New object_overwrite_linter

DESCRIPTION

@@ -143,6 +143,7 @@ Collate:
     'nzchar_linter.R'
     'object_length_linter.R'
     'object_name_linter.R'
+    'object_overwrite_linter.R'
     'object_usage_linter.R'
     'one_call_pipe_linter.R'
     'outer_negation_linter.R'

NAMESPACE

@@ -105,6 +105,7 @@ export(numeric_leading_zero_linter)
 export(nzchar_linter)
 export(object_length_linter)
 export(object_name_linter)
+export(object_overwrite_linter)
 export(object_usage_linter)
 export(one_call_pipe_linter)
 export(open_curly_linter)

R/object_overwrite_linter.R

@@ -0,0 +1,114 @@
+#' Block assigning any variables whose name clashes with a `base` R function
+#'
+#' Re-using existing names creates a risk of subtle error best avoided.
+#'   Avoiding this practice also encourages using better, more descriptive names.
+#'
+#' @param packages Character vector of packages to search for names that should
+#'   be avoided. Defaults to the most common default packages: base, stats,
+#'   utils, tools, methods, graphics, and grDevices.
+#' @param allow_names Character vector of object names to ignore, i.e., which
+#'   are allowed to collide with exports from `packages`.
+#'
+#' @examples
+#' # will produce lints
+#' code <- "function(x) {\n  data <- x\n  data\n}"
+#' writeLines(code)
+#' lint(
+#'   text = code,
+#'   linters = object_overwrite_linter()
+#' )
+#'
+#' code <- "function(x) {\n  lint <- 'fun'\n  lint\n}"
+#' writeLines(code)
+#' lint(
+#'   text = code,
+#'   linters = object_overwrite_linter(packages = "lintr")
+#' )
+#'
+#' # okay
+#' code <- "function(x) {\n  data('mtcars')\n}"
+#' writeLines(code)
+#' lint(
+#'   text = code,
+#'   linters = object_overwrite_linter()
+#' )
+#'
+#' code <- "function(x) {\n  data <- x\n  data\n}"
+#' writeLines(code)
+#' lint(
+#'   text = code,
+#'   linters = object_overwrite_linter(packages = "base")
+#' )
+#'
+#' # names in function signatures are ignored
+#' lint(
+#'   text = "function(data) data <- subset(data, x > 0)",
+#'   linters = object_overwrite_linter()
+#' )
+#'
+#' @evalRd rd_tags("object_overwrite_linter")
+#' @seealso
+#'  - [linters] for a complete list of linters available in lintr.
+#'  - <https://style.tidyverse.org/syntax.html#object-names>
+#' @export
+object_overwrite_linter <- function(
+    packages = c("base", "stats", "utils", "tools", "methods", "graphics", "grDevices"),
+    allow_names = character()) {
+  for (package in packages) {
+    if (!requireNamespace(package, quietly = TRUE)) {
+      stop("Package '", package, "' is not available.")
+    }
+  }
+  pkg_exports <- lapply(
+    packages,
+    # .__C__ etc.: drop 150+ "virtual" names since they are very unlikely to appear anyway
+    function(pkg) setdiff(grep("^[.]__[A-Z]__", getNamespaceExports(pkg), value = TRUE, invert = TRUE), allow_names)
+  )
+  pkg_exports <- data.frame(
+    package = rep(packages, lengths(pkg_exports)),
+    name = unlist(pkg_exports),
+    stringsAsFactors = FALSE
+  )
+
+  # test that the symbol doesn't match an argument name in the function
+  # NB: data.table := has parse token LEFT_ASSIGN as well
+  xpath <- glue("
+    //SYMBOL[
+      not(text() = ancestor::expr/preceding-sibling::SYMBOL_FORMALS/text())
+      and ({ xp_text_in_table(pkg_exports$name) })
+    ]/
+      parent::expr[
+        count(*) = 1
+        and (
+          following-sibling::LEFT_ASSIGN[text() != ':=']
+          or following-sibling::EQ_ASSIGN
+          or preceding-sibling::RIGHT_ASSIGN
+        )
+        and ancestor::*[
+          (self::expr or self::expr_or_assign_or_help or self::equal_assign)
+          and (preceding-sibling::FUNCTION or preceding-sibling::OP-LAMBDA)
+        ]
+      ]
+  ")
+
+  Linter(function(source_expression) {
+    if (!is_lint_level(source_expression, "expression")) {
+      return(list())
+    }
+
+    xml <- source_expression$xml_parsed_content
+
+    bad_expr <- xml_find_all(xml, xpath)
+    bad_symbol <- xml_text(xml_find_first(bad_expr, "SYMBOL"))
+    source_pkg <- pkg_exports$package[match(bad_symbol, pkg_exports$name)]
+    lint_message <-
+      sprintf("'%s' is an exported object from package '%s'. Avoid re-using such symbols.", bad_symbol, source_pkg)
+
+    xml_nodes_to_lints(
+      bad_expr,
+      source_expression = source_expression,
+      lint_message = lint_message,
+      type = "warning"
+    )
+  })
+}

inst/lintr/linters.csv

@@ -62,6 +62,7 @@ numeric_leading_zero_linter,style consistency readability
 nzchar_linter,efficiency best_practices consistency
 object_length_linter,style readability default configurable executing
 object_name_linter,style consistency default configurable executing
+object_overwrite_linter,best_practices robustness readability configurable executing
 object_usage_linter,style readability correctness default executing configurable
 one_call_pipe_linter,style readability
 open_curly_linter,defunct