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Use a slightly altered isS3stdGeneric() to detect non-standard generics #857

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merged 6 commits into from
May 23, 2022
Merged

Use a slightly altered isS3stdGeneric() to detect non-standard generics #857

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f1edf83
Change to is_s3_generic and a test
jonkeane Sep 13, 2021
de24ab2
Allow `is_s3_generic` in all versions of R
jonkeane Sep 14, 2021
251e174
:newspaper:
jonkeane Sep 16, 2021
3917dec
dont use tail; add a test
MichaelChirico May 21, 2022
0bb7f23
Merge branch 'master' into generics-detection-846
MichaelChirico May 22, 2022
9d091d5
Merge branch 'main' into generics-detection-846
MichaelChirico May 23, 2022
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1 change: 1 addition & 0 deletions NEWS.md
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Original file line number Diff line number Diff line change
Expand Up @@ -180,6 +180,7 @@ function calls. (#850, #851, @renkun-ken)
* `object_usage_linter()` now detects functions exported by packages that are explicitly attached using `library()` or `require()` calls (#1127, @AshesITR)
* New helper `xml_nodes_to_lints()` for converting `xml_node` objects obtained using linter logic expressed in XPath into `Lint` objects (#1124, @michaelchirico)
* Added more explanation why certain functions and operators might be undesirable and what alternatives to use (#1133, #1146, #1159, @AshesITR)
* Improved S3 generic detection for non-standard S3 generics (#846, @jonkeane)

# lintr 2.0.1

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15 changes: 8 additions & 7 deletions R/namespace.R
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Expand Up @@ -36,13 +36,14 @@ imported_s3_generics <- function(ns_imports) {
}

is_s3_generic <- function(fun) {
if (getRversion() >= "3.5.0") {
# Available in 3.4.0, but bugged there in multiple ways that cause errors
# throughout many base functions, e.g. `-`, `as.null.default`, `dontCheck`
utils::isS3stdGeneric(fun)
} else {
is.function(fun) # nocov
}
# Inspired by `utils::isS3stdGeneric`, though it will detect functions that
# have `useMethod()` in places other than the first expression.
bdexpr <- body(fun)
while (is.call(bdexpr) && bdexpr[[1L]] == "{") bdexpr <- bdexpr[[length(bdexpr)]]
ret <- is.call(bdexpr) && identical(bdexpr[[1L]], as.name("UseMethod"))
if (ret)
names(ret) <- bdexpr[[2L]]
ret
}

.base_s3_generics <- c(
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17 changes: 17 additions & 0 deletions tests/testthat/test-namespace.R
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@@ -0,0 +1,17 @@
test_that("is_s3_generic", {
func <- function(x) {
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print(x)
UseMethod("func")
}
Comment on lines +2 to +5
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Is there a valid use case for the other way around?
i.e. for

func <- function(x) {
  x <- UseMethod("func")
  common_postprocessing(x)
}

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let's try & keep close to the base definition unless there's a compelling reason? i'm also a bit hesitant for this change if it's not being suggested upstream as well

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The base definition checks the first call, so would find my example iinm. That's why I'm asking.

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isn't the call that's found <- though, not UseMethod?

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Ah, right. I wonder why base R looks for the first call instead of the last, then...

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I didn't see anything about isS3stdGeneric() on r-devel in a quick search... maybe worth bringing up there.

cc @moodymudskipper who identified the bug fix at root in #1161


expect_true(is_s3_generic(func))
})

test_that("is_s3_generic doesn't error for namespace-qualified calls", {
func <- function(...) {
pkg::call()
}

expect_warning(result <- is_s3_generic(func), NA)
expect_false(result)
})