src/tools/clippy/clippy_lints/src/path_buf_push_overwrite.rs

   1 use crate::utils::{match_type, paths, span_lint_and_sugg, walk_ptrs_ty};
   2 use if_chain::if_chain;
   3 use rustc_ast::ast::LitKind;
   4 use rustc_errors::Applicability;
   5 use rustc_hir::{Expr, ExprKind};
   6 use rustc_lint::{LateContext, LateLintPass};
   7 use rustc_session::{declare_lint_pass, declare_tool_lint};
   8 use std::path::{Component, Path};
   9
  10 declare_clippy_lint! {
  11     /// **What it does:*** Checks for [push](https://doc.rust-lang.org/std/path/struct.PathBuf.html#method.push)
  12     /// calls on `PathBuf` that can cause overwrites.
  13     ///
  14     /// **Why is this bad?** Calling `push` with a root path at the start can overwrite the
  15     /// previous defined path.
  16     ///
  17     /// **Known problems:** None.
  18     ///
  19     /// **Example:**
  20     /// ```rust
  21     /// use std::path::PathBuf;
  22     ///
  23     /// let mut x = PathBuf::from("/foo");
  24     /// x.push("/bar");
  25     /// assert_eq!(x, PathBuf::from("/bar"));
  26     /// ```
  27     /// Could be written:
  28     ///
  29     /// ```rust
  30     /// use std::path::PathBuf;
  31     ///
  32     /// let mut x = PathBuf::from("/foo");
  33     /// x.push("bar");
  34     /// assert_eq!(x, PathBuf::from("/foo/bar"));
  35     /// ```
  36     pub PATH_BUF_PUSH_OVERWRITE,
  37     nursery,
  38     "calling `push` with file system root on `PathBuf` can overwrite it"
  39 }
  40
  41 declare_lint_pass!(PathBufPushOverwrite => [PATH_BUF_PUSH_OVERWRITE]);
  42
  43 impl<'tcx> LateLintPass<'tcx> for PathBufPushOverwrite {
  44     fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>) {
  45         if_chain! {
  46             if let ExprKind::MethodCall(ref path, _, ref args, _) = expr.kind;
  47             if path.ident.name == sym!(push);
  48             if args.len() == 2;
  49             if match_type(cx, walk_ptrs_ty(cx.typeck_results().expr_ty(&args[0])), &paths::PATH_BUF);
  50             if let Some(get_index_arg) = args.get(1);
  51             if let ExprKind::Lit(ref lit) = get_index_arg.kind;
  52             if let LitKind::Str(ref path_lit, _) = lit.node;
  53             if let pushed_path = Path::new(&*path_lit.as_str());
  54             if let Some(pushed_path_lit) = pushed_path.to_str();
  55             if pushed_path.has_root();
  56             if let Some(root) = pushed_path.components().next();
  57             if root == Component::RootDir;
  58             then {
  59                 span_lint_and_sugg(
  60                     cx,
  61                     PATH_BUF_PUSH_OVERWRITE,
  62                     lit.span,
  63                     "calling `push` with '/' or '\\' (file system root) will overwrite the previous path definition",
  64                     "try",
  65                     format!("\"{}\"", pushed_path_lit.trim_start_matches(|c| c == '/' || c == '\\')),
  66                     Applicability::MachineApplicable,
  67                 );
  68             }
  69         }
  70     }
  71 }