Move CaseSensitiveFileExtensionComparisons into Methods lint pass

Author: Jarcho

clippy_lints/src/case_sensitive_file_extension_comparisons.rs

@@ -64,7 +64,6 @@ store.register_lints(&[
     cargo::NEGATIVE_FEATURE_NAMES,
     cargo::REDUNDANT_FEATURE_NAMES,
     cargo::WILDCARD_DEPENDENCIES,
-    case_sensitive_file_extension_comparisons::CASE_SENSITIVE_FILE_EXTENSION_COMPARISONS,
     casts::AS_UNDERSCORE,
     casts::BORROW_AS_PTR,
     casts::CAST_ABS_TO_UNSIGNED,
@@ -285,6 +284,7 @@ store.register_lints(&[
     methods::BIND_INSTEAD_OF_MAP,
     methods::BYTES_COUNT_TO_LEN,
     methods::BYTES_NTH,
+    methods::CASE_SENSITIVE_FILE_EXTENSION_COMPARISONS,
     methods::CHARS_LAST_CMP,
     methods::CHARS_NEXT_CMP,
     methods::CLONED_INSTEAD_OF_COPIED,

clippy_lints/src/lib.register_lints.rs

@@ -4,7 +4,6 @@
 
 store.register_group(true, "clippy::pedantic", Some("clippy_pedantic"), vec![
     LintId::of(attrs::INLINE_ALWAYS),
-    LintId::of(case_sensitive_file_extension_comparisons::CASE_SENSITIVE_FILE_EXTENSION_COMPARISONS),
     LintId::of(casts::BORROW_AS_PTR),
     LintId::of(casts::CAST_LOSSLESS),
     LintId::of(casts::CAST_POSSIBLE_TRUNCATION),
@@ -56,6 +55,7 @@ store.register_group(true, "clippy::pedantic", Some("clippy_pedantic"), vec![
     LintId::of(matches::MATCH_WILDCARD_FOR_SINGLE_VARIANTS),
     LintId::of(matches::MATCH_WILD_ERR_ARM),
     LintId::of(matches::SINGLE_MATCH_ELSE),
+    LintId::of(methods::CASE_SENSITIVE_FILE_EXTENSION_COMPARISONS),
     LintId::of(methods::CLONED_INSTEAD_OF_COPIED),
     LintId::of(methods::FILTER_MAP_NEXT),
     LintId::of(methods::FLAT_MAP_OPTION),

clippy_lints/src/lib.register_pedantic.rs

@@ -181,7 +181,6 @@ mod bool_assert_comparison;
 mod booleans;
 mod borrow_deref_ref;
 mod cargo;
-mod case_sensitive_file_extension_comparisons;
 mod casts;
 mod checked_conversions;
 mod cognitive_complexity;
@@ -852,9 +851,6 @@ pub fn register_plugins(store: &mut rustc_lint::LintStore, sess: &Session, conf:
     store.register_late_pass(|| Box::new(strings::StringToString));
     store.register_late_pass(|| Box::new(zero_sized_map_values::ZeroSizedMapValues));
     store.register_late_pass(|| Box::new(vec_init_then_push::VecInitThenPush::default()));
-    store.register_late_pass(|| {
-        Box::new(case_sensitive_file_extension_comparisons::CaseSensitiveFileExtensionComparisons)
-    });
     store.register_late_pass(|| Box::new(redundant_slicing::RedundantSlicing));
     store.register_late_pass(|| Box::new(from_str_radix_10::FromStrRadix10));
     store.register_late_pass(move || Box::new(if_then_some_else_none::IfThenSomeElseNone::new(msrv)));

