reland: [VFS] Use original path when falling back to external FS

This reverts commit f0cf544d6f6fe6cbca4c07772998272d6bb433d8.

Just a small change to fix:

```
/home/buildbot/as-builder-4/llvm-clang-x86_64-expensive-checks-ubuntu/llvm-project/llvm/lib/Support/VirtualFileSystem.cpp: In static member function ‘static llvm::ErrorOr<std::unique_ptr<llvm::vfs::File> > llvm::vfs::File::getWithPath(llvm::ErrorOr<std::unique_ptr<llvm::vfs::File> >, const llvm::Twine&)’:
/home/buildbot/as-builder-4/llvm-clang-x86_64-expensive-checks-ubuntu/llvm-project/llvm/lib/Support/VirtualFileSystem.cpp:2084:10: error: could not convert ‘F’ from ‘std::unique_ptr<llvm::vfs::File>’ to ‘llvm::ErrorOr<std::unique_ptr<llvm::vfs::File> >’
   return F;
          ^
```

Differential Revision: https://reviews.llvm.org/D113832

1 files changed, 80 insertions, 27 deletions

diff --git a/llvm/lib/Support/VirtualFileSystem.cpp b/llvm/lib/Support/VirtualFileSystem.cpp
index a4abfe1..9bf0384 100644
--- a/llvm/lib/Support/VirtualFileSystem.cpp
+++ b/llvm/lib/Support/VirtualFileSystem.cpp
@@ -194,6 +194,7 @@ public:
                                                    bool RequiresNullTerminator,
                                                    bool IsVolatile) override;
   std::error_code close() override;
+  void setPath(const Twine &Path) override;
 };
 
 } // namespace
@@ -229,6 +230,12 @@ std::error_code RealFile::close() {
   return EC;
 }
 
+void RealFile::setPath(const Twine &Path) {
+  RealName = Path.str();
+  if (auto Status = status())
+    S = Status.get().copyWithNewName(Status.get(), Path);
+}
+
 namespace {
 
 /// A file system according to your operating system.
@@ -639,6 +646,8 @@ public:
   }
 
   std::error_code close() override { return {}; }
+
+  void setPath(const Twine &Path) override { RequestedName = Path.str(); }
 };
 } // namespace
 
@@ -1244,7 +1253,7 @@ directory_iterator RedirectingFileSystem::dir_begin(const Twine &Dir,
   }
 
   // Use status to make sure the path exists and refers to a directory.
-  ErrorOr<Status> S = status(Path, *Result);
+  ErrorOr<Status> S = status(Path, Dir, *Result);
   if (!S) {
     if (shouldFallBackToExternalFS(S.getError(), Result->E))
       return ExternalFS->dir_begin(Dir, EC);
@@ -1971,47 +1980,68 @@ RedirectingFileSystem::lookupPathImpl(
   return make_error_code(llvm::errc::no_such_file_or_directory);
 }
 
-static Status getRedirectedFileStatus(const Twine &Path, bool UseExternalNames,
+static Status getRedirectedFileStatus(const Twine &OriginalPath,
+                                      bool UseExternalNames,
                                       Status ExternalStatus) {
   Status S = ExternalStatus;
   if (!UseExternalNames)
-    S = Status::copyWithNewName(S, Path);
+    S = Status::copyWithNewName(S, OriginalPath);
   S.IsVFSMapped = true;
   return S;
 }
 
 ErrorOr<Status> RedirectingFileSystem::status(
-    const Twine &Path, const RedirectingFileSystem::LookupResult &Result) {
+    const Twine &CanonicalPath, const Twine &OriginalPath,
+    const RedirectingFileSystem::LookupResult &Result) {
   if (Optional<StringRef> ExtRedirect = Result.getExternalRedirect()) {
-    ErrorOr<Status> S = ExternalFS->status(*ExtRedirect);
+    SmallString<256> CanonicalRemappedPath((*ExtRedirect).str());
+    if (std::error_code EC = makeCanonical(CanonicalRemappedPath))
+      return EC;
+
+    ErrorOr<Status> S = ExternalFS->status(CanonicalRemappedPath);
     if (!S)
       return S;
+    S = Status::copyWithNewName(*S, *ExtRedirect);
     auto *RE = cast<RedirectingFileSystem::RemapEntry>(Result.E);
-    return getRedirectedFileStatus(Path, RE->useExternalName(UseExternalNames),
-                                   *S);
+    return getRedirectedFileStatus(OriginalPath,
+                                   RE->useExternalName(UseExternalNames), *S);
   }
 
   auto *DE = cast<RedirectingFileSystem::DirectoryEntry>(Result.E);
-  return Status::copyWithNewName(DE->getStatus(), Path);
+  return Status::copyWithNewName(DE->getStatus(), CanonicalPath);
 }
 
