allow config to be an .R file

R/settings.R

@@ -22,18 +22,7 @@ read_settings <- function(filename) {
     default_settings[["encoding"]] <- default_encoding
   }
 
-  if (!is.null(config_file)) {
-    malformed <- function(e) {
-      stop("Malformed config file, ensure it ends in a newline\n  ", conditionMessage(e), call. = FALSE)
-    }
-    config <- tryCatch(
-      read.dcf(config_file, all = TRUE),
-      warning = malformed,
-      error = malformed
-    )
-  } else {
-    config <- NULL
-  }
+  config <- read_config_file(config_file)
 
   for (setting in names(default_settings)) {
     value <- get_setting(setting, config, default_settings)
@@ -50,18 +39,45 @@ read_settings <- function(filename) {
   }
 }
 
+read_config_file <- function(config_file) {
+  if (is.null(config_file)) {
+    return(NULL)
+  }
+
+  if (endsWith(config_file, ".R")) {
+    config <- new.env()
+    read <- function(file) {
+      sys_source(file, config)
+      config
+    }
+    malformed <- function(e) {
+      stop("Malformed config file, ensure it is valid R syntax\n  ", conditionMessage(e), call. = FALSE)
+    }
+  } else {
+    read <- function(file) {
+      dcf_values <- read.dcf(file, all = TRUE)
+      out <- lapply(names(dcf_values), function(setting) {
+        tryCatch(
+          eval(parse(text = dcf_values[[setting]], keep.source = FALSE)),
+          error = function(e) stop("Malformed config setting '", setting, "'\n  ", conditionMessage(e), call. = FALSE)
+        )
+      })
+      names(out) <- names(dcf_values)
+      out
+    }
+    malformed <- function(e) {
+      stop("Malformed config file, ensure it ends in a newline\n  ", conditionMessage(e), call. = FALSE)
+    }
+  }
+  tryCatch(read(config_file), warning = malformed, error = malformed)
+}
+
 get_setting <- function(setting, config, defaults) {
   option <- getOption(paste(sep = ".", "lintr", setting))
   if (!is.null(option)) {
     option
   } else if (!is.null(config[[setting]])) {
-    malformed <- function(e) {
-      stop("Malformed config setting '", setting, "'\n  ", conditionMessage(e), call. = FALSE)
-    }
-    tryCatch(
-      eval(parse(text = config[[setting]])),
-      error = malformed
-    )
+    config[[setting]]
   } else {
     defaults[[setting]]
   }

R/zzz.R

@@ -277,6 +277,18 @@ default_undesirable_operators <- all_undesirable_operators[names(all_undesirable
 default_settings <- NULL
 
 settings <- NULL
+# TODO(R>=3.6.0): Just use sys.source() directly. Note that we can't
+#   write a wrapper that only passes keep.parse.data=FALSE on R>3.5.0
+#   (without doing some wizardry to evade R CMD check) because
+#   there is a check for arguments not matching the signature which
+#   will throw a false positive on R3.5.0. Luckily the argument
+#   defaults on R>=3.6.0 are dictated by global options, so we can use
+#   that for the wrapper here rather than doing some NSE tricks.
+sys_source <- function(...) {
+  old <- options(keep.source.pkgs = FALSE, keep.parse.data.pkgs = FALSE)
+  on.exit(options(old))
+  sys.source(...)
+}
 
 # nocov start
 .onLoad <- function(libname, pkgname) {
@@ -287,8 +299,10 @@ settings <- NULL
   toset <- !(names(op_lintr) %in% names(op))
   if (any(toset)) options(op_lintr[toset])
 
-  backports::import(pkgname, c("trimws", "lengths", "deparse1", "...names"))
-  # requires R>=3.6.0; see https://github.com/r-lib/backports/issues/68
+  # R>=3.6.0: str2expression, str2lang
+  # R>=4.0.0: deparse1
+  # R>=4.1.0: ...names
+  backports::import(pkgname, c("deparse1", "...names"))
   base_ns <- getNamespace("base")
   backports_ns <- getNamespace("backports")
   lintr_ns <- getNamespace(pkgname)