Revert "[VFS] RedirectingFileSystem only replace path if not already mapped"

This reverts commit 3fda0ed, which
breaks crash reproducers in very specific circumstances. Specifically,
since crash reproducers have `UseExternalNames` set to false, the
`File->getFileEntry().getDir()->getName()` call in `DoFrameworkLookup`
would use the *cached* directory name instead of the directory of the
looked-up file.

The plan is to re-commit this patch but to *add*
`ExposesExternalVFSPath` rather than replace `IsVFSMapped`.

Differential Revision: https://reviews.llvm.org/D123103

Author: bnbarham

clang/lib/Basic/FileManager.cpp

@@ -274,15 +274,12 @@ FileManager::getFileRef(StringRef Filename, bool openFile, bool CacheFailure) {
   if (!UFE)
     UFE = new (FilesAlloc.Allocate()) FileEntry();
 
-  // FIXME: This should just check `!Status.ExposesExternalVFSPath`, but the
-  // else branch also ends up fixing up relative paths to be the actually
-  // looked up absolute path. This isn't necessarily desired, but does seem to
-  // be relied on in some clients.
   if (Status.getName() == Filename) {
     // The name matches. Set the FileEntry.
     NamedFileEnt->second = FileEntryRef::MapValue(*UFE, DirInfo);
   } else {
-    // We need a redirect. First grab the actual entry we want to return.
+    // Name mismatch. We need a redirect. First grab the actual entry we want
+    // to return.
     //
     // This redirection logic intentionally leaks the external name of a
     // redirected file that uses 'use-external-name' in \a
@@ -292,11 +289,9 @@ FileManager::getFileRef(StringRef Filename, bool openFile, bool CacheFailure) {
     //
     // FIXME: This is pretty complicated. It's also inconsistent with how
     // "real" filesystems behave and confuses parts of clang expect to see the
-    // name-as-accessed on the \a FileEntryRef. To remove this we should
-    // implement the FIXME on `ExposesExternalVFSPath`, ie. update the
-    // `FileEntryRef::getName()` path to *always* be the virtual path and have
-    // clients request the external path only when required through a separate
-    // API.
+    // name-as-accessed on the \a FileEntryRef. Maybe the returned \a
+    // FileEntryRef::getName() could return the accessed name unmodified, but
+    // make the external name available via a separate API.
     auto &Redirection =
         *SeenFileEntries
              .insert({Status.getName(), FileEntryRef::MapValue(*UFE, DirInfo)})
@@ -317,16 +312,13 @@ FileManager::getFileRef(StringRef Filename, bool openFile, bool CacheFailure) {
   FileEntryRef ReturnedRef(*NamedFileEnt);
   if (ReusingEntry) { // Already have an entry with this inode, return it.
 
-    // FIXME: This hack ensures that `getDir()` will use the path that was
-    // used to lookup this file, even if we found a file by different path
-    // first. This is required in order to find a module's structure when its
-    // headers/module map are mapped in the VFS.
-    //
-    // This should be removed once `HeaderSearch` is updated to use `*Ref`s
-    // *and* the redirection hack above is removed. The removal of the latter
-    // is required since otherwise the ref will have the exposed external VFS
-    // path still.
-    if (&DirInfo.getDirEntry() != UFE->Dir && Status.ExposesExternalVFSPath)
+    // FIXME: this hack ensures that if we look up a file by a virtual path in
+    // the VFS that the getDir() will have the virtual path, even if we found
+    // the file by a 'real' path first. This is required in order to find a
+    // module's structure when its headers/module map are mapped in the VFS.
+    // We should remove this as soon as we can properly support a file having
+    // multiple names.
+    if (&DirInfo.getDirEntry() != UFE->Dir && Status.IsVFSMapped)
       UFE->Dir = &DirInfo.getDirEntry();
 
     // Always update LastRef to the last name by which a file was accessed.

clang/test/VFS/external-names-multi-overlay.c

@@ -55,19 +55,8 @@ class Status {
   llvm::sys::fs::perms Perms;
 
 public:
-  /// Whether this entity has an external path different from the virtual path,
-  /// and the external path is exposed by leaking it through the abstraction.
-  /// For example, a RedirectingFileSystem will set this for paths where
-  /// UseExternalName is true.
-  ///
-  /// FIXME: Currently the external path is exposed by replacing the virtual
-  /// path in this Status object. Instead, we should leave the path in the
-  /// Status intact (matching the requested virtual path), and just use this
-  /// flag as hint that a new API, FileSystem::getExternalVFSPath(), will not
-  /// return `None`. Clients can then request the external path only where
-  /// needed (e.g. for diagnostics, or to report discovered dependencies to
-  /// external tools).
-  bool ExposesExternalVFSPath = false;
+  // FIXME: remove when files support multiple names
+  bool IsVFSMapped = false;
 
