limit extensions to 2-3 chars and add configuration

Author: y21

CHANGELOG.md

@@ -5575,5 +5575,6 @@ Released 2018-09-13
 [`allow-one-hash-in-raw-strings`]: https://doc.rust-lang.org/clippy/lint_configuration.html#allow-one-hash-in-raw-strings
 [`absolute-paths-max-segments`]: https://doc.rust-lang.org/clippy/lint_configuration.html#absolute-paths-max-segments
 [`absolute-paths-allowed-crates`]: https://doc.rust-lang.org/clippy/lint_configuration.html#absolute-paths-allowed-crates
+[`allowed-file-extensions`]: https://doc.rust-lang.org/clippy/lint_configuration.html#allowed-file-extensions
 [`enforce-iter-loop-reborrow`]: https://doc.rust-lang.org/clippy/lint_configuration.html#enforce-iter-loop-reborrow
 <!-- end autogenerated links to configuration documentation -->

book/src/lint_configuration.md

@@ -751,6 +751,16 @@ Which crates to allow absolute paths from
 * [`absolute_paths`](https://rust-lang.github.io/rust-clippy/master/index.html#absolute_paths)
 
 
+## `allowed-file-extensions`
+Additional file extensions to allow
+
+**Default Value:** `{}` (`rustc_data_structures::fx::FxHashSet<String>`)
+
+---
+**Affected lints:**
+* [`path_ends_with_ext`](https://rust-lang.github.io/rust-clippy/master/index.html#path_ends_with_ext)
+
+
 ## `enforce-iter-loop-reborrow`
 #### Example
 ```

clippy_lints/src/lib.rs

@@ -661,12 +661,24 @@ pub fn register_plugins(store: &mut rustc_lint::LintStore, sess: &Session, conf:
     let allow_unwrap_in_tests = conf.allow_unwrap_in_tests;
     let suppress_restriction_lint_in_const = conf.suppress_restriction_lint_in_const;
     store.register_late_pass(move |_| Box::new(approx_const::ApproxConstant::new(msrv())));
+    let allowed_file_extensions = conf
+        .allowed_file_extensions
+        .iter()
+        .cloned()
+        .chain(
+            methods::DEFAULT_ALLOWED_FILE_EXTENSIONS
+                .iter()
+                .copied()
+                .map(ToOwned::to_owned),
+        )
+        .collect::<FxHashSet<_>>();
     store.register_late_pass(move |_| {
         Box::new(methods::Methods::new(
             avoid_breaking_exported_api,
             msrv(),
             allow_expect_in_tests,
             allow_unwrap_in_tests,
+            allowed_file_extensions.clone(),
         ))
     });
     store.register_late_pass(move |_| Box::new(matches::Matches::new(msrv())));

clippy_lints/src/methods/mod.rs

@@ -121,6 +121,8 @@ use clippy_utils::msrvs::{self, Msrv};
 use clippy_utils::ty::{contains_ty_adt_constructor_opaque, implements_trait, is_copy, is_type_diagnostic_item};
 use clippy_utils::{contains_return, is_bool, is_trait_method, iter_input_pats, peel_blocks, return_ty};
 use if_chain::if_chain;
+pub use path_ends_with_ext::DEFAULT_ALLOWED_FILE_EXTENSIONS;
+use rustc_data_structures::fx::FxHashSet;
 use rustc_hir as hir;
 use rustc_hir::{Expr, ExprKind, Node, Stmt, StmtKind, TraitItem, TraitItemKind};
 use rustc_hir_analysis::hir_ty_to_ty;
@@ -3568,6 +3570,13 @@ declare_clippy_lint! {
     /// ### What it does
     /// Looks for calls to `Path::ends_with` calls where the argument looks like a file extension.
     ///
+    /// By default, Clippy has a short list of known filenames that start with a dot
+    /// but aren't necessarily file extensions (e.g. the `.git` folder), which are allowed by default.
+    /// File extensions are often two to three characters long, so this only lints in those cases
+    /// in an attempt to avoid false positives.
+    /// The `allowed-file-extensions` configuration can be used to allow additional
+    /// file extensions that Clippy should not lint.
+    ///
     /// ### Why is this bad?
     /// This doesn't actually compare file extensions. Rather, `ends_with` compares the given argument
     /// to the last **component** of the path and checks if it matches exactly.
@@ -3597,6 +3606,7 @@ pub struct Methods {
     msrv: Msrv,
     allow_expect_in_tests: bool,
     allow_unwrap_in_tests: bool,
+    allowed_file_extensions: FxHashSet<String>,
 }
 
 impl Methods {
@@ -3606,12 +3616,14 @@ impl Methods {
         msrv: Msrv,
         allow_expect_in_tests: bool,
         allow_unwrap_in_tests: bool,
+        allowed_file_extensions: FxHashSet<String>,
     ) -> Self {
         Self {
             avoid_breaking_exported_api,
             msrv,
             allow_expect_in_tests,
             allow_unwrap_in_tests,
+            allowed_file_extensions,
         }
     }
 }
@@ -4008,7 +4020,7 @@ impl Methods {
