directly using grep(ptn, x) (part of #884, @MichaelChirico).
  • list_comparison_linter() for discouraging comparisons on the output of lapply(), e.g. lapply(x, sum) > 10 (part of #884, @MichaelChirico).
  • print_linter() for discouraging usage of print() on string literals like print("Reached here") or print(paste("Found", nrow(DF), "rows.")) (#1894, @MichaelChirico).
  • unnecessary_nesting_linter() for discouraging overly-nested code where an early return or eliminated sub-expression (inside '{') is preferable (#2317, #2334 and part of #884, @MichaelChirico).
  • consecutive_mutate_linter() for encouraging consecutive calls to dplyr::mutate() to be combined (part of #884, @MichaelChirico).
  • if_switch_linter() for encouraging switch() over repeated if/else tests (#2322 and part of #884, @MichaelChirico).
  • nested_pipe_linter() for discouraging pipes within pipes, e.g. df1 %>% inner_join(df2 %>% select(a, b)) (part of #884, @MichaelChirico).
  • nrow_subset_linter() for discouraging usage like nrow(subset(x, conditions)) in favor of something like with(x, sum(conditions)) which doesn't require a full subset of x (#2313, #2314 and part of #884, @MichaelChirico).
  • pipe_return_linter() for discouraging usage of return() inside a {magrittr} pipeline (part of #884, @MichaelChirico).
  • one_call_pipe_linter() for discouraging one-step pipelines like x |> as.character() (#2330 and part of #884, @MichaelChirico).
  • object_overwrite_linter() for discouraging re-use of upstream package exports as local variables (#2344, #2346 and part of #884, @MichaelChirico and @AshesITR).

Lint accuracy fixes: removing false positives

  • object_name_linter() and object_length_linter() ignore {rlang} name injection like x |> mutate("{new_name}" := foo(col)) (#1926, @MichaelChirico). No checking is applied in such cases. {data.table} in-place assignments like DT[, "sPoNGeBob" := "friend"] are still eligible for lints.

lintr 3.1.2

New and improved features

Lint accuracy fixes: removing false positives

  • unreachable_code_linter() ignores reachable code in inline functions like function(x) if (x > 2) stop() else x (#2259, @MEO265).
  • unnecessary_lambda_linter()
    • ignores extractions with explicit returns like lapply(l, function(x) foo(x)$bar) (#2258, @MichaelChirico).
    • ignores calls on the RHS of operators like lapply(l, function(x) "a" %in% names(x)) (#2310, @MichaelChirico).
  • vector_logic_linter() recognizes some cases where bitwise &/| are used correctly (#1453, @MichaelChirico).
  • expect_comparison_linter() ignores faulty usage like expect_true(x, y > z) (#2083, @MichaelChirico). Note that y > z is being passed to the info= argument, so this is likely a mistake.
  • consecutive_assertion_linter() ignores cases where a second assertion follows an intervening assignment with = (#2444, @MichaelChirico).

Lint accuracy fixes: removing false negatives

  • missing_argument_linter() catches all missing arguments in calls with several, e.g. foo(,,) gives 3 lints instead of 2 (#2399, @MichaelChirico).
  • duplicate_argument_linter() no longer misses cases with duplicate arguments where a comment comes between the argument name and = (#2402, @MichaelChirico).

Notes

  • Fixed a test assuming a specific parser error message that recently changed in r-devel (#2527, @IndrajeetPatil).
  • @MichaelChirico has taken over CRAN maintainer duties for the package. Many thanks to @jimhester for more than 10 years and 15 releases wearing that hat!!

lintr 3.1.1

Breaking changes

  • infix_spaces_linter() distinguishes <-, :=, <<- and ->, ->>, i.e. infix_spaces_linter(exclude_operators = "->") will no longer exclude ->> (#2115, @MichaelChirico). This change is breaking for users relying on manually-supplied exclude_operators containing "<-" to also exclude := and <<-. The fix is to manually supply ":=" and "<<-" as well. We don't expect this change to affect many users, the fix is simple, and the new behavior is much more transparent, so we are including this breakage in a minor release.
  • Removed find_line() and find_column() entries from get_source_expressions() expression-level objects. These have been marked deprecated since version 3.0.0. No users were found on GitHub.
  • There is experimental support for writing config in plain R scripts (as opposed to DCF files; #1210, @MichaelChirico). The script is run in a new environment and variables matching settings (?default_settings) are copied over. In particular, this removes the need to write R code in a DCF-friendly way, and allows normal R syntax highlighting in the saved file. We may eventually deprecate the DCF approach in favor of this one; user feedback is welcome on strong preferences for either approach, or for a different approach like YAML. Generally you should be able to convert your existing .lintr file to an equivalent R config by replacing the : key-value separators with assignments (<-). By default, such a config is searched for in a file named .lintr.R. This is a mildly breaking change if you happened to be keeping a file .lintr.R around since that file is given precedence over .lintr.
    • We also validate config files up-front make it clearer when invalid configs are present (#2195, @MichaelChirico). There is a warning for "invalid" settings, i.e., settings not part of ?default_settings. We think this is more likely to affect users declaring settings in R, since any variable defined in the config that's not a setting must be removed to make it clearer which variables are settings vs. ancillary.

Bug fixes

  • sprintf_linter() doesn't error in cases where whitespace in ... arguments is significant, e.g. sprintf("%s", if (A) "" else y), which won't parse if whitespace is removed (#2131, @MichaelChirico).

Changes to default linters

  • assignment_linter() lints the {magrittr} assignment pipe %<>% (#2008, @MichaelChirico). This can be deactivated by setting the new argument allow_pipe_assign to TRUE.
  • object_usage_linter():
    • assumes glue() is glue::glue() when interpret_glue=TRUE (#2032, @MichaelChirico).
    • finds function usages, including infix usage, inside glue() calls to avoid false positives for "unused objects" (#2029 and #2069, @MichaelChirico).
  • object_name_linter() no longer attempts to lint strings in function calls on the LHS of assignments (#1466, @MichaelChirico).
  • infix_spaces_linter() allows finer control for linting = in different scenarios using parse tags EQ_ASSIGN, EQ_SUB, and EQ_FORMALS (#1977, @MichaelChirico).
  • equals_na_linter() checks for x %in% NA, which is a more convoluted form of is.na(x) (#2088, @MichaelChirico).

New and improved features

  • New exclusion sentinel # nolint next to signify the next line should skip linting (#1791, @MichaelChirico). The usual rules apply for excluding specific linters, e.g. # nolint next: assignment_linter.. The exact string used to match a subsequent-line exclusion is controlled by the exclude_next config entry or R option "lintr.exclude_next".
  • New xp_call_name() helper to facilitate writing custom linters (#2023, @MichaelChirico). This helper converts a matched XPath to the R function to which it corresponds. This is useful for including the "offending" function in the lint's message.
  • New make_linter_from_xpath() to facilitate making simple linters directly from a single XPath (#2064, @MichaelChirico). This is especially helpful for making on-the-fly/exploratory linters, but also extends to any case where the linter can be fully defined from a static lint message and single XPath.
  • Toggle lint progress indicators with argument show_progress to lint_dir() and lint_package() (#972, @MichaelChirico). The default is still to show progress in interactive() sessions. Progress is also now shown with a "proper" progress bar (utils::txtProgressBar()), which in particular solves the issue of progress . spilling well past the width of the screen in large directories.
  • lint(), lint_dir(), and lint_package() fail more gracefully when the user mis-spells an argument name (#2134, @MichaelChirico).
  • Quarto files (.qmd) are included by lint_dir() by default (#2150, @dave-lovell).