-ErrorOr<Status> RedirectingFileSystem::status(const Twine &Path_) {
-  SmallString<256> Path;
-  Path_.toVector(Path);
+ErrorOr<Status>
+RedirectingFileSystem::getExternalStatus(const Twine &CanonicalPath,
+                                         const Twine &OriginalPath) const {
+  if (auto Result = ExternalFS->status(CanonicalPath)) {
+    return Result.get().copyWithNewName(Result.get(), OriginalPath);
+  } else {
+    return Result.getError();
+  }
+}
 
-  if (std::error_code EC = makeCanonical(Path))
+ErrorOr<Status> RedirectingFileSystem::status(const Twine &OriginalPath) {
+  SmallString<256> CanonicalPath;
+  OriginalPath.toVector(CanonicalPath);
+
+  if (std::error_code EC = makeCanonical(CanonicalPath))
     return EC;
 
-  ErrorOr<RedirectingFileSystem::LookupResult> Result = lookupPath(Path);
+  ErrorOr<RedirectingFileSystem::LookupResult> Result =
+      lookupPath(CanonicalPath);
   if (!Result) {
-    if (shouldFallBackToExternalFS(Result.getError()))
-      return ExternalFS->status(Path);
+    if (shouldFallBackToExternalFS(Result.getError())) {
+      return getExternalStatus(CanonicalPath, OriginalPath);
+    }
     return Result.getError();
   }
 
-  ErrorOr<Status> S = status(Path, *Result);
-  if (!S && shouldFallBackToExternalFS(S.getError(), Result->E))
-    S = ExternalFS->status(Path);
+  ErrorOr<Status> S = status(CanonicalPath, OriginalPath, *Result);
+  if (!S && shouldFallBackToExternalFS(S.getError(), Result->E)) {
+    return getExternalStatus(CanonicalPath, OriginalPath);
+  }
+
   return S;
 }
 
@@ -2036,22 +2066,39 @@ public:
   }
 
   std::error_code close() override { return InnerFile->close(); }
+
+  void setPath(const Twine &Path) override { S = S.copyWithNewName(S, Path); }
 };
 
 } // namespace
 
 ErrorOr<std::unique_ptr<File>>
-RedirectingFileSystem::openFileForRead(const Twine &Path_) {
-  SmallString<256> Path;
-  Path_.toVector(Path);
+File::getWithPath(ErrorOr<std::unique_ptr<File>> Result, const Twine &P) {
+  if (!Result)
+    return Result;
 
-  if (std::error_code EC = makeCanonical(Path))
+  ErrorOr<std::unique_ptr<File>> F = std::move(*Result);
+  auto Name = F->get()->getName();
+  if (Name && Name.get() != P.str())
+    F->get()->setPath(P);
+  return F;
+}
+
+ErrorOr<std::unique_ptr<File>>
+RedirectingFileSystem::openFileForRead(const Twine &OriginalPath) {
+  SmallString<256> CanonicalPath;
+  OriginalPath.toVector(CanonicalPath);
+
+  if (std::error_code EC = makeCanonical(CanonicalPath))
     return EC;
 
-  ErrorOr<RedirectingFileSystem::LookupResult> Result = lookupPath(Path);
+  ErrorOr<RedirectingFileSystem::LookupResult> Result =
+      lookupPath(CanonicalPath);
   if (!Result) {
     if (shouldFallBackToExternalFS(Result.getError()))
-      return ExternalFS->openFileForRead(Path);
+      return File::getWithPath(ExternalFS->openFileForRead(CanonicalPath),
+                               OriginalPath);
+
     return Result.getError();
   }
 
@@ -2059,12 +2106,18 @@ RedirectingFileSystem::openFileForRead(const Twine &Path_) {
     return make_error_code(llvm::errc::invalid_argument);
 
   StringRef ExtRedirect = *Result->getExternalRedirect();
+  SmallString<256> CanonicalRemappedPath(ExtRedirect.str());
+  if (std::error_code EC = makeCanonical(CanonicalRemappedPath))
+    return EC;
+
   auto *RE = cast<RedirectingFileSystem::RemapEntry>(Result->E);
 
-  auto ExternalFile = ExternalFS->openFileForRead(ExtRedirect);
+  auto ExternalFile = File::getWithPath(
+      ExternalFS->openFileForRead(CanonicalRemappedPath), ExtRedirect);
   if (!ExternalFile) {
     if (shouldFallBackToExternalFS(ExternalFile.getError(), Result->E))
-      return ExternalFS->openFileForRead(Path);
+      return File::getWithPath(ExternalFS->openFileForRead(CanonicalPath),
+                               OriginalPath);
     return ExternalFile;
   }
 
@@ -2074,7 +2127,7 @@ RedirectingFileSystem::openFileForRead(const Twine &Path_) {
 
   // FIXME: Update the status with the name and VFSMapped.
   Status S = getRedirectedFileStatus(
-      Path, RE->useExternalName(UseExternalNames), *ExternalStatus);
+      OriginalPath, RE->useExternalName(UseExternalNames), *ExternalStatus);
   return std::unique_ptr<File>(
       std::make_unique<FileWithFixedStatus>(std::move(*ExternalFile), S));
 }