                     if let ExprKind::MethodCall(.., span) = expr.kind {
                         case_sensitive_file_extension_comparisons::check(cx, expr, span, recv, arg);
                     }
-                    path_ends_with_ext::check(cx, recv, arg, expr, &self.msrv);
+                    path_ends_with_ext::check(cx, recv, arg, expr, &self.msrv, &self.allowed_file_extensions);
                 },
                 ("expect", [_]) => {
                     match method_call(recv) {

clippy_lints/src/methods/path_ends_with_ext.rs

@@ -5,18 +5,30 @@ use clippy_utils::msrvs::Msrv;
 use clippy_utils::source::snippet;
 use clippy_utils::ty::is_type_diagnostic_item;
 use rustc_ast::{LitKind, StrStyle};
+use rustc_data_structures::fx::FxHashSet;
 use rustc_errors::Applicability;
 use rustc_hir::{Expr, ExprKind};
 use rustc_lint::LateContext;
 use rustc_span::sym;
 use std::fmt::Write;
 
-pub(super) fn check(cx: &LateContext<'_>, recv: &Expr<'_>, path: &Expr<'_>, expr: &Expr<'_>, msrv: &Msrv) {
+pub const DEFAULT_ALLOWED_FILE_EXTENSIONS: &[&str] = &["git", "svn", "gem", "npm", "vim", "env", "rnd", "ssh", "vnc"];
+
+pub(super) fn check(
+    cx: &LateContext<'_>,
+    recv: &Expr<'_>,
+    path: &Expr<'_>,
+    expr: &Expr<'_>,
+    msrv: &Msrv,
+    allowed_paths: &FxHashSet<String>,
+) {
     if is_type_diagnostic_item(cx, cx.typeck_results().expr_ty(recv).peel_refs(), sym::Path)
         && !path.span.from_expansion()
         && let ExprKind::Lit(lit) = path.kind
         && let LitKind::Str(path, StrStyle::Cooked) = lit.node
         && let Some(path) = path.as_str().strip_prefix('.')
+        && (path.len() == 2 || path.len() == 3)
+        && !allowed_paths.contains(path)
     {
         let mut sugg = snippet(cx, recv.span, "..").into_owned();
         if msrv.meets(msrvs::OPTION_IS_SOME_AND) {

clippy_lints/src/utils/conf.rs

@@ -561,6 +561,11 @@ define_Conf! {
     /// Which crates to allow absolute paths from
     (absolute_paths_allowed_crates: rustc_data_structures::fx::FxHashSet<String> =
         rustc_data_structures::fx::FxHashSet::default()),
+    /// Lint: PATH_ENDS_WITH_EXT.
+    ///
+    /// Additional file extensions to allow
+    (allowed_file_extensions: rustc_data_structures::fx::FxHashSet<String> =
+        rustc_data_structures::fx::FxHashSet::default()),
     /// Lint: EXPLICIT_ITER_LOOP
     ///
     /// Whether to recommend using implicit into iter for reborrowed values.

tests/ui-toml/toml_unknown_key/conf_unknown_key.stderr

@@ -10,6 +10,7 @@ error: error reading Clippy's configuration file: unknown field `foobar`, expect
            allow-print-in-tests
            allow-private-module-inception
            allow-unwrap-in-tests
+           allowed-file-extensions
            allowed-idents-below-min-chars
            allowed-scripts
            arithmetic-side-effects-allowed
@@ -82,6 +83,7 @@ error: error reading Clippy's configuration file: unknown field `barfoo`, expect
            allow-print-in-tests
            allow-private-module-inception
            allow-unwrap-in-tests
+           allowed-file-extensions
            allowed-idents-below-min-chars
            allowed-scripts
            arithmetic-side-effects-allowed

tests/ui/path_ends_with_ext.fixed

@@ -11,6 +11,12 @@ fn test(path: &Path) {
     path.extension().is_some_and(|ext| ext == "md");
     //~^ ERROR: this looks like a failed attempt at checking for the file extension
 
+    // some "extensions" are allowed by default
+    path.ends_with(".git");
+
+    // most legitimate "dotfiles" are longer than 3 chars, so we allow them as well
+    path.ends_with(".bashrc");
+
     path.ends_with(arg!());
 }
 

tests/ui/path_ends_with_ext.rs

@@ -11,6 +11,12 @@ fn test(path: &Path) {
     path.ends_with(".md");
     //~^ ERROR: this looks like a failed attempt at checking for the file extension
 
+    // some "extensions" are allowed by default
+    path.ends_with(".git");
+
+    // most legitimate "dotfiles" are longer than 3 chars, so we allow them as well
+    path.ends_with(".bashrc");
+
     path.ends_with(arg!());
 }
 

tests/ui/path_ends_with_ext.stderr

@@ -8,7 +8,7 @@ LL |     path.ends_with(".md");
    = help: to override `-D warnings` add `#[allow(clippy::path_ends_with_ext)]`
 
 error: this looks like a failed attempt at checking for the file extension
-  --> $DIR/path_ends_with_ext.rs:19:5
+  --> $DIR/path_ends_with_ext.rs:25:5
    |
 LL |     path.ends_with(".md")
    |     ^^^^^^^^^^^^^^^^^^^^^ help: try: `path.extension().map_or(false, |ext| ext == "md")`