New linters

  • library_call_linter() can detect if all library/require calls are not at the top of your script (#2027, #2043, #2163, and #2170, @nicholas-masel and @MichaelChirico).
  • keyword_quote_linter() for finding unnecessary or discouraged quoting of symbols in assignment, function arguments, or extraction (part of #884, @MichaelChirico). Quoting is unnecessary when the target is a valid R name, e.g. c("a" = 1) can be c(a = 1). The same goes to assignment ("a" <- 1) and extraction (x$"a"). Where quoting is necessary, the linter encourages doing so with backticks (e.g. x$`a b` instead of x$"a b").
  • length_levels_linter() for using the specific function nlevels() instead of checking length(levels(x)) (part of #884, @MichaelChirico).
  • scalar_in_linter() for discouraging %in% when the right-hand side is a scalar, e.g. x %in% 1 (part of #884, @MichaelChirico).
  • if_not_else_linter() for encouraging if statements to be structured as if (A) x else y instead of if (!A) y else x (part of #884, @MichaelChirico).
  • repeat_linter() for encouraging repeat for infinite loops instead of while (TRUE) (#2106, @MEO265).
  • length_test_linter() detects the common mistake length(x == 0) which is meant to be length(x) == 0 (#1991, @MichaelChirico).

Extensions to existing linters

  • fixed_regex_linter() gains an option allow_unescaped (default FALSE) to toggle linting regexes not requiring any escapes or character classes (#1689, @MichaelChirico). Thus fixed_regex_linter(allow_unescaped = TRUE) would lint on grepl("[$]", x) but not on grepl("a", x) since the latter does not use any regex special characters.
  • line_length_linter() helpfully includes the line length in the lint message (#2057, @MichaelChirico).
  • conjunct_test_linter() also lints usage like dplyr::filter(x, A & B) in favor of using dplyr::filter(x, A, B) (part of #884; #2110 and #2078, @salim-b and @MichaelChirico). Option allow_filter toggles when this applies. allow_filter = "always" drops such lints entirely, while "not_dplyr" only lints calls explicitly qualified as dplyr::filter(). The default, "never", assumes all unqualified calls to filter() are dplyr::filter().
  • sort_linter() checks for code like x == sort(x) which is better served by using the function is.unsorted() (part of #884, @MichaelChirico).
  • paste_linter() gains detection for file paths that are better constructed with file.path(), e.g. paste0(dir, "/", file) would be better as file.path(dir, file) (part of #884, #2082, @MichaelChirico). What exactly gets linted here can be fine-tuned with the allow_file_path option ("double_slash" by default, with alternatives "never" and "always"). When "always", these rules are ignored. When "double_slash", paths appearing to construct a URL that have consecutive forward slashes (/) are skipped. When "never", even URLs should be constructed with file.path().
  • seq_linter() recommends rev() in the lint message for lints like nrow(x):1 (#1542, @MichaelChirico).
  • function_argument_linter() detects usage of missing() for the linted argument (#1546, @MichaelChirico). The simplest fix for function_argument_linter() lints is typically to set that argument to NULL by default, in which case it's usually preferable to update function logic checking missing() to check is.null() instead.
  • commas_linter() gains an option allow_trailing (default FALSE) to allow trailing commas while indexing. (#2104, @MEO265)
  • unreachable_code_linter()
    • checks for code inside if (FALSE) and other conditional loops with deterministically false conditions (#1428, @ME0265).
    • checks for unreachable code inside if, else, for, while, and repeat blocks, including combinations with break and next statements. (#2105, @ME0265).
  • implicit_assignment_linter() gains an argument allow_lazy (default FALSE) that allows optionally skipping lazy assignments like A && (B <- foo(A)) (#2016, @MichaelChirico).
  • unused_import_linter() gains an argument interpret_glue (default TRUE) paralleling that in object_usage_linter() to toggle whether glue::glue() expressions should be inspected for exported object usage (#2042, @MichaelChirico).
  • default_undesirable_functions is updated to also include Sys.unsetenv() and structure() (#2192 and #2228, @IndrajeetPatil and @MichaelChirico).
  • Linters with logic around the magrittr pipe %>% consistently apply it to the other pipes %!>%, %T>%, %<>% (and possibly %$%) where appropriate (#2008, @MichaelChirico).
    • brace_linter()
    • pipe_call_linter()
    • pipe_continuation_linter()
    • unnecessary_concatenation_linter()
    • unnecessary_placeholder_linter()
  • Linters with logic around function declarations consistently include the R 4.0.0 shorthand \() (#2190, @MichaelChirico).
    • brace_linter()
    • function_left_parentheses_linter()
    • indentation_linter()
    • object_length_linter()
    • object_name_linter()
    • package_hooks_linter()
    • paren_body_linter()
    • unnecessary_lambda_linter()
    • unreachable_code_linter()

Lint accuracy fixes: removing false positives

  • fixed_regex_linter()
    • Is pipe-aware, in particular removing false positives around piping into {stringr} functions like x |> str_replace(fixed("a"), "b") (#1811, @MichaelChirico).
    • Ignores non-string inputs to pattern= as a keyword argument (#2159, @MichaelChirico).
  • Several linters avoiding false positives in $ extractions get the same exceptions for @ extractions, e.g. S4@T will no longer throw a T_and_F_symbol_linter() hit (#2039, @MichaelChirico).
    • T_and_F_symbol_linter()
    • for_loop_index_linter()
    • literal_coercion_linter()
    • object_name_linter()
    • undesirable_function_linter()
    • unreachable_code_linter()
    • yoda_test_linter()
  • sprintf_linter() is pipe-aware, so that x %>% sprintf(fmt = "%s") no longer lints (#1943, @MichaelChirico).
  • condition_message_linter() ignores usages of extracted calls like env$stop(paste(a, b)) (#1455, @MichaelChirico).
  • inner_combine_linter() no longer throws on length-1 calls to c() like c(exp(2)) or c(log(3)) (#2017, @MichaelChirico). Such usage is discouraged by unnecessary_concatenation_linter(), but inner_combine_linter() per se does not apply.
  • sort_linter() only lints on order() of a single vector, excluding e.g. x[order(x, y)] and x[order(y, x)] (#2156, @MichaelChirico).
  • redundant_ifelse_linter() is aware of dplyr::if_else()'s missing= argument, so that if_else(A, TRUE, FALSE, missing = FALSE) doesn't lint, but if_else(A, TRUE, FALSE, NA) does (#1941, @MichaelChirico). Note that dplyr::coalesce() or tidyr::replace_na() may still be preferable.

Lint accuracy fixes: removing false negatives

  • unreachable_code_linter() finds unreachable code even in the presence of a comment or semicolon after return() or stop() (#2127, @MEO265).
  • implicit_assignment_linter()
    • finds assignments in call arguments besides the first one (#2136, @MichaelChirico).
    • finds assignments in parenthetical expressions like if (A && (B <- foo(A))) { } (#2138, @MichaelChirico).
  • unnecessary_lambda_linter() checks for cases using explicit returns, e.g. lapply(x, \(xi) return(sum(xi))) (#1567, @MichaelChirico).
    • thanks to @Bisaloo and @strengejacke for detecting a regression in the original fix (#2231, #2247).

lintr 3.1.0

Deprecations & Breaking Changes

  • .lintr files can now be kept in the directory .github/linters for better compatibility with Super-Linter. Note that this may be a breaking change if you already have a config in .github/linters inside a subdirectory as well as in your R project's root, since the former will now be discovered first where it was ignored before. Please see vignette("lintr") for details on how configs are discovered (#1746, @tonyk7440 and @klmr).
  • single_quotes_linter() is deprecated in favor of the more generalizable quotes_linter() (#1729, @MichaelChirico).
  • unneeded_concatentation_linter() is deprecated in favor of unnecessary_concatenation_linter() for naming consistency (#1707, @IndrajeetPatil).
  • consecutive_stopifnot_linter() is deprecated in favor of the more general (see below) consecutive_assertion_linter() (#1604, @MichaelChirico).
  • no_tab_linter() is deprecated in favor of whitespace_linter() for naming consistency and future generalization (#1954, @MichaelChirico).
  • available_linters() prioritizes tags over exclude_tags in the case of overlap, i.e., tags listed in both arguments are included, not excluded. We don't expect many people to be affected by this, and the old behavior was not made explicit in the documentation, but make note of it here since it required changing a test in lintr's own suite where linters_with_tags() implicitly assumed this behavior.
  • lint(), lint_dir(), and lint_package() no longer accept certain arguments (cache= for lint(), relative_path= for the latter two) positionally. The warning() since 3.0.0 has been upgraded to an error.