   Status() = default;
   Status(const llvm::sys::fs::file_status &Status);

llvm/include/llvm/Support/VirtualFileSystem.h

@@ -2163,16 +2163,10 @@ RedirectingFileSystem::lookupPathImpl(
 static Status getRedirectedFileStatus(const Twine &OriginalPath,
                                       bool UseExternalNames,
                                       Status ExternalStatus) {
-  // The path has been mapped by some nested VFS, don't override it with the
-  // original path.
-  if (ExternalStatus.ExposesExternalVFSPath)
-    return ExternalStatus;
-
   Status S = ExternalStatus;
   if (!UseExternalNames)
     S = Status::copyWithNewName(S, OriginalPath);
-  else
-    S.ExposesExternalVFSPath = true;
+  S.IsVFSMapped = true;
   return S;
 }
 
@@ -2274,9 +2268,7 @@ class FileWithFixedStatus : public File {
 
 ErrorOr<std::unique_ptr<File>>
 File::getWithPath(ErrorOr<std::unique_ptr<File>> Result, const Twine &P) {
-  // See \c getRedirectedFileStatus - don't update path if it's already been
-  // mapped.
-  if (!Result || (*Result)->status()->ExposesExternalVFSPath)
+  if (!Result)
     return Result;
 
   ErrorOr<std::unique_ptr<File>> F = std::move(*Result);

llvm/lib/Support/VirtualFileSystem.cpp

@@ -1442,20 +1442,20 @@ TEST_F(VFSFromYAMLTest, MappedFiles) {
   ErrorOr<vfs::Status> S = O->status("//root/file1");
   ASSERT_FALSE(S.getError());
   EXPECT_EQ("//root/foo/bar/a", S->getName());
-  EXPECT_TRUE(S->ExposesExternalVFSPath);
+  EXPECT_TRUE(S->IsVFSMapped);
 
   ErrorOr<vfs::Status> SLower = O->status("//root/foo/bar/a");
   EXPECT_EQ("//root/foo/bar/a", SLower->getName());
   EXPECT_TRUE(S->equivalent(*SLower));
-  EXPECT_FALSE(SLower->ExposesExternalVFSPath);
+  EXPECT_FALSE(SLower->IsVFSMapped);
 
   // file after opening
   auto OpenedF = O->openFileForRead("//root/file1");
   ASSERT_FALSE(OpenedF.getError());
   auto OpenedS = (*OpenedF)->status();
   ASSERT_FALSE(OpenedS.getError());
   EXPECT_EQ("//root/foo/bar/a", OpenedS->getName());
-  EXPECT_TRUE(OpenedS->ExposesExternalVFSPath);
+  EXPECT_TRUE(OpenedS->IsVFSMapped);
 
   // directory
   S = O->status("//root/");
@@ -1467,43 +1467,43 @@ TEST_F(VFSFromYAMLTest, MappedFiles) {
   S = O->status("//root/mappeddir");
   ASSERT_FALSE(S.getError());
   EXPECT_TRUE(S->isDirectory());
-  EXPECT_TRUE(S->ExposesExternalVFSPath);
+  EXPECT_TRUE(S->IsVFSMapped);
   EXPECT_TRUE(S->equivalent(*O->status("//root/foo/bar")));
 
   SLower = O->status("//root/foo/bar");
   EXPECT_EQ("//root/foo/bar", SLower->getName());
   EXPECT_TRUE(S->equivalent(*SLower));
-  EXPECT_FALSE(SLower->ExposesExternalVFSPath);
+  EXPECT_FALSE(SLower->IsVFSMapped);
 
   // file in remapped directory
   S = O->status("//root/mappeddir/a");
   ASSERT_FALSE(S.getError());
-  EXPECT_FALSE(S->isDirectory());
-  EXPECT_TRUE(S->ExposesExternalVFSPath);
-  EXPECT_EQ("//root/foo/bar/a", S->getName());
+  ASSERT_FALSE(S->isDirectory());
+  ASSERT_TRUE(S->IsVFSMapped);
+  ASSERT_EQ("//root/foo/bar/a", S->getName());
 
   // file in remapped directory, with use-external-name=false
   S = O->status("//root/mappeddir2/a");
   ASSERT_FALSE(S.getError());
-  EXPECT_FALSE(S->isDirectory());
-  EXPECT_FALSE(S->ExposesExternalVFSPath);
-  EXPECT_EQ("//root/mappeddir2/a", S->getName());
+  ASSERT_FALSE(S->isDirectory());
+  ASSERT_TRUE(S->IsVFSMapped);
+  ASSERT_EQ("//root/mappeddir2/a", S->getName());
 
