[clang] [clang Dependency Scanning] Enhance File Caching Diagnostics (PR #144105)

[Jan Svoboda via cfe-commits]

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@@ -220,13 +221,34 @@ class DependencyScanningFilesystemSharedCache {
   CacheShard &getShardForFilename(StringRef Filename) const;
   CacheShard &getShardForUID(llvm::sys::fs::UniqueID UID) const;
 
-  /// Visits all cached entries and re-stat an entry using FS if
-  /// it is negatively stat cached. If re-stat succeeds on a path,
-  /// the path is added to InvalidPaths, indicating that the cache
-  /// may have erroneously negatively cached it. The caller can then
-  /// use InvalidPaths to issue diagnostics.
-  std::vector<StringRef>
-  getInvalidNegativeStatCachedPaths(llvm::vfs::FileSystem &UnderlyingFS) const;
+  struct OutOfDateEntry {
+    // A null terminated string that contains a path.
+    const char *Path = nullptr;
+
+    struct NegativelyCachedInfo {};
+    struct SizeChangedInfo {
+      uint64_t CachedSize = 0;
+      uint64_t ActualSize = 0;
+    };
+
+    std::variant<NegativelyCachedInfo, SizeChangedInfo> Info;
+
+    OutOfDateEntry(const char *Path)
+        : Path(Path), Info(NegativelyCachedInfo{}) {}
+
+    OutOfDateEntry(const char *Path, uint64_t CachedSize, uint64_t ActualSize)
+        : Path(Path), Info(SizeChangedInfo{CachedSize, ActualSize}) {}
+  };
+
+  /// Visits all cached entries and re-stat an entry using UnderlyingFS to check
+  /// if the cache contains out-of-date entries. An entry can be out-of-date for
+  /// two reasons:
+  ///  1. The entry contains a stat error, indicating the file did not exist
+  ///     in the cache, but the file exists on the UnderlyingFS.
+  ///  2. The entry is associated with a file whose size is different from the
+  ///     size of the file on the same path on the UnderlyingFS.
+  std::vector<OutOfDateEntry>
+  getInvalidEntryDiagInfo(llvm::vfs::FileSystem &UnderlyingFS) const;
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jansvoboda11 wrote:

Maybe `getOutOfDateEntries` or something?

https://github.com/llvm/llvm-project/pull/144105