Bug fixes

  • linters_with_tags() now includes the previously missing spaces around "and" when listing missing linters advertised by available_linters(). This error message may appear e.g. when you update lintr to a version with new linters but don't restart your R session (#1946, @Bisaloo)

  • fixed_regex_linter() is more robust to errors stemming from unrecognized escapes (#1545, #1845, @IndrajeetPatil).

  • get_source_expressions() can handle Sweave/Rmarkdown documents with reference chunks like <<ref_file>> (#779, @MichaelChirico). Note that these are simply skipped, rather than attempting to retrieve the reference and also lint it.

  • assignment_linter() no longer lints assignments in braces that include comments when allow_trailing = FALSE (#1701, @ashbaldry)

  • object_usage_linter()

    • No longer silently ignores usage warnings that don't contain a quoted name (#1714, @AshesITR)
    • No longer fails on code with comments inside a multi-line call to glue::glue() (#1919, @MichaelChirico)

  • namespace_linter() correctly recognizes backticked operators to be exported from respective namespaces (like rlang::`%||%`) (#1752, @IndrajeetPatil)

  • lint_package() correctly finds a package from within a subdir if the path points to anywhere within the package (#1759, @AshesITR)

  • Improved error behavior in Lint(), lint() and xml_nodes_to_lints() (#1427, #763, @AshesITR)

    • Lint() validates its inputs more thoroughly, preventing errors during print.Lints like "Error in rep.int(character, length) : invalid 'times' value:".
    • lint() no longer tries to create an expression tree with unexpected end of input errors, because they can be broken.
    • xml_nodes_to_lints() warns if it can't find lint locations and uses dummy locations as a fallback.

  • linters_with_defaults() no longer erroneously marks linter factories as linters (#1725, @AshesITR).

  • Row names for available_linters() data frame are now contiguous (#1781, @IndrajeetPatil).

  • object_name_linter() allows all S3 group Generics (see ?base::groupGeneric) and S3 generics defined in a different file in the same package (#1808, #1841, @AshesITR)

  • object_usage_linter() improves identification of the exact source of a lint

    • for undefined variables in expressions with where the variable is used as a symbol in a usual way, for example in a formula or in an extraction with $ (#1914, @MichaelChirico).
    • for general usage warnings without location info (#1986 and #1917, @AshesITR)

  • function_left_parentheses_linter() produces a more specific lint (and no longer fails) when the opening parenthesis is on a different line than function or the call name (#1953, @MichaelChirico). Thanks also to @IndrajeetPatil and @lorenzwalthert for identifying a regression in the initial fix, #1963.

Changes to defaults

  • Set the default for the except argument in duplicate_argument_linter() to c("mutate", "transmute"). This allows sequential updates like x |> mutate(a = b + 1, a = log(a)) (#1345, @IndrajeetPatil).

  • object_usage_linter()

    • gains skip_with argument to skip code in with() expressions. To be consistent with R CMD check, it defaults to TRUE (#941, #1458, @IndrajeetPatil).
    • Handles backticked symbols inside {glue} expressions correctly, e.g. glue("{`x`}") correctly determines x was used (#1619, @MichaelChirico)
    • Detects problems inside R4.1.0+ lambda functions (\(...)) (#1933, @MichaelChirico)

  • spaces_inside_linter() allows terminal missing keyword arguments (e.g. alist(arg = ); #540, @MichaelChirico)

  • brace_linter() allows empty braced expression on the same line (e.g. while (updating_condition()) { }) regardless of allow_single_line to match the corresponding behavior in {styler}. This is an expedient while the style guide on handling this case awaits clarification: tidyverse/style#191. (#1346, @MichaelChirico)

  • undesirable_function_linter() and undesirable_operator_linter() now produce an error if empty vector of undesirable functions or operators is provided (#1867, @IndrajeetPatil).

  • New linters which are also included as defaults (see "New linters" for more details):

    • indentation_linter()
    • quotes_linter()
    • unnecessary_concatenation_linter()
    • whitespace_linter()

  • lint_package() also looks for files in exec/ (#1950, @jmaspons).

New and improved features

  • New get_r_string() helper to get the R-equivalent value of a string, especially useful for R-4-style raw strings. Previously an internal lintr helper, now exported to facilitate writing custom linters (#1493, @MichaelChirico).

  • object_usage_linter() improves lint metadata when detecting undefined infix operators, e.g. %>% or := (#1497, @MichaelChirico)

  • unused_import_linter() can detect datasets from imported packages and no longer warns when a package is imported only for its datasets (#1545, @IndrajeetPatil).

  • When a linter triggers an error, lint() will provide a more actionable summary of where the error occurred, particularly useful for cases like lint_package() where both the responsible file and the responsible linter would be unknown (@MichaelChirico).

    Typically, linters should not themselves cause R to stop -- syntax errors lead to error lints, for example. Please report such failures as they are likely bugs.

  • pipe_continuation_linter() recognizes violations involving the native R pipe |> (#1609, @MichaelChirico)

  • paste_linter() also catches usages like paste(rep("*", 10L), collapse = "") that can be written more concisely as strrep("*", 10L) (#1108, @MichaelChirico)

  • spaces_inside_linter() produces lints for spaces inside [[ (#1673, @IndrajeetPatil).

  • sprintf_linter() also applies to gettextf() (#1677, @MichaelChirico)

  • Documentation for all linters contains examples of code that does and does not produce lints (#1492, @IndrajeetPatil).

  • implicit_integer_linter() gains parameter allow_colon to skip lints on expressions like 1:10 (#1155, @MichaelChirico)

  • infix_spaces_linter() supports the native R pipe |> (#1793, @AshesITR)

  • unnecessary_concatenation_linter() (f.k.a. unneeded_concatenation_linter()) no longer lints on c(...) (i.e., passing ... in a function call) when allow_single_expression = FALSE (#1696, @MichaelChirico)

  • object_name_linter() gains parameter regexes to allow custom naming conventions (#822, #1421, @AshesITR)

  • literal_coercion_linter() reports a replacement in the lint message, e.g. code like as.integer(1) will suggest using 1L instead, and code like as.numeric(NA) will suggest using NA_real_ instead (#1439, @MichaelChirico)

  • Added format() functions for lint and lints (#1784, @AshesITR)

  • all_linters() function provides an easy way to access all available linters (#1843, @IndrajeetPatil)

  • missing_argument_linter() allows missing arguments in quote() calls (#1889, @IndrajeetPatil).

  • get_source_expressions() correctly extracts indented code chunks from R Markdown documents, which helps avoid spurious lints related to whitespace (#1945, @MichaelChirico). The convention taken is that, within each chunk, all code is anchored relative to the leftmost non-whitespace column.

  • available_linters() gives priority to tags over exclude_tags in the case of overlap. In particular, this means that available_linters(tags = "deprecated") will work to return deprecated linters without needing to specify exclude_tags (#1959, @MichaelChirico).

  • The {lintr} configuration file is now searched in the system's user configuration path; the lintr config filename can also be configured explicitly by setting the environment variable R_LINTR_LINTER_FILE (#460, @klmr)

  • Errors in the {lintr} configuration file now produce more informative error messages (#886, @AshesITR)

New linters

  • matrix_apply_linter() recommends use of dedicated rowSums(), colSums(), colMeans(), rowMeans() over apply(., MARGIN, sum) or apply(., MARGIN, mean). The recommended alternative is much more efficient and more readable (#1869, @Bisaloo).

  • unnecessary_lambda_linter(): detect unnecessary lambdas (anonymous functions), e.g. lapply(x, function(xi) sum(xi)) can be lapply(x, sum) and purrr::map(x, ~quantile(.x, 0.75, na.rm = TRUE)) can be purrr::map(x, quantile, 0.75, na.rm = TRUE). Naming probs = 0.75 can further improve readability (#1531, #1866, @MichaelChirico, @Bisaloo).

