Use XDG config directory

NEWS.md

@@ -122,6 +122,9 @@
 
 * `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)
+
 ### 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).

R/settings.R

@@ -8,7 +8,8 @@
 #'  4. `linter_file` in the user home directory
 #'  5. [default_settings()]
 #'
-#' The default linter_file name is `.lintr` but it can be changed with option `lintr.linter_file`.
+#' The default linter_file name is `.lintr` but it can be changed with option `lintr.linter_file`
+#' or the environment variable `R_LINTR_LINTER_FILE`
 #' This file is a dcf file, see [base::read.dcf()] for details.
 #' @param filename source file to be linted
 read_settings <- function(filename) {

R/settings_utils.R

@@ -69,7 +69,9 @@ find_config <- function(filename) {
     find_config2(path),
     # User directory
     # cf: rstudio@bc9b6a5 SessionRSConnect.R#L32
-    file.path(Sys.getenv("HOME", unset = "~"), linter_file)
+    file.path(Sys.getenv("HOME", unset = "~"), linter_file),
+    # Next check for a global config file
+    file.path(R_user_dir("lintr", which = "config"), "config")
   )
 
   # Search through locations, return first valid result

R/zzz.R

@@ -279,7 +279,7 @@ settings <- NULL
 .onLoad <- function(libname, pkgname) {
   op <- options()
   op_lintr <- list(
-    lintr.linter_file = ".lintr"
+    lintr.linter_file = Sys.getenv("R_LINTR_LINTER_FILE", ".lintr")
   )
   toset <- !(names(op_lintr) %in% names(op))
   if (any(toset)) options(op_lintr[toset])

tests/testthat/test-settings.R

@@ -43,6 +43,23 @@ test_that("it uses config home directory settings if provided", {
   expect_identical(settings$exclude, "test")
 })
 
+test_that("it uses system config directory settings if provided", {
+  path <- withr::local_tempdir()
+  config_parent_path <- withr::local_tempdir("config")
+  config_path <- file.path(config_parent_path, "R", "lintr")
+  dir.create(config_path, recursive = TRUE)
+  file <- withr::local_tempfile(tmpdir = path)
+  local_config(config_path, 'exclude: "test"', filename = "config")
+
+  withr::with_envvar(c(R_USER_CONFIG_DIR = config_parent_path), lintr:::read_settings(file))
+
+  lapply(setdiff(ls(settings), "exclude"), function(setting) {
+    expect_identical(settings[[setting]], default_settings[[setting]])
+  })
+
+  expect_identical(settings$exclude, "test")
+})
+
 test_that("it errors if the config file does not end in a newline", {
   f <- withr::local_tempfile()
   cat("linters: linters_with_defaults(closed_curly_linter = NULL)", file = f)

vignettes/lintr.Rmd

@@ -91,12 +91,13 @@ exclusions: list(
 More generally, `lintr` searches for a settings file according to following prioritized list.
 The first one found, if any, will be used:
 
-1.  If `options("lintr.linter_file")` is an absolute path, this file will be used. The default for this option is `".lintr"`.
+1.  If `options("lintr.linter_file")` is an absolute path, this file will be used. The default for this option is `".lintr"` or the value of the environment variable `R_LINTR_LINTER_FILE`, if set.
 2.  A project-local linter file; that is, either
     1.  a linter file (that is, a file named like `lintr.linter_file`) in the currently-searched directory, i.e. the directory of the file passed to `lint()`; or
     2.  a linter file in the `.github/linters` child directory of the currently-searched directory.
 3.  A project-local linter file in the closest parent directory of the currently-searched directory, starting from the deepest path, moving upwards one level at a time. When run from `lint_package()`, this directory can differ for each linted file.
 4.  A linter file in the user's `HOME` directory.
+5.  A linter file called `config` in the user's configuration path (given by `tools::R_user_dir("lintr", which = "config")`).
 
 If no linter file is found, only default settings take effect (see [defaults](#defaults)).