From 86c054168c502e2bf768983201e3b8a7da84838d Mon Sep 17 00:00:00 2001
From: Samuel Moelius <samuel.moelius@trailofbits.com>
Date: Sat, 11 Nov 2023 17:20:16 +0000
Subject: [PATCH] Simplify `overscoped_allow` path handling

---
 .../restriction/overscoped_allow/src/lib.rs   | 35 +++++++------------
 1 file changed, 13 insertions(+), 22 deletions(-)

diff --git a/examples/restriction/overscoped_allow/src/lib.rs b/examples/restriction/overscoped_allow/src/lib.rs
index 0b2ffacad..63e40b37c 100644
--- a/examples/restriction/overscoped_allow/src/lib.rs
+++ b/examples/restriction/overscoped_allow/src/lib.rs
@@ -28,7 +28,7 @@ use rustc_span::{sym, BytePos, CharPos, FileLines, FileName, RealFileName, Span,
 use rustfix::diagnostics::{Diagnostic, DiagnosticSpan};
 use serde::Deserialize;
 use std::{
-    cell::RefCell,
+    borrow::Cow,
     fs::OpenOptions,
     path::{Path, PathBuf},
 };
@@ -106,7 +106,6 @@ struct OverscopedAllow {
     metadata: OnceCell<Metadata>,
     diagnostics: Vec<Diagnostic>,
     ancestor_meta_item_span_map: FxHashMap<HirId, FxHashMap<Span, FxHashSet<Option<Span>>>>,
-    canonical_paths_cache: RefCell<FxHashMap<PathBuf, PathBuf>>,
 }
 
 impl_lint_pass!(OverscopedAllow => [OVERSCOPED_ALLOW]);
@@ -161,7 +160,6 @@ impl OverscopedAllow {
             metadata: OnceCell::new(),
             diagnostics,
             ancestor_meta_item_span_map: FxHashMap::default(),
-            canonical_paths_cache: RefCell::new(FxHashMap::default()),
         }
     }
 
@@ -336,26 +334,9 @@ impl OverscopedAllow {
             return false;
         };
         let metadata = self.metadata(&span_local_path);
-        let lhs = &span_local_path;
-        let rhs = Path::new(&diagnostic_span.file_name);
-        for path in [lhs, rhs] {
-            if_chain! {
-                if self.canonical_paths_cache.borrow().get(path).is_none();
-                if let Ok(canonical_path) = if path.is_absolute() {
-                    path.canonicalize()
-                } else {
-                    metadata.workspace_root.as_std_path().join(path).canonicalize()
-                };
-                then {
-                    self.canonical_paths_cache
-                        .borrow_mut()
-                        .insert(path.to_path_buf(), canonical_path);
-                }
-            }
-        }
+        let lhs = &absolutize(metadata, &span_local_path);
+        let rhs = &absolutize(metadata, Path::new(&diagnostic_span.file_name));
         if_chain! {
-            if let Some(lhs) = self.canonical_paths_cache.borrow().get(lhs);
-            if let Some(rhs) = self.canonical_paths_cache.borrow().get(rhs);
             if lhs == rhs;
             if let Ok(FileLines { lines, .. }) = cx.sess().source_map().span_to_lines(span);
             if let Some(first_line) = lines.first();
@@ -376,6 +357,16 @@ impl OverscopedAllow {
     }
 }
 
+fn absolutize<'a>(metadata: &Metadata, path: &'a Path) -> Cow<'a, Path> {
+    if path.is_absolute() {
+        // smoelius: `path` may not point in the workspace. It could point into `$HOME/.cargo`, for
+        // example.
+        Cow::Borrowed(path)
+    } else {
+        Cow::Owned(metadata.workspace_root.as_std_path().join(path))
+    }
+}
+
 fn include_trailing_semicolons(cx: &LateContext<'_>, mut span: Span) -> Span {
     // smoelius: I have seen `span_to_lines` fail on real code.
     let Ok(FileLines { file, .. }) = cx.sess().source_map().span_to_lines(span) else {