  • redundant_equals_linter() for redundant comparisons to TRUE or FALSE like is_treatment == TRUE (#1500, @MichaelChirico)

  • lengths_linter() for encouraging usage of lengths(x) instead of sapply(x, length) (and similar)

  • function_return_linter() for handling issues in function return() statements. Currently handles assignments within the return() clause, e.g. return(x <- foo()) (@MichaelChirico)

  • boolean_arithmetic_linter() for identifying places where logical aggregations are more appropriate, e.g. length(which(x == y)) == 0 is the same as !any(x == y) or even all(x != y) (@MichaelChirico)

  • for_loop_index_linter() to prevent overwriting local variables in a for loop declared like for (x in x) { ... } (@MichaelChirico)

  • is_numeric_linter() for redundant checks equivalent to is.numeric(x) such as is.numeric(x) || is.integer(x) or class(x) %in% c("numeric", "integer") (@MichaelChirico)

  • empty_assignment_linter() for identifying empty assignments like x = {} that are more clearly written as x = NULL (@MichaelChirico)

  • unnecessary_placeholder_linter() for identifying where usage of the {magrittr} placeholder . could be omitted (@MichaelChirico)

  • routine_registration_linter() for identifying native routines that don't use registration (useDynLib in the NAMESPACE; @MichaelChirico)

  • indentation_linter() for checking that the indentation conforms to 2-space Tidyverse-style (@AshesITR and @dgkf, #1411, #1792, #1898).

  • unnecessary_nested_if_linter() for checking unnecessary nested if statements where a single if statement with appropriate conditional expression would suffice (@IndrajeetPatil and @AshesITR, #1778).

  • implicit_assignment_linter() for checking implicit assignments in function calls (@IndrajeetPatil and @AshesITR, #1777).

  • quotes_linter() is a generalized version of (now deprecated) single_quotes_linter(). It accepts an argument delimiter to specify whether " or ' should be the accepted method for delimiting character literals. The default, ", reflects the Tidyverse style guide recommendation and matches the behavior of single_quotes_linter().

  • unnecessary_concatenation_linter() is simply unneeded_concatenation_linter(), renamed.

  • consecutive_assertion_linter() (f.k.a. consecutive_stopifnot_linter()) now lints for consecutive calls to assertthat::assert_that() (as long as the msg= argument is not used; #1604, @MichaelChirico).

  • whitespace_linter() is simply no_tab_linter(), renamed. In the future, we plan to extend it to work for different whitespace preferences.

Notes

  • {lintr} now depends on R version 3.5.0, in line with the tidyverse policy for R version compatibility.

  • lint() continues to support Rmarkdown documents. For users of custom .Rmd engines, e.g. marginformat from {tufte} or theorem from {bookdown}, note that those engines must be registered in {knitr} prior to running lint() in order for {lintr} to behave as expected, i.e., they should be shown as part of knitr::knit_engines$get().

    For {tufte} and {bookdown} in particular, one only needs to load the package namespace to accomplish this (i.e., minimally loadNamespace("tufte") or loadNamespace("bookdown"), respectively, will register those packages' custom engines; since library() also runs loadNamespace(), running library() will also work). Note further that {tufte} only added this code to their .onLoad() recently after our request to do so (see rstudio/tufte#117). Therefore, ensure you're using a more recent version to get the behavior described here for {tufte}.

    More generally, there is no requirement that loadNamespace() will register a package's custom {knitr} engines, so you may need to work with other package authors to figure out a solution for other engines.

    Thanks to Yihui and other developers for their helpful discussions around this issue (#797, @IndrajeetPatil).

  • The output of lint() and Lint() gain S3 class "list" to assist with S3 dispatch (#1494, @MichaelChirico)

    • As a corollary, we now register an as_tibble method for class lints, conditional on {tibble} availability, to avoid dispatching to the list method which does not work with lint() output (#1997, @MichaelChirico)

  • object_usage_linter() gives a more helpful warning when a glue() expression fails to evaluate (#1985, @MichaelChirico)

  • The documentation of object_name_linter() now describes how "symbols" works when passed to the styles parameter (#1924, @hedsnz).

lintr 3.0.2

  • Fix test to avoid leaving behind cache files in the global cache directory.

lintr 3.0.1

  • Skip multi-byte tests in non UTF-8 locales (#1504)

  • modify_defaults() no longer uses the mistaken "lintr_function" S3 class, instead applying the "linter" class also common to Linter(). Linter() also includes "function" in the S3 class of its output to facilitate S3 dispatch to function methods where appropriate (#1392, @MichaelChirico).

Changes to defaults

  • brace_linter() allows opening curly braces on a new line when there is a comment ending the preceding line (#1433 and #1434, @IndrajeetPatil).

  • seq_linter() produces lint for seq(...), since it also cannot properly handle empty edge cases (#1468, @IndrajeetPatil).

  • seq_linter() additionally lints on 1:n() (from {dplyr}) and 1:.N (from {data.table}) (#1396, @IndrajeetPatil).

  • literal_coercion_linter() lints {rlang}'s atomic vector constructors (i.e., int(), chr(), lgl(), and dbl()) if the argument is a scalar (#1437, @IndrajeetPatil).

  • redundant_ifelse_linter()'s lint message correctly suggests negation when the yes condition is 0 (#1432, @IndrajeetPatil).

  • seq_linter() provides more specific replacement code in lint message (#1475, @IndrajeetPatil).

New and improved features

  • New sort_linter() to detect x[order(x)] and recommend the faster and clearer alternative: sort(x) (#1528, @Bisaloo)

  • unreachable_code_linter() ignores trailing comments if they match a closing nolint block (#1347, @AshesITR).

  • New function_argument_linter() to enforce that arguments with defaults appear last in function declarations, see the Tidyverse design guide (#450, @AshesITR).

  • New allow_trailing argument added to assignment_linter() to check when assignment operators are at the end of a line, and the value is on the following line (#1491, @ashbaldry)

  • New sarif_output() function to output lints to SARIF output (#1424, @shaopeng-gh)

  • commented_code_linter() now lints commented argument code, containing a trailing comma, as well (#386, @AshesITR). For example a comment containing # na.rm = TRUE, now triggers a lint.

Bug fixes

  • object_length_linter() does not fail in case there are dependencies with no exports (e.g. data-only packages) (#1424, #1509, @IndrajeetPatil).
  • get_source_expressions() no longer fails on R files that match a knitr pattern (#743, #879, #1406, @AshesITR).
  • Parse error lints now appear with the linter name "error" instead of NA (#1405, @AshesITR).
    Also, linting no longer runs if the source_expressions contain invalid string data that would cause error messages in other linters. in other linters.
  • Prevent lint() from hanging on Rmd files with some syntax errors (#1443, @MichaelChirico).
  • get_source_expressions() no longer omits trailing non-code lines from knitr files (#1400, #1415, @AshesITR).
    This fixes the location information for trailing_blank_lines_linter() in RMarkdown documents without terminal newlines.
  • The vignette("lintr") incorrectly cited exclude as the key for setting file exclusions in .lintr when it is actually exclusions. (#1401, @AshesITR)
  • Fixed file exclusion detection in lint_dir() so it no longer errors if there are multiple exclusions or no global exclusions configured for a single file (#1413, #1442, @AshesITR).

Other changes

  • The minimum needed version for soft dependency {withr} has been bumped to 2.5.0 (#1404, @IndrajeetPatil).
  • Changed the deprecation warning for with_defaults() to also mention modify_defaults() (#1438, @AshesITR).
  • Quarto files (.qmd) were supported out of the box. The documentation and the testing infrastructure are updated to reflect this (#1486, @IndrajeetPatil).

lintr 3.0.0

Breaking changes

  • All linters are now function factories (i.e., functions that return functions) for consistency. Previously, only linters with customizable parameters were factories (#245, @fangly, @AshesITR, and @MichaelChirico).

