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lintr (development version)

Bug fixes

  • 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)

  • 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)

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)

  • 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)

  • The new indentation_linter() is part of the default linters. See "New linters" for more details.

  • For naming consistency, unneeded_concatenation_linter() has been deprecated in favor of unnecessary_concatenation_linter() (#1797, @IndrajeetPatil).

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

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)

  • 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).

New linters

  • 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).

  • 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).

Notes

  • 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}.

    However, 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)

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 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 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

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 to
  • 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 syntatic 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