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 lazy_static::lazy_static;
   5 use regex::Regex;
   6 use rustc_ast::ast::LitKind;
   7 use rustc_hir::{Expr, ExprKind, PathSegment};
   8 use rustc_lint::{LateContext, LateLintPass};
   9 use rustc_middle::ty;
  10 use rustc_session::{declare_lint_pass, declare_tool_lint};
  11 use rustc_span::{source_map::Spanned, Span};
  12
  13 declare_clippy_lint! {
  14     /// **What it does:**
  15     /// Checks for calls to `ends_with` with possible file extensions
  16     /// and suggests to use a case-insensitive approach instead.
  17     ///
  18     /// **Why is this bad?**
  19     /// `ends_with` is case-sensitive and may not detect files with a valid extension.
  20     ///
  21     /// **Known problems:** None.
  22     ///
  23     /// **Example:**
  24     ///
  25     /// ```rust
  26     /// fn is_rust_file(filename: &str) -> bool {
  27     ///     filename.ends_with(".rs")
  28     /// }
  29     /// ```
  30     /// Use instead:
  31     /// ```rust
  32     /// fn is_rust_file(filename: &str) -> bool {
  33     ///     filename.rsplit('.').next().map(|ext| ext.eq_ignore_ascii_case("rs")) == Some(true)
  34     /// }
  35     /// ```
  36     pub CASE_SENSITIVE_FILE_EXTENSION_COMPARISONS,
  37     pedantic,
  38     "Checks for calls to ends_with with case-sensitive file extensions"
  39 }
  40
  41 declare_lint_pass!(CaseSensitiveFileExtensionComparisons => [CASE_SENSITIVE_FILE_EXTENSION_COMPARISONS]);
  42
  43 fn check_case_sensitive_file_extension_comparison(ctx: &LateContext<'_>, expr: &Expr<'_>) -> Option<Span> {
  44     lazy_static! {
  45         static ref RE: Regex = Regex::new(r"^\.([a-z0-9]{1,5}|[A-Z0-9]{1,5})$").unwrap();
  46     }
  47     if_chain! {
  48         if let ExprKind::MethodCall(PathSegment { ident, .. }, _, [obj, extension, ..], span) = expr.kind;
  49         if ident.as_str() == "ends_with";
  50         if let ExprKind::Lit(Spanned { node: LitKind::Str(ext_literal, ..), ..}) = extension.kind;
  51         if RE.is_match(&ext_literal.as_str());
  52         then {
  53             let mut ty = ctx.typeck_results().expr_ty(obj);
  54             ty = match ty.kind() {
  55                 ty::Ref(_, ty, ..) => ty,
  56                 _ => ty
  57             };
  58
  59             match ty.kind() {
  60                 ty::Str => {
  61                     return Some(span);
  62                 },
  63                 ty::Adt(&ty::AdtDef { did, .. }, _) => {
  64                     if match_def_path(ctx, did, &STRING) {
  65                         return Some(span);
  66                     }
  67                 },
  68                 _ => { return None; }
  69             }
  70         }
  71     }
  72     None
  73 }
  74
  75 impl LateLintPass<'tcx> for CaseSensitiveFileExtensionComparisons {
  76     fn check_expr(&mut self, ctx: &LateContext<'tcx>, expr: &'tcx Expr<'tcx>) {
  77         if let Some(span) = check_case_sensitive_file_extension_comparison(ctx, expr) {
  78             span_lint_and_help(
  79                 ctx,
  80                 CASE_SENSITIVE_FILE_EXTENSION_COMPARISONS,
  81                 span,
  82                 "case-sensitive file extension comparison",
  83                 None,
  84                 "consider using a case-insensitive comparison instead",
  85             );
  86         }
  87     }
  88 }