    This means that usage such as lint("file.R", seq_linter) should be updated to lint("file.R", seq_linter()), and the following update for custom linters:

    my_custom_linter <- function(source_expression) { ... }

# becomes
my_custom_linter <- function() Linter(function(source_expression) { ... })

  • Exclusions specified in the .lintr file are now relative to the location of that file and support excluding entire directories (#158, #438, @AshesITR).

  • Removed long-deprecated linters (they've been marked as deprecated since v1.0.1 in 2017):

    • absolute_paths_linter()
    • camel_case_linter()
    • multiple_dots_linter()
    • snake_case_linter()
    • trailing_semicolons_linter()

  • Removed return() from all_undesirable_functions because early returns (which often improve readability and reduce code complexity) require explicit use of return(). Follow #1100 for an upcoming return_linter() to lint unnecessary return() statements (#1146, @AshesITR).

    Note that you can replicate old behavior by supplying return as a custom undesirable function: undesirable_function_linter(c(all_undesirable_functions, list(return = NA)))

Deprecations

  • Lints are now marked with the name of the linter that caused them instead of the name of their implementation function. Deprecated the obsolete linter argument of Lint() (#664, #673, #746, @AshesITR). Downstream custom linters should follow suit.
  • Renamed semicolon_terminator_linter() to semicolon_linter() for better consistency. semicolon_terminator_linter() survives but is marked for deprecation. The new linter also has a new signature, taking arguments allow_compound and allow_trailing to replace the old single argument semicolon, again for signature consistency with other linters.
  • The following linters were subsumed into brace_linter() and are now deprecated; see the item on brace_linter() below:
    • closed_curly_linter()
    • open_curly_linter()
    • paren_brace_linter()
  • The ... argument for lint(), lint_dir(), and lint_package() has been promoted to an earlier position to better match the Tidyverse design principle of data->descriptor->details. This change enables passing objects to ... without needing to specify non-required arguments, e.g. lint_dir("/path/to/dir", linter()) now works without the need to specify relative_path. This affects some code that uses positional arguments (#935, @MichaelChirico).
    • For lint(), ... is now the 3rd argument, where earlier this was cache.
    • For lint_dir() and lint_package(), ... is now the 2nd argument, where earlier this was relative_path.
  • Deprecated argument source_file to exported functions with_id() and ids_with_token(). It has been renamed to source_expression to better reflect that this argument is typically the output of get_source_expressions(). For now, the old argument source_file can still be used (with warning). The now-private functional versions of many linters also underwent the same renaming (source_file -> source_expression). This has no direct effect on packages importing lintr, but is mentioned in case custom linters imitating lintr style had also adopted the source_file naming and want to adapt to keep in sync.
  • Deprecated with_defaults() in favor of linters_with_defaults(), and add modify_defaults() which is intended to be used more generally to modify (i.e., extend, trim, and/or update) a list of defaults. Note that the argument corresponding to with_defaults()'s default= is called defaults= (i.e., pluralized) in both of these, and that usage like with_defaults(default = NULL, ...) should be converted to linters_with_defaults(defaults = list(), ...) (#1029, #1336, #1361, @AshesITR and @michaelchirico).
  • Deprecated the find_line() and find_column() helpers from the item-level expressions returned with get_source_expressions(). These helpers were typically associated with regex-based logic for building linters, which is rarely needed and prone to false positives; now that lintr almost exclusively uses XPath-based logic for linters, these are no longer necessary (#1373, @MichaelChirico).

Other changes to defaults

Updates to default_linters

  • New brace_linter() which combines several curly brace related linters, deprecating the following predecessors (#1041, @AshesITR):
    • closed_curly_linter(); both now also allow }] in addition to }) and }, as exceptions, i.e., } doesn't need to be on its own line if paired with a closing square bracket, a closing parenthesis, or a comma. Also improved lint metadata so that source markers land at the closing brace instead of the closing parenthesis to improve the experience of fixing the lint (#583, @AshesITR).
    • open_curly_linter(); both also no longer lint unnecessary trailing whitespace (use trailing_whitespace_linter() for this) and also allow (, ,, and %>% on preceding lines as exceptions, i.e., { can be alone on a line if the previous line is terminated with an opening parenthesis, a comma, or a pipe (%>%) (#487, #1028, @AshesITR).
    • paren_brace_linter(); brace_linter() also lints if/else and repeat with missing whitespace.
    • brace_linter() also newly enforces the following rules surrounding curly braces (originally Google linters, see below):
      • Require else to come on the same line as the preceding }, if present (#884, @MichaelChirico).
      • Require functions spanning multiple lines to use curly braces (#987, @MichaelChirico).
      • Require balanced usage of {} in if/else conditions, i.e., if the if branch uses braces, then so must the else branch, and vice versa (#983, @MichaelChirico).
  • New paren_body_linter() checks that there is a space between a right parenthesis and a body expression (#809, @kpagacz).
  • Added semicolon_linter() as a default because it enforces a tidyverse style guide rule (#683, @AshesITR).
  • assignment_linter() (#915, @MichaelChirico):
    • Right assignments are now linted by default (-> and ->>).
    • New argument allow_cascading_assign (TRUE by default) toggles whether to lint <<- and ->>.
    • New argument allow_right_assign (FALSE by default) toggles whether to lint -> and ->>.
  • commented_code_linter(): use the parse tree to find comments, eliminating some false positives (#451, @AshesITR).
  • equals_na_linter() (#545, @MichaelChirico):
    • Extended to lint x != NA (before, only == was caught) and NA == x (before, only NA on RHS was caught).
    • Extended to skip usages in comments like is.na(x) # use is.na(x), not x == NA.
  • function_left_parentheses_linter(): improved location information (#1266, #1267, @AshesITR).
  • infix_spaces_linter():
    • Added argument allow_multiple_spaces (TRUE by default) which toggles whether to generate a lint for operators used with multiple spaces, e.g. x + 2. The default setting allows extra spacing to be used to increase line-to-line alignment (#940, @f-ritter and @MichaelChirico).
    • Extended so that usages like a~b and function(a=1) { ... } are linted (#930, #michaelchirico).
    • Added argument exclude_operators to disable lints on selected infix operators. By default, all "low-precedence" operators throw lints; see ?infix_spaces_linter for an enumeration of these. (#914, @MichaelChirico).
    • Add an exception for / usage in box::use() declarations (#1087, @klmr).
  • line_length_linter(): place the source marker at the margin of the affected line to improve user experience during de-linting -- just press Return (#735, @AshesITR).*
  • no_tab_linter(): use more reliable matching (e.g., excluding matches found in comments; #441, @russHyde).
  • object_length_linter(): correctly detect generics and only count the implementation class towards the length. This prevents false positive lints in the case of long generic names, e.g. very_very_very_long_generic_name.short_class no longer produces a lint (#871, @AshesITR).
  • object_name_linter():
    • Improved generic detection -- in user-defined method my_method.upstream.class, upstream.class no longer throws a lint because the generic (my_method) properly uses snake_case (#737, @AshesITR).
    • Exclude special R namespace hook functions such as .onLoad() (#500, #614, @AshesITR and @MichaelChirico).
    • Correctly detect imported functions when linting packages (#642, @AshesITR).
    • Correctly detect assignment generics like names<-.class_name (#843, @jonkeane).
    • Added new styles "symbols" and "SNAKE_CASE" (#494, #495, #615, #670, @MichaelChirico and @AshesITR).
      • "symbols" is a new default style which won't lint all-symbol object names. In particular, that means operator names like %+% are allowed.
    • No longer lints names used in $ extractions (#582, @AshesITR).
  • object_usage_linter():
    • Detect global variables if there are top-level dollar-assignments (#666, @AshesITR).
    • Report usage warnings spanning multiple lines (#507, @AshesITR).
    • Detect usages inside glue::glue() constructs (#942, @AshesITR).
    • Extended to include functions assigned with = instead of <- (#1081, @MichaelChirico).
    • Detect functions exported by packages that are explicitly attached using library() or require() calls (#1127, @AshesITR).
    • Improved location information in some cases where the previous regex-based approach didn't work, e.g. unicode characters in variable names (#1285, @AshesITR).
    • Correctly detect functions declared within assign() and setMethod() (#1322, @AshesITR).
  • spaces_inside_linter(): ignore spaces preceding trailing comments (#636, @MichaelChirico).
  • T_and_F_symbol_linter():
    • Added as a default because it enforces a tidyverse style guide rule (#517, @AshesITR).
    • No longer lint occurrences of T and F when used for subsetting, and give a better message when used as variable names (#657, @AshesITR).
  • trailing_blank_lines_linter():
    • Extended to lint files without a terminal newline (#675, @AshesITR).
    • Also, running lint() on a file without a terminal newline no longer throws a warning().
  • trailing_whitespace_linter():
    • Extended to also lint completely blank lines by default (#1044, @AshesITR).
    • Added argument allow_empty_lines (FALSE by default) to toggle this behavior.
    • Improved so that trailing whitespace inside string literals does not trigger a lint (#1045, @AshesITR).
    • Added argument allow_in_strings (TRUE by default) to toggle this behavior.
  • undesirable_function_linter():
    • Added new functions to default_undesirable_functions related to debugging (#876, @MichaelChirico):
      • browser()
      • debug()
      • debugcall()
      • debugonce()
      • trace()
      • untrace()
    • No longer lints library() and require() calls attaching a package with an undesired name, e.g. library(foo) (#814, @kpagacz and @MichaelChirico).
    • No longer lints undesirable symbols if they are used as names in $ extractions (#1050, @AshesITR).
    • Added more explanation why certain functions might be undesirable and what alternatives to use; ditto for undesirable_operator_linter() (#1133, #1146, #1159, @AshesITR).