clippy_lints/src/lib.rs

@@ -0,0 +1,41 @@
+use clippy_utils::diagnostics::span_lint_and_help;
+use clippy_utils::ty::is_type_diagnostic_item;
+use if_chain::if_chain;
+use rustc_ast::ast::LitKind;
+use rustc_hir::{Expr, ExprKind};
+use rustc_lint::LateContext;
+use rustc_span::{source_map::Spanned, symbol::sym, Span};
+
+use super::CASE_SENSITIVE_FILE_EXTENSION_COMPARISONS;
+
+pub(super) fn check<'tcx>(
+    cx: &LateContext<'tcx>,
+    expr: &'tcx Expr<'_>,
+    call_span: Span,
+    recv: &'tcx Expr<'_>,
+    arg: &'tcx Expr<'_>,
+) {
+    if_chain! {
+        if let Some(method_id) = cx.typeck_results().type_dependent_def_id(expr.hir_id);
+        if let Some(impl_id) = cx.tcx.impl_of_method(method_id);
+        if cx.tcx.type_of(impl_id).is_str();
+        if let ExprKind::Lit(Spanned { node: LitKind::Str(ext_literal, ..), ..}) = arg.kind;
+        if (2..=6).contains(&ext_literal.as_str().len());
+        let ext_str = ext_literal.as_str();
+        if ext_str.starts_with('.');
+        if ext_str.chars().skip(1).all(|c| c.is_uppercase() || c.is_ascii_digit())
+            || ext_str.chars().skip(1).all(|c| c.is_lowercase() || c.is_ascii_digit());
+        let recv_ty = cx.typeck_results().expr_ty(recv).peel_refs();
+        if recv_ty.is_str() || is_type_diagnostic_item(cx, recv_ty, sym::String);
+        then {
+            span_lint_and_help(
+                cx,
+                CASE_SENSITIVE_FILE_EXTENSION_COMPARISONS,
+                call_span,
+                "case-sensitive file extension comparison",
+                None,
+                "consider using a case-insensitive comparison instead",
+            );
+        }
+    }
+}

clippy_lints/src/methods/case_sensitive_file_extension_comparisons.rs

@@ -2,6 +2,7 @@ mod bind_instead_of_map;
 mod bytecount;
 mod bytes_count_to_len;
 mod bytes_nth;
+mod case_sensitive_file_extension_comparisons;
 mod chars_cmp;
 mod chars_cmp_with_unwrap;
 mod chars_last_cmp;
@@ -2428,6 +2429,34 @@ declare_clippy_lint! {
     "Using `bytes().count()` when `len()` performs the same functionality"
 }
 
+declare_clippy_lint! {
+    /// ### What it does
+    /// Checks for calls to `ends_with` with possible file extensions
+    /// and suggests to use a case-insensitive approach instead.
+    ///
+    /// ### Why is this bad?
+    /// `ends_with` is case-sensitive and may not detect files with a valid extension.
+    ///
+    /// ### Example
+    /// ```rust
+    /// fn is_rust_file(filename: &str) -> bool {
+    ///     filename.ends_with(".rs")
+    /// }
+    /// ```
+    /// Use instead:
+    /// ```rust
+    /// fn is_rust_file(filename: &str) -> bool {
+    ///     let filename = std::path::Path::new(filename);
+    ///     filename.extension()
+    ///         .map_or(false, |ext| ext.eq_ignore_ascii_case("rs"))
+    /// }
+    /// ```
+    #[clippy::version = "1.51.0"]
+    pub CASE_SENSITIVE_FILE_EXTENSION_COMPARISONS,
+    pedantic,
+    "Checks for calls to ends_with with case-sensitive file extensions"
+}
+
 pub struct Methods {
     avoid_breaking_exported_api: bool,
     msrv: Option<RustcVersion>,
@@ -2534,6 +2563,7 @@ impl_lint_pass!(Methods => [
     ITER_ON_EMPTY_COLLECTIONS,
     NAIVE_BYTECOUNT,
     BYTES_COUNT_TO_LEN,
+    CASE_SENSITIVE_FILE_EXTENSION_COMPARISONS,
 ]);
 
 /// Extracts a method call name, args, and `Span` of the method name.
@@ -2801,6 +2831,10 @@ impl Methods {
                 ("drain", [arg]) => {
                     iter_with_drain::check(cx, expr, recv, span, arg);
                 },
+                ("ends_with", [arg]) => {
+                    if let ExprKind::MethodCall(_, _, span) = expr.kind {
+                    case_sensitive_file_extension_comparisons::check(cx, expr, span, recv, arg);
+                },
                 ("expect", [_]) => match method_call(recv) {
                     Some(("ok", [recv], _)) => ok_expect::check(cx, expr, recv),
                     Some(("err", [recv], err_span)) => err_expect::check(cx, expr, recv, self.msrv, span, err_span),