src/tools/clippy/clippy_lints/src/case_sensitive_file_extension_comparisons.rs

   1 use crate::utils::paths::STRING;
   2 use crate::utils::{match_def_path, span_lint_and_help};
   3 use if_chain::if_chain;
   4 use rustc_ast::ast::LitKind;
   5 use rustc_hir::{Expr, ExprKind, PathSegment};
   6 use rustc_lint::{LateContext, LateLintPass};
   7 use rustc_middle::ty;
   8 use rustc_session::{declare_lint_pass, declare_tool_lint};
   9 use rustc_span::{source_map::Spanned, Span};
  10
  11 declare_clippy_lint! {
  12     /// **What it does:**
  13     /// Checks for calls to `ends_with` with possible file extensions
  14     /// and suggests to use a case-insensitive approach instead.
  15     ///
  16     /// **Why is this bad?**
  17     /// `ends_with` is case-sensitive and may not detect files with a valid extension.
  18     ///
  19     /// **Known problems:** None.
  20     ///
  21     /// **Example:**
  22     ///
  23     /// ```rust
  24     /// fn is_rust_file(filename: &str) -> bool {
  25     ///     filename.ends_with(".rs")
  26     /// }
  27     /// ```
  28     /// Use instead:
  29     /// ```rust
  30     /// fn is_rust_file(filename: &str) -> bool {
  31     ///     filename.rsplit('.').next().map(|ext| ext.eq_ignore_ascii_case("rs")) == Some(true)
  32     /// }
  33     /// ```
  34     pub CASE_SENSITIVE_FILE_EXTENSION_COMPARISONS,
  35     pedantic,
  36     "Checks for calls to ends_with with case-sensitive file extensions"
  37 }
  38
  39 declare_lint_pass!(CaseSensitiveFileExtensionComparisons => [CASE_SENSITIVE_FILE_EXTENSION_COMPARISONS]);
  40
  41 fn check_case_sensitive_file_extension_comparison(ctx: &LateContext<'_>, expr: &Expr<'_>) -> Option<Span> {
  42     if_chain! {
  43         if let ExprKind::MethodCall(PathSegment { ident, .. }, _, [obj, extension, ..], span) = expr.kind;
  44         if ident.as_str() == "ends_with";
  45         if let ExprKind::Lit(Spanned { node: LitKind::Str(ext_literal, ..), ..}) = extension.kind;
  46         if (2..=6).contains(&ext_literal.as_str().len());
  47         if ext_literal.as_str().starts_with('.');
  48         if ext_literal.as_str().chars().skip(1).all(|c| c.is_uppercase() || c.is_digit(10))
  49             || ext_literal.as_str().chars().skip(1).all(|c| c.is_lowercase() || c.is_digit(10));
  50         then {
  51             let mut ty = ctx.typeck_results().expr_ty(obj);
  52             ty = match ty.kind() {
  53                 ty::Ref(_, ty, ..) => ty,
  54                 _ => ty
  55             };
  56
  57             match ty.kind() {
  58                 ty::Str => {
  59                     return Some(span);
  60                 },
  61                 ty::Adt(&ty::AdtDef { did, .. }, _) => {
  62                     if match_def_path(ctx, did, &STRING) {
  63                         return Some(span);
  64                     }
  65                 },
  66                 _ => { return None; }
  67             }
  68         }
  69     }
  70     None
  71 }
  72
  73 impl LateLintPass<'tcx> for CaseSensitiveFileExtensionComparisons {
  74     fn check_expr(&mut self, ctx: &LateContext<'tcx>, expr: &'tcx Expr<'tcx>) {
  75         if let Some(span) = check_case_sensitive_file_extension_comparison(ctx, expr) {
  76             span_lint_and_help(
  77                 ctx,
  78                 CASE_SENSITIVE_FILE_EXTENSION_COMPARISONS,
  79                 span,
  80                 "case-sensitive file extension comparison",
  81                 None,
  82                 "consider using a case-insensitive comparison instead",
  83             );
  84         }
  85     }
  86 }