Other noteworthy changes

  • cyclocomp_linter(): set the default complexity_limit to 15. This brings the default into sync with what is enforced via default_linters (#693, @AshesITR).
  • lint_package() now lints files in the demo directory by default (#703, @dmurdoch).
  • Moved the default lintr cache directory from ~/.R/lintr_cache (which was a violation of CRAN policy) to R_user_dir("lintr", "cache"). Note that 3.0.0 is a major version update and invalidates the old cache anyway, so it can be safely deleted (#1062, @AshesITR).

New and improved features

New linters

  • backport_linter() for detecting mismatched R version dependencies (#506, #1316, #1318, #1319, @MichaelChirico and @AshesITR).
  • duplicate_argument_linter() similarly checks that there are no duplicate arguments supplied to function calls (#850, @renkun-ken).
  • missing_argument_linter() to check for empty (missing) arguments in function calls (#563, #1152, @renkun-ken and @AshesITR).
  • missing_package_linter() to check if packages in calls to library() and friends are missing (#536, #1037, @renkun-ken and @MichaelChirico).
  • namespace_linter() to check for common mistakes in pkg::symbol usages (#548, @renkun-ken).
  • package_hooks_linter() to run a series of checks also done by R CMD check on the .onLoad(), .onAttach(), .Last.lib() and .onDetach() hooks (#882, @MichaelChirico).
  • pipe_call_linter() to enforce that all steps of magrittr pipelines use explicit calls instead of symbols, e.g. x %>% mean() instead of x %>% mean (#801, @MichaelChirico).
  • sprintf_linter() to check for common mistakes in sprintf() usage (#544, #624, @renkun-ken and @AshesITR).
  • unused_import_linter() to detect unnecessary library() calls in R scripts (#239, @jimhester, @AshesITR).

Google linters

Google is a heavy user of lintr internally, and has developed a large set of linters improving code consistency and correcting common R usage mistakes. This release includes many of these linters that are of general interest to the broader R community. More will be included in future releases. See, e.g. #884, #979, #998, #1011, #1016, #1036, #1051, #1066, and #1067; special thanks to @MichaelChirico and @michaelquinn32.

  • any_duplicated_linter() Require usage of anyDuplicated(x) > 0L over any(duplicated(x)) and similar.
  • any_is_na_linter() Require usage of anyNA(x) over any(is.na(x)).
  • class_equals_linter() Prevent comparing class(x) with ==, !=, or %in%, where inherits() is typically preferred.
  • condition_message_linter() Prevent condition messages from being constructed like stop(paste(...)) (where just stop(...) is preferable).
  • conjunct_test_linter() Require usage of expect_true(x); expect_true(y) over expect_true(x && y) and similar.
  • consecutive_stopifnot_linter() Require consecutive calls to stopifnot() to be unified into one.
  • expect_comparison_linter() Require usage of expect_gt(x, y) over expect_true(x > y) and similar.
  • expect_identical_linter() Require usage of expect_identical() by default, and expect_equal() only by exception.
  • expect_length_linter() Require usage of expect_length(x, n) over expect_equal(length(x), n) and similar.
  • expect_named_linter() Require usage of expect_named(x, n) over expect_equal(names(x), n) and similar.
  • expect_not_linter() Require usage of expect_false(x) over expect_true(!x), and vice versa.
  • expect_null_linter() Require usage of expect_null(x) over expect_equal(x, NULL) and similar.
  • expect_s3_class_linter() Require usage of expect_s3_class(x, k) over expect_equal(class(x), k) and similar.
  • expect_s4_class_linter() Require usage of expect_s4_class(x, k) over expect_true(methods::is(x, k)).
  • expect_true_false_linter() Require usage of expect_true(x) over expect_equal(x, TRUE) and similar.
  • expect_type_linter() Require usage of expect_type(x, t) over expect_equal(typeof(x), t) and similar.
  • fixed_regex_linter() Require fixed = TRUE or stringr::fixed() for regular expressions that can be expressed statically, e.g. strsplit(x, "[.]") can be strsplit(x, ".", fixed = TRUE).
    • Added parameter allow_grepl (default FALSE) to toggle whether grepl() usages should be linted. These might be treated separately because grepl("^x", NA) is FALSE; the startsWith() equivalent to get FALSE for missing input is clunkier, but more explicit: !is.na(x) & startsWith(x, string) (#1376, @MichaelChirico).
  • ifelse_censor_linter() Require usage of pmax() / pmin() where appropriate, e.g. ifelse(x > y, x, y) is pmax(x, y).
  • inner_combine_linter() Require inputs to known-vectorized functions to be combined first rather than later, e.g. as.Date(c(x, y)) over c(as.Date(x), as.Date(y)).
  • literal_coercion_linter() Require using correctly-typed literals instead of direct coercion, e.g. 1L instead of as.numeric(1).
  • nested_ifelse_linter() Prevent nested calls to ifelse() like ifelse(A, x, ifelse(B, y, z)), and similar.
  • numeric_leading_zero_linter() Require a leading 0 in fractional numeric constants, e.g. 0.1 instead of .1.
  • outer_negation_linter() Require usage of !any(x) over all(!x) and !all(x) over any(!x).
  • paste_linter() lint for common mis-use of paste() and paste0():
    • paste0() encouraged instead of paste(sep = "").
    • toString() or glue::glue_collapse() encouraged instead of paste(x, collapse = ", ").
    • Lint sep= passed to paste0() -- typically a mistake.
  • redundant_ifelse_linter() Prevent usage like ifelse(A & B, TRUE, FALSE) or ifelse(C, 0, 1) (the latter is as.numeric(!C)).
  • regex_subset_linter() Require usage of grep(ptn, x, value = TRUE) over x[grep(ptn, x)] and similar.
  • string_boundary_linter() Require usage of startsWith(x, ptn) over grepl("^ptn", x) or substr(x, 1, 3) == ptn and similar.
  • strings_as_factors_linter() Check for code designed to work before and after the stringsAsFactors = FALSE default change in R 4.0 by examining code for data.frame() usages susceptible to assumptions about the default value of stringsAsFactors=.
  • system_file_linter() Prevent usage like file.path(system.file("A", package = "pkg"), "B") where simply system.file("A", "B", package = "pkg") is more concise and readable.
  • unreachable_code_linter() Prevent code after return() and stop() statements that will never be reached (extended for #1051 thanks to early user testing, thanks @bersbersbers!).
  • vector_logic_linter() Require use of scalar logical operators (&& and ||) inside if() conditions and similar.
  • yoda_test_linter() Require usage of expect_identical(x, 1L) over expect_equal(1L, x) and similar.

