[llvm][vfs] Avoid silent fallback to process-wide working directory

In createPhysicalFileSystem, preserve the per-instance working
directory, even after the first call to getcwd fails.

rdar://108213753

Differential Revision: https://reviews.llvm.org/D149173

Author: benlangmuir

llvm/lib/Support/VirtualFileSystem.cpp

@@ -257,12 +257,12 @@ class RealFileSystem : public FileSystem {
   explicit RealFileSystem(bool LinkCWDToProcess) {
     if (!LinkCWDToProcess) {
       SmallString<128> PWD, RealPWD;
-      if (llvm::sys::fs::current_path(PWD))
-        return; // Awful, but nothing to do here.
-      if (llvm::sys::fs::real_path(PWD, RealPWD))
-        WD = {PWD, PWD};
+      if (std::error_code EC = llvm::sys::fs::current_path(PWD))
+        WD = EC;
+      else if (llvm::sys::fs::real_path(PWD, RealPWD))
+        WD = WorkingDirectory{PWD, PWD};
       else
-        WD = {PWD, RealPWD};
+        WD = WorkingDirectory{PWD, RealPWD};
     }
   }
 
@@ -284,10 +284,10 @@ class RealFileSystem : public FileSystem {
   // If this FS has its own working dir, use it to make Path absolute.
   // The returned twine is safe to use as long as both Storage and Path live.
   Twine adjustPath(const Twine &Path, SmallVectorImpl<char> &Storage) const {
-    if (!WD)
+    if (!WD || !*WD)
       return Path;
     Path.toVector(Storage);
-    sys::fs::make_absolute(WD->Resolved, Storage);
+    sys::fs::make_absolute(WD->get().Resolved, Storage);
     return Storage;
   }
 
@@ -297,7 +297,7 @@ class RealFileSystem : public FileSystem {
     // The current working directory, with links resolved. (readlink .).
     SmallString<128> Resolved;
   };
-  std::optional<WorkingDirectory> WD;
+  std::optional<llvm::ErrorOr<WorkingDirectory>> WD;
 };
 
 } // namespace
@@ -323,8 +323,10 @@ RealFileSystem::openFileForRead(const Twine &Name) {
 }
 
 llvm::ErrorOr<std::string> RealFileSystem::getCurrentWorkingDirectory() const {
+  if (WD && *WD)
+    return std::string(WD->get().Specified.str());
   if (WD)
-    return std::string(WD->Specified.str());
+    return WD->getError();
 
   SmallString<128> Dir;
   if (std::error_code EC = llvm::sys::fs::current_path(Dir))
@@ -345,7 +347,7 @@ std::error_code RealFileSystem::setCurrentWorkingDirectory(const Twine &Path) {
     return std::make_error_code(std::errc::not_a_directory);
   if (auto Err = llvm::sys::fs::real_path(Absolute, Resolved))
     return Err;
-  WD = {Absolute, Resolved};
+  WD = WorkingDirectory{Absolute, Resolved};
   return std::error_code();
 }
 

llvm/unittests/Support/VirtualFileSystemTest.cpp

@@ -7,6 +7,7 @@
 //===----------------------------------------------------------------------===//
 
 #include "llvm/Support/VirtualFileSystem.h"
+#include "llvm/ADT/ScopeExit.h"
 #include "llvm/Config/llvm-config.h"
 #include "llvm/Support/Errc.h"
 #include "llvm/Support/MemoryBuffer.h"
@@ -526,6 +527,31 @@ TEST(VirtualFileSystemTest, MultipleWorkingDirs) {
   ASSERT_EQ(CIt, vfs::directory_iterator());
 }
 
+TEST(VirtualFileSystemTest, PhysicalFileSystemWorkingDirFailure) {
+  TempDir D2("d2", /*Unique*/ true);
+  SmallString<128> WD, PrevWD;
+  ASSERT_EQ(sys::fs::current_path(PrevWD), std::error_code());
+  ASSERT_EQ(sys::fs::createUniqueDirectory("d1", WD), std::error_code());
+  ASSERT_EQ(sys::fs::set_current_path(WD), std::error_code());
+  auto Restore =
+      llvm::make_scope_exit([&] { sys::fs::set_current_path(PrevWD); });
+
+  // Delete the working directory to create an error.
+  ASSERT_EQ(sys::fs::remove_directories(WD), std::error_code());
+
+  // Verify that we still get two separate working directories.
+  auto FS1 = vfs::createPhysicalFileSystem();
+  auto FS2 = vfs::createPhysicalFileSystem();
+  ASSERT_EQ(FS1->getCurrentWorkingDirectory().getError(),
+            errc::no_such_file_or_directory);
+  ASSERT_EQ(FS1->setCurrentWorkingDirectory(D2.path()), std::error_code());
+  ASSERT_EQ(FS1->getCurrentWorkingDirectory().get(), D2.path());
+  EXPECT_EQ(FS2->getCurrentWorkingDirectory().getError(),
+            errc::no_such_file_or_directory);
+  SmallString<128> WD2;
+  EXPECT_EQ(sys::fs::current_path(WD2), errc::no_such_file_or_directory);
+}
+
 TEST(VirtualFileSystemTest, BrokenSymlinkRealFSIteration) {
   TempDir TestDirectory("virtual-file-system-test", /*Unique*/ true);
   IntrusiveRefCntPtr<vfs::FileSystem> FS = vfs::getRealFileSystem();