fix: replace panicking expect() with map_or() for edge-case file paths

PR_DESCRIPTION.md

@@ -0,0 +1,23 @@
+# Fix panic on edge-case file paths in LRU disk cache init
+
+## Problem
+
+`LruDiskCache::init()` in `src/lru_disk_cache/mod.rs` calls `.expect("Bad path?")` on `file.file_name()`, which panics if the path ends in `..` or is otherwise unusual. A build cache tool should handle unexpected file system states gracefully rather than crashing.
+
+## Root Cause
+
+`Path::file_name()` returns `None` when the path terminates in `..` or consists solely of a root or prefix. The `.expect()` call converts this into a panic. While uncommon, symlinks or filesystem corruption could produce such paths in the cache directory.
+
+## Fix
+
+Replaced `.expect("Bad path?").starts_with(TEMPFILE_PREFIX)` with `.map_or(false, |name| name.starts_with(TEMPFILE_PREFIX))`. Paths without a valid file name component are now treated as non-temporary files (skipping the cleanup branch) rather than crashing.
+
+## Testing
+
+- Create a cache directory containing a path component ending in `..`.
+- Previously: sccache panics during cache init. Now: the entry is handled gracefully.
+- Normal cache operation should be unaffected.
+
+## Impact
+
+Affects sccache users whose cache directories may contain unusual file paths. A panic in cache init prevents the entire build cache from working.

src/lru_disk_cache/mod.rs

@@ -188,8 +188,7 @@ impl LruDiskCache {
         for (file, size) in get_all_files(&self.root) {
             if file
                 .file_name()
-                .expect("Bad path?")
-                .starts_with(TEMPFILE_PREFIX)
+                .map_or(false, |name| name.starts_with(TEMPFILE_PREFIX))
             {
                 fs::remove_file(&file).unwrap_or_else(|e| {
                     error!("Error removing temporary file `{}`: {}", file.display(), e);