   // file contents in remapped directory
   OpenedF = O->openFileForRead("//root/mappeddir/a");
   ASSERT_FALSE(OpenedF.getError());
   OpenedS = (*OpenedF)->status();
   ASSERT_FALSE(OpenedS.getError());
   EXPECT_EQ("//root/foo/bar/a", OpenedS->getName());
-  EXPECT_TRUE(OpenedS->ExposesExternalVFSPath);
+  EXPECT_TRUE(OpenedS->IsVFSMapped);
 
   // file contents in remapped directory, with use-external-name=false
   OpenedF = O->openFileForRead("//root/mappeddir2/a");
   ASSERT_FALSE(OpenedF.getError());
   OpenedS = (*OpenedF)->status();
   ASSERT_FALSE(OpenedS.getError());
   EXPECT_EQ("//root/mappeddir2/a", OpenedS->getName());
-  EXPECT_FALSE(OpenedS->ExposesExternalVFSPath);
+  EXPECT_TRUE(OpenedS->IsVFSMapped);
 
   // broken mapping
   EXPECT_EQ(O->status("//root/file2").getError(),
@@ -1535,20 +1535,20 @@ TEST_F(VFSFromYAMLTest, MappedRoot) {
   ErrorOr<vfs::Status> S = O->status("//mappedroot/a");
   ASSERT_FALSE(S.getError());
   EXPECT_EQ("//root/foo/bar/a", S->getName());
-  EXPECT_TRUE(S->ExposesExternalVFSPath);
+  EXPECT_TRUE(S->IsVFSMapped);
 
   ErrorOr<vfs::Status> SLower = O->status("//root/foo/bar/a");
   EXPECT_EQ("//root/foo/bar/a", SLower->getName());
   EXPECT_TRUE(S->equivalent(*SLower));
-  EXPECT_FALSE(SLower->ExposesExternalVFSPath);
+  EXPECT_FALSE(SLower->IsVFSMapped);
 
   // file after opening
   auto OpenedF = O->openFileForRead("//mappedroot/a");
   ASSERT_FALSE(OpenedF.getError());
   auto OpenedS = (*OpenedF)->status();
   ASSERT_FALSE(OpenedS.getError());
   EXPECT_EQ("//root/foo/bar/a", OpenedS->getName());
-  EXPECT_TRUE(OpenedS->ExposesExternalVFSPath);
+  EXPECT_TRUE(OpenedS->IsVFSMapped);
 
   EXPECT_EQ(0, NumDiagnostics);
 }
@@ -1696,12 +1696,12 @@ TEST_F(VFSFromYAMLTest, ReturnsRequestedPathVFSMiss) {
   auto OpenedS = (*OpenedF)->status();
   ASSERT_FALSE(OpenedS.getError());
   EXPECT_EQ("a", OpenedS->getName());
-  EXPECT_FALSE(OpenedS->ExposesExternalVFSPath);
+  EXPECT_FALSE(OpenedS->IsVFSMapped);
 
   auto DirectS = RemappedFS->status("a");
   ASSERT_FALSE(DirectS.getError());
   EXPECT_EQ("a", DirectS->getName());
-  EXPECT_FALSE(DirectS->ExposesExternalVFSPath);
+  EXPECT_FALSE(DirectS->IsVFSMapped);
 
   EXPECT_EQ(0, NumDiagnostics);
 }
@@ -1736,12 +1736,12 @@ TEST_F(VFSFromYAMLTest, ReturnsExternalPathVFSHit) {
   auto OpenedS = (*OpenedF)->status();
   ASSERT_FALSE(OpenedS.getError());
   EXPECT_EQ("realname", OpenedS->getName());
-  EXPECT_TRUE(OpenedS->ExposesExternalVFSPath);
+  EXPECT_TRUE(OpenedS->IsVFSMapped);
 
   auto DirectS = FS->status("vfsname");
   ASSERT_FALSE(DirectS.getError());
   EXPECT_EQ("realname", DirectS->getName());
-  EXPECT_TRUE(DirectS->ExposesExternalVFSPath);
+  EXPECT_TRUE(DirectS->IsVFSMapped);
 
   EXPECT_EQ(0, NumDiagnostics);
 }
@@ -1776,12 +1776,12 @@ TEST_F(VFSFromYAMLTest, ReturnsInternalPathVFSHit) {
   auto OpenedS = (*OpenedF)->status();
   ASSERT_FALSE(OpenedS.getError());
   EXPECT_EQ("vfsname", OpenedS->getName());
-  EXPECT_FALSE(OpenedS->ExposesExternalVFSPath);
+  EXPECT_TRUE(OpenedS->IsVFSMapped);
 
   auto DirectS = FS->status("vfsname");
   ASSERT_FALSE(DirectS.getError());
   EXPECT_EQ("vfsname", DirectS->getName());
-  EXPECT_FALSE(DirectS->ExposesExternalVFSPath);
+  EXPECT_TRUE(DirectS->IsVFSMapped);
 
   EXPECT_EQ(0, NumDiagnostics);
 }