[llvm] Use the underlying VFS when constructing RedirectingFileSystem

[jansvoboda11]

When the root node of the RedirectingFileSystem is to be resolved to the current working directory, we previously consulted the real FS instead of the provided underlying VFS. This PR fixes that issue.

[llvmbot]

@llvm/pr-subscribers-llvm-support

Author: Jan Svoboda (jansvoboda11)

Changes

When the root node of the RedirectingFileSystem is to be resolved to the current working directory, we previously consulted the real FS instead of the provided underlying VFS. This PR fixes that issue.

---

Full diff: https://github.com/llvm/llvm-project/pull/160942.diff

2 Files Affected:

• (modified) llvm/lib/Support/VirtualFileSystem.cpp (+1-1)
• (modified) llvm/unittests/Support/VirtualFileSystemTest.cpp (+30-1)

diff --git a/llvm/lib/Support/VirtualFileSystem.cpp b/llvm/lib/Support/VirtualFileSystem.cpp
index cf784595c2f1c..7ff62d43ba205 100644
--- a/llvm/lib/Support/VirtualFileSystem.cpp
+++ b/llvm/lib/Support/VirtualFileSystem.cpp
@@ -1973,7 +1973,7 @@ class llvm::vfs::RedirectingFileSystemParser {
           EC = FS->makeAbsolute(FullPath, Name);
           Name = canonicalize(Name);
         } else {
-          EC = sys::fs::make_absolute(Name);
+          EC = FS->makeAbsolute(Name);
         }
         if (EC) {
           assert(NameValueNode && "Name presence should be checked earlier");
diff --git a/llvm/unittests/Support/VirtualFileSystemTest.cpp b/llvm/unittests/Support/VirtualFileSystemTest.cpp
index 6228de8aa897a..e6c75a60a6a80 100644
--- a/llvm/unittests/Support/VirtualFileSystemTest.cpp
+++ b/llvm/unittests/Support/VirtualFileSystemTest.cpp
@@ -1941,7 +1941,7 @@ TEST_F(VFSFromYAMLTest, ReturnsExternalPathVFSHit) {
   EXPECT_EQ(0, NumDiagnostics);
 }
 
-TEST_F(VFSFromYAMLTest, RootRelativeTest) {
+TEST_F(VFSFromYAMLTest, RootRelativeToOverlayDirTest) {
   auto Lower = makeIntrusiveRefCnt<DummyFileSystem>();
   Lower->addDirectory("//root/foo/bar");
   Lower->addRegularFile("//root/foo/bar/a");
@@ -2004,6 +2004,35 @@ TEST_F(VFSFromYAMLTest, RootRelativeTest) {
 #endif
 }
 
+TEST_F(VFSFromYAMLTest, RootRelativeToCWDTest) {
+  auto Lower = makeIntrusiveRefCnt<DummyFileSystem>();
+  Lower->addDirectory("//root/foo/bar");
+  Lower->addRegularFile("//root/foo/bar/a");
+  Lower->addDirectory("//root/foo/bar/cwd");
+  Lower->addRegularFile("//root/foo/bar/cwd/a");
+  Lower->setCurrentWorkingDirectory("//root/foo/bar/cwd");
+  IntrusiveRefCntPtr<vfs::FileSystem> FS =
+      getFromYAMLString("{\n"
+                        "  'case-sensitive': false,\n"
+                        "  'root-relative': 'cwd',\n"
+                        "  'roots': [\n"
+                        "    { 'name': 'b', 'type': 'file',\n"
+                        "      'external-contents': '//root/foo/bar/a'\n"
+                        "    }\n"
+                        "  ]\n"
+                        "}",
+                        Lower, "//root/foo/bar/overlay");
+
+  ASSERT_NE(FS.get(), nullptr);
+
+  ErrorOr<vfs::Status> S1 = FS->status("//root/foo/bar/b");
+  ASSERT_TRUE(S1.getError());
+
+  ErrorOr<vfs::Status> S2 = FS->status("//root/foo/bar/cwd/b");
+  ASSERT_FALSE(S2.getError());
+  EXPECT_EQ("//root/foo/bar/a", S2->getName());
+}
+
 TEST_F(VFSFromYAMLTest, ReturnsInternalPathVFSHit) {
   auto BaseFS = makeIntrusiveRefCnt<vfs::InMemoryFileSystem>();
   BaseFS->addFile("//root/foo/realname", 0,