Other features and improvements

  • Documentation: Reorganize linter documentation into new tag-based Rd pages (#888, #1015, @AshesITR).
    • Each linter has its own help page.
    • ?linters also links to tag help pages, collecting linters with a similar goal.
    • Each linter can have multiple tags.
    • available_linters(): new function to list available linters and their tags. This feature is extensible by package authors providing add-on linters for {lintr}.
    • available_tags(): new function to list available tags.
    • linters_with_tags(): new function to help build a list of linters using tags.
  • Encodings: lintr now supports non-system character Encodings. The correct encoding is auto-detected from .Rproj or DESCRIPTION files in your project. Override the default in the encoding setting of lintr (#752, #782, @AshesITR).
  • Jenkins CI: Support for writing comments to GitHub repo when running in Jenkins CI (#488, @fdlk).
  • Performance: Optimized performance-critical functions in lintr, such as get_source_expressions() resulting in about 2x speedup in our test suite and even more for complex files (#1169, #1197, #1200, #1201, #1214, @MichaelChirico and @AshesITR). Average lint_package() execution time is down about 30% and the median package sees about 40% improvement.
  • Raw strings: Several linters tightened internal logic to allow for raw strings like R"( a\string )" (#1034, #1285, @MichaelChirico and @AshesITR).
  • Selective exclusion syntax: New syntax to exclude only selected linters from certain lines or passages. Use # nolint: linter_name, linter2_name. or # nolint start: linter_name, linter2_name. in source files or named lists of line numbers in .lintr. Note the terminal . is required. Also allows for partial matching as long as the supplied prefix is unique, e.g. # nolint: infix_spaces. works to exclude infix_spaces_linter (#605, #872, @AshesITR).
    • Added the linter name to lintrs output to facilitate discovery of the correct name (#1357, @AshesITR).
  • Improved S3 generic detection for non-standard S3 generics where UseMethod() is called after several preceding expressions (#846, @jonkeane).
  • extraction_operator_linter(): no longer lint x[NULL] (#1273, @AshesITR).
  • is_lint_level(): new exported helper for readably explaining which type of expression is required for a custom linter. Some linters are written to require the full file's parse tree (for example, single_quotes_linter()). Others only need single expressions, which is more cache-friendly (most linters are written this way to leverage caching) (#921, @MichaelChirico).
  • lint_dir() excludes the renv and packrat directories by default (#697, @AshesITR).
  • lint(): new optional argument text for supplying a line or lines directly, e.g. if the file is already in memory or linting is being done ad hoc (#503, @renkun-ken).
  • seq_linter(): improve lint message to be clearer about the reason for linting (#522, @MichaelChirico).
  • unneeded_concatenation_linter():
    • Correctly considers arguments in pipelines (%>% or |>; #573, #1270, @michaelquinn32 and @AshesITR).
    • New argument allow_single_expression, default TRUE, toggling whether c(x) should be linted, i.e., a call to c() with only one entry which is not a constant. In some such cases, c() can simply be dropped, e.g. c(a:b); in others, the parentheses are still needed, e.g. -c(a:b) should be -(a:b); and in still others, c() is used for the side-effect of stripping attributes, e.g. c(factor(letters)) or c(matrix(1:10, 5, 2)). In this last case, c() can (and should) in most cases be replaced by as.vector() or as.integer() for readability. In fact, we suspect it is always preferable to do so, and may change the default to allow_single_expression = FALSE in the future. Please report your use case if as.vector() does not suit your needs (#1344, @MichaelChirico).
  • use_lintr(): new exported helper for creating a minimal .lintr configuration (#902, @AshesITR).
  • xml_nodes_to_lints(): new exported helper for converting xml_node objects obtained using linter logic expressed in XPath into Lint objects (#1124, #1216, #1234, @MichaelChirico and @AshesITR).

Bug fixes

  • RStudio: Source markers are cleared when there are no lints (#520, @AshesITR).
  • Error message for mismatched starts and ends of exclusion ranges is now more helpful. (#571, #860, @AshesITR and @danielinteractive).
  • Improved location information for R parse errors (#894, #892, @renkun-ken and @AshesITR).
  • get_source_expressions():
    • Fix possible error on invalid XML produced by xmlparsedata::xml_parse_data() (#559, @renkun-ken).
    • Fix handling zero-length variable name error (#566, @renkun-ken).
    • Malformed Rmd files now cause a lint instead of an error (#571, @AshesITR).
    • No longer fails if getParseData() returns a truncated (invalid) Unicode character as parsed text (#815, @leogama).
    • Fixes the text value for STR_CONST nodes involving 1- or 2-width octal escapes (e.g. "\1") to account for an R parser bug (https://bugs.r-project.org/show_bug.cgi?id=18323; #1056, @MichaelChirico).
    • Handle Rmd inputs containing unevaluated code blocks with named format specifiers (#472, @russHyde).
  • line_length_linter(): fix a bug causing duplicate lints for lines containing multiple expressions (#681, @AshesITR).
  • lint_package():
    • Warns and returns NULL if no package is found (instead of giving a peculiar error message; #776, @MichaelChirico).
    • Stricter about what is considered to be a package -- folders named DESCRIPTION are ignored (#702, @MichaelChirico).
  • linters_with_defaults() (formerly with_defaults()):
    • No longer duplicates the lintr_function class when it is already present (#511, @AshesITR).
    • Warns if a named argument is NULL but its name is not in defaults (#1049, @AshesITR).
  • linters_with_defaults() handles automatic naming of very long arguments correctly (#774, @MichaelChirico).
  • save_cache() will now recursively create the cache directory; this avoids errors that could arise if any parent directories do not exist (#60, @dankessler).
  • spaces_left_parentheses_linter(): fix a bug causing warnings like "In parent == parent[before_operator_idx] longer object length is not a multiple of shorter object length" in nested expressions (#654, @AshesITR).

Internals

  • Added a new, more restrictive test workflow - test-package - that fails on warnings emitted by tests (#1263, #1272, @AshesITR).
  • Added a secondary, more restrictive lint workflow - lint-changed-files - for newly written / modified code (#641, @dragosmg).
  • Several optional Imported packages have become Suggested dependencies: httr, testthat, and rstudioapi. This should allow snappier CI builds for usages not relying on some more "peripheral" features of the package.
  • Special thanks to @bersbersbers for early testing on the 3.0.0 changes.
  • Switched CI from Travis to GitHub Actions, using the full tidyverse recommended R CMD check. Code coverage and linting are implemented using separate GitHub Actions workflows (#572, @dragosmg).
  • Updated R CMD GitHub Actions workflow to check for R 3.6 on Ubuntu, instead of R 3.3, and for R 4.0 on Windows, instead of R 3.6 (#803, @ dragosmg).
  • lintr now uses the 3rd edition of testthat (@MichaelChirico, @AshesITR, #910, #967).

lintr 2.0.1

New features

  • lintr now supports GitHub Actions and will print the lints as warning messages if lints are printed during an action.
  • lint_package() will now lint vignettes and data-raw by default (#447, @AshesITR).
  • lint_dir() will now include Rmd and Rnw files by default (@AshesITR).

Minor fixes and features

  • single_quote_linter() no longer causes a print issue when open quote appears at a column > than close quote (#457, @jamieRowen)
  • absolute_path_linter() and nonportable_path_linter() now handle file-paths that are wrapped with double-quotes (#433, #437, @russHyde).
  • get_source_expressions() has been changed to handle expr_or_assign_or_help tokens arising when parsing code containing equals-assignments in R-devel (#403, #456, @russHyde).
  • object_usage_linter has been changed to ensure lint-position is indicated relative to the start of the file, rather than the start of a defining function (#432, @russHyde).
  • commas_linter now allows spaces to come before a comma when used to denote a fall-through in a switch statement (#499, @MrMallIronmaker)

lintr 2.0.0

lintr 2.0.0 is a major release, and incorporates development changes since the last major release (1.0.0) in 2016-04-16.

