Google linters for 3.0.0 release

[MichaelChirico]

Splitting off a subset of #884 as a TODO list for 3.0.0 release; the rest of the linters can be done after that.

• AnyDuplicatedLinter - Require usage of anyDuplicated() > 0 over any(duplicated(.)) New any_duplicated_linter #986
• AnyIsNALinter - Require usage of anyNA over any(is.na(.)) New any_is_na_linter #975
• ClassEqualsLinter - Block comparison of class with == New class_equals_linter #989
• StopPasteLinter condition_message_linter - Block usage of paste() and paste0() with messaging functions using ... New stop_paste_linter #999
• MultipleStopifnotLinter ConsecutiveStopifnotLinter - Force consecutive stopifnot() calls into just one New consecutive_stopifnot_linter #1005
• ElseSameLineLinter - Require else to come on the same line as the preceding brace New else_same_line_linter #1002
• ExpectComparisonLinter - Require usage of expect_gt(x, y) over expect_true(x > y) (and similar) Expect comparison #955
• ExpectIdenticalLinter - Require usage of expect_identical(x, y) where appropriate New expect_identical_linter #958
• ExpectIsLinter - Redirect away from deprecated testthat::expect_is() expect_is_linter, or just use undesirable_function_linter? #946
• ExpectLengthLinter - Require usage of expect_length(x, n) over expect_equal(length(x), n) New expect_length_linter #950
• ExpectNamedLinter - Require usage of expect_named(x, n) over expect_equal(names(x), n) New expect_named_linter #949
• ExpectNotLinter - Require usage of expect_false(.) over expect_true(!.) New expect_not_linter #945
• ExpectNullLinter - Require usage of expect_null(x) over expect_equal(x, NULL) and similar expect_null_linter #887
• ExpectS3ClassLinter - Require usage of expect_s3_class() or expect_s4_class() where appropriate. expect_s3_class_linter and expect_s4_class_linter #943
• ExpectS4ClassLinter - Require usage of expect_s4_class(x, k) over expect_true(is(x, k)) expect_s3_class_linter and expect_s4_class_linter #943
• ExpectTrueFalseAndConditionLinter conjunct_test_linter - Force && conditions in expect_true(), expect_false() to be written separately New conjunct_expecation_linter #948
• ExpectTrueFalseLinter - Require usage of expect_true(x) over expect_equal(x, TRUE) New expect_true_false_linter #947
• ExpectTypeLinter - Require usage of expect_type(x, type) over expect_equal(typeof(x), type) expect_type_linter #924
• FixedRegexLinter - Require usage of 'fixed=TRUE' in regular expressions where appropriate New fixed_regex_linter #1021
• FunctionBraceLinter - Require multi-line functions to use braces New function_brace_linter #987
• IfelseCensorLinter - Block usage of ifelse where pmin or pmax is more appropriate New ifelse_censor_linter #1007
• IfElseMatchBracesLinter - Require both or neither if/else branches to use curly braces New if_else_match_braces_linter #983
• InnerCombineLinter - Require c() to be applied before relatively expensive vectorized functions New inner_combine_linter #1012
• LiteralCoercionLinter - Require usage of correctly-typed literals over literal coercions New literal_coercion_linter #995
• NestedIfelseLinter - Block usage of nested ifelse() calls New nested_ifelse_linter #996
• NumericLeadingZeroLinter - Require usage of a leading zero in all fractional numerics New numeric_leading_zero_linter #992
• OuterNegationLinter - Require usage of !any(.) over all(!.), !all(.) over any(!.) New outer_negation_linter #988
• PasteSepLinter - Block usage of paste() with sep='' New paste_sep_linter #997
• PasteToStringLinter - Block usage of paste() with collapse=', ' New paste_to_string_linter #1013
• PipeCallLinter - Force explicit calls in magrittr pipes New pipe_call_linter enforcing calls (not symbols) in magrittr pipes #801
• RedundantIfelseLinter - Prevent ifelse() from being used to produce TRUE/FALSE New redundant_ifelse_linter #1000
• GrepSubsetLinter RegexSubsetLinter - Require usage of grep(value = TRUE) over x[grep(x)] New regex_subset_linter #1004
• StopifnotAndConditionLinter conjunct_test_linter - Force && conditions in stopifnot() to be written separately Extend conjunct_expectation_linter to include stopifnot(), rename to conjunct_test_linter #1011
• StringsAsFactorsLinter - Identify cases where stringsAsFactors should be supplied explicitly New strings_as_factors_linter #1020
• SystemFileLinter - Block usage of file.path() with system.file() New system_file_linter #1006
• UnreachableCodeLinter - Block unreachable code and comments following return statements New unreachable_code_linter #1003
• VectorLogicLinter - Enforce usage of scalar && in conditional statements New vector_logic_linter #978
• YodaTestLinter - Block obvious 'yoda tests' New yoda_test_linter #957

[AshesITR]

Do we want to expose google_linters as an alternative to default_linters in 3.0.0, or hold off for now?
NB it would require changing some configuration options for some of the (default) linters IINM, so wouldn't be equivalent to linters_with_tags("google"), even if that tag was introduced (which it still should).

[MichaelChirico]

my instinct is to hold off for now... want to prioritize 3.0.0 now & don't think it's quite as straightforward to deliver this. want to think a bit more carefully as well as discuss internally what that object should be.