Partial fix for bug with creating a junction to file instead of symlink

This is a partial fix for issue bazelbuild#21747 for the `--windows_enable_symlinks` case.
The fix was suggested in discussion of this issue. This resolves the problem with creating a junction if the target path doesn't exist for those who have Windows symlinks enabled, until a complete solution is provided.

Closes bazelbuild#24051.

PiperOrigin-RevId: 688724224
Change-Id: Ie44f7834af5fd35ab57961e6012b9f336c25d606

src/main/java/com/google/devtools/build/lib/windows/WindowsFileSystem.java

@@ -79,15 +79,15 @@ protected void createSymbolicLink(PathFragment linkPath, PathFragment targetFrag
     try {
       java.nio.file.Path link = getIoFile(linkPath).toPath();
       java.nio.file.Path target = getIoFile(targetPath).toPath();
-      // Still Create a dangling junction if the target doesn't exist.
-      if (!target.toFile().exists() || target.toFile().isDirectory()) {
+      if (target.toFile().isDirectory()) {
+        WindowsFileOperations.createJunction(link.toString(), target.toString());
+      } else if (createSymbolicLinks) {
+        WindowsFileOperations.createSymlink(link.toString(), target.toString());
+      } else if (!target.toFile().exists()) {
+        // Still Create a dangling junction if the target doesn't exist.
         WindowsFileOperations.createJunction(link.toString(), target.toString());
       } else {
-        if (createSymbolicLinks) {
-          WindowsFileOperations.createSymlink(link.toString(), target.toString());
-        } else {
-          Files.copy(target, link);
-        }
+        Files.copy(target, link);
       }
     } catch (java.nio.file.FileAlreadyExistsException e) {
       throw new IOException(linkPath + ERR_FILE_EXISTS, e);

src/main/native/windows/file.cc

@@ -505,7 +505,8 @@ int CreateSymlink(const wstring& symlink_name, const wstring& symlink_target,
   const wstring target = AddUncPrefixMaybe(symlink_target);
 
   DWORD attrs = GetFileAttributesW(target.c_str());
-  if (attrs & FILE_ATTRIBUTE_DIRECTORY) {
+  if ((attrs != INVALID_FILE_ATTRIBUTES) &&
+      (attrs & FILE_ATTRIBUTE_DIRECTORY)) {
     // Instead of creating a symlink to a directory use a Junction.
     return CreateSymlinkResult::kTargetIsDirectory;
   }