Deprecated functions

  • Deprecated camel_case_linter(), snake_case_linter() and multiple_dots_linter() in favor of object_name_linter() which enforce the given style: snake_case, dotted.case, lowerCamelCalse, UpperCamelCase, alllowercase or ALLUPPERCASE (#59, @fangly).
  • Deprecated absolute_paths_linter() in favor of the new absolute_path_linter(), with a lax mode for fewer false positive lints (#199, @fangly).

New linters

  • New cyclocomp_linter() identifies overly complex functions (#361, @fabian-s)
  • New equals_na_linter() (#143, #326, @jabranham)
  • New extraction_operator_linter() checks that the [[ operator is used when extracting a single element from an object, not [ (subsetting) nor $ (interactive use) (@fangly).
  • New function_left_parentheses_linter() to check that there is no space between a function name and its left parentheses (#204, @jrnold).
  • New implicit_integer_linter() detects round numbers not declared as integers, i.e. 1 instead of 1L (@fangly).
  • New nonportable_path_linter() identifies paths constructed without file.path() (@fangly).
  • New paren_brace_linter() checks that there is a space between right parenthesis and an opening curly brace (@bfgray3, #242).
  • New pipe_continuation_linter() to ensure there is a space before %>% and newline afterwards (#216).
  • New semicolon_terminator_linter() reports semicolons at the end of a line (#147, @gaborcsardi) and between expressions (#181, @fangly).
  • New seq_linter(), finds 1:length(...) (and similar) expressions (#155, @gaborcsardi)
  • New todo_comment_linter() lints TODOs (@fangly).
  • New T_and_F_symbol_linter() warns when using T and F instead of TRUE and FALSE (@fangly).
  • New undesirable_operator_linter() and undesirable_function_linter() lint uses of user-specified functions and operators (#48, #149, @fangly).
  • New unneeded_concatenation_linter() lints uses of c() with a constant or no arguments (@fangly).

New functions for writing linters

  • Export expect_lint() (#178, #210)
  • Export ids_with_token() and with_id() (#297 @stufield)
  • linters can use the XML parse tree as well now, via the https://github.com/MangoTheCat/xmlparsedata package (#154, @gaborcsardi)

New functions for users

  • New lint_dir() function to lint files under a given directory (@arekbee, #360)
  • New summary.lints() function to summarize the linter results (#260, #262, @wlandau).
  • New checkstyle_output() function to output lints to checkstyle XML output (#156, @joshkgold)

Linter fixes

  • closed_curly_linter() now allows closing parenthesis or comma after closing curly brace (#167, @Enchufa2)
  • commas_linter() now handles missing arguments calls properly (#145)
  • commented_code_linter() now relaxed, it no longer lints comments within roxygen blocks and does not consider "-" an R operator to avoid too many false positives.
  • function_left_parentheses_linter() now allows spaces if a function starts with a left parenthesis (#311)
  • no_tab_linter() now reports proper line in all cases (#134, @fangly)
  • object_length_linter() argument length now defaults to 30 for consistency (#325 @DragosMG)
  • object_name_linter() now works when passed multiple styles (#341, @infotroph)
  • object_usage_linter() has been changed to better detect lexical scoping of global variables (#27, #336, #91, #382)
  • object_usage_linter() now respects utils::globalVariables(), so it can be used to avoid false positive warnings due to non-standard evaluation (#352)
  • object_usage_linter() now ignores top level calls that contain function definitions (#26).
  • object_linter*()s now only lint objects declared in the current file (#76, #108, #136, #191, #194, #201, @fangly).
  • open_curly_linter() and closed_curly_linter() now do not lint double curly syntax (#388)
  • open_curly_linter() now allows comments after the curly braces (#188)
  • pipe_continuation_linter() now behaves better in nested expressions, functions etc. (#366 @russHyde)
  • space_inside_linter() now reports proper line and column numbers (#203, @fangly)

General improvements and fixes

  • expect_lint() now no longer shows Rstudio markers and error messages are correctly preserved (#180, #211, @fangly)
  • Lint() / as.data.frame() error now fixed (#179, @fangly).
  • lint() no longer errors with inline \\Sexpr (#127).
  • lint() no longer errors with '<% %>' constructs (#185).
  • lint_package() now works with the cache, as intended (#146, @schloerke)
  • lint_package() now excludes R/RcppExports.R by default (#282)
  • lint_package() now removes fully excluded files as soon as possible
  • lintr now looks up its configuration in any parent directories as well as the package directory (#238, #345)
  • seq_linter is now one of the default linters (#316).
  • Fix issue in lintr's compatibility with R-devel, due to to a new version of the PCRE library (#411.)
  • read_settings() now has a better error message when the config file does not end with a newline (#160, #189)
  • expect_lint_free() is now automatically skipped when run on covr (#287)
  • Now lintr only tries to generate comments if running in wercker or travis CI (#166)
  • Add support for overriding GitHub API Token via GITHUB_TOKEN environment variable (#63, @mattyb)
  • Config files are now also searched for in the users' home directory (#266, @randy3k)
  • Fixed crash caused by ambiguous cache file paths (#212, @fangly).
  • RStudio addins to lint current source and project (fixes #264, @JhossePaul)
  • Added proper handling of tab characters (fixes #44, @fangly)
  • lintr does not need the igraph package any more (#152, @gaborcsardi)
  • Fixed cache not saved in a directory other than requested (#213, @fangly) avoid reading and pre-processing of ignored files (@mwaldstein)
  • Allow for any number of # to start a comment. Useful in ESS (#299, @prosoitos)
  • R Markdown files that do not contain chunks are no longer treated as code (#370).
  • Fixed plain-code-block bug in Rmarkdown (#252, @russHyde)
  • Fixed bug where non-R chunks using {lang} engine format were parsed from R-markdown (#322, @russHyde)
  • Ensured lintr runs / installs / tests on R-3.6: pinned to github xmlparsedata; ensure vectors are length-1 when compared using && and || (#363 #377 #384 #391, @russHyde).

lintr 1.0.3

  • Fix tests to work with changes in the parser in R 3.6

lintr 1.0.2

  • Fix tests to work with upcoming testthat release.

lintr 1.0.1

  • bugfix to work with knitr 1.16.7
  • expect_lint_free() now is always skipped on CRAN. This is necessary because the non-binary R source may not be available when running tests on CRAN, and those tests may not be run in the package directory.

lintr 1.0.0

  • bugfix to work with testthat 1.0.0

lintr 0.3.3

  • infix_spaces_linter now properly checks = in named arguments. (#130, @saurfang).
  • commas_linter now properly recognizes lints when preceded by a blank line and points to the missing space rather than the comma (#111, #129, @saurfang).
  • Make spaces_left_parentheses_linter more robust when determining ( type (#128, @saurfang)
  • commented_code_linter (#83, @jackwasey)
  • Now trims long comments (#55, reported by @paulstaab)
  • Automatic commenting of Github commits and pull requests when linting on Travis-CI
  • expect_lint_free expectation can be added to testthat unit tests.
  • Robust configuration system and exclusion logic
  • Emacs and Sublime Text 3 plugins now available from their respective package repositories.
  • add names.lints, split.lints (#49, @ttriche)
  • Fixed bug that caused vim syntastic plugin not to work properly in windows (#46, @abossenbroek)
  • allow lintr customization per project using .lintr config files.
  • use globalenv() instead of baseenv() for default parent environment so that methods will be included.
  • do not check object usage if eval fails. Fixes (#24, reported by @fabian-s)
  • trailing_whitespace_linter was reporting the incorrect line number
  • Use RStudio source marker API to display lints (#37, @jjallaire)
  • Permit single quotes if they quote literal double quotes (#28, @jackwasey)
  • # nolint comments are respected with caching (#68, @krlmlr)
  • Properly handle all knitr document formats
  • Allow for (( when linting (#259, @nathaneastwood)
  • Remove ^ from infix spaces to conform with tidyverse. (#302, @nathaneastwood)

lintr 0.2.0

  • Initial release