Bazel client: simplify ReadDirectorySymlink

This is a bugfixed version of
https://cr.bazel.build/9520 which broke some
Google-internal tests.

This change allows removing duplicate code:
ReadDirectorySymlink was implemented on Windows as
a junction resolver, which is also implemented in
file_windows.cc. Now it uses the JunctionResolver.

RELNOTES: none

PiperOrigin-RevId: 151691895

3 files changed, 32 insertions, 0 deletions

diff --git a/src/main/cpp/util/file_platform.h b/src/main/cpp/util/file_platform.h
index 50b75de3bb..31a0d1c24c 100644
--- a/src/main/cpp/util/file_platform.h
+++ b/src/main/cpp/util/file_platform.h
@@ -130,6 +130,11 @@ enum RenameDirectoryResult {
 // Returns one of the RenameDirectoryResult enum values.
 int RenameDirectory(const std::string &old_name, const std::string &new_name);
 
+// Reads which directory a symlink points to. Puts the target of the symlink
+// in ``result`` and returns if the operation was successful. Will not work on
+// symlinks that don't point to directories on Windows.
+bool ReadDirectorySymlink(const std::string &symlink, std::string *result);
+
 // Unlinks the file given by 'file_path'.
 // Returns true on success. In case of failure sets errno.
 bool UnlinkPath(const std::string &file_path);
diff --git a/src/main/cpp/util/file_posix.cc b/src/main/cpp/util/file_posix.cc
index 076bff2bfd..daa465af94 100644
--- a/src/main/cpp/util/file_posix.cc
+++ b/src/main/cpp/util/file_posix.cc
@@ -251,6 +251,18 @@ int RenameDirectory(const std::string &old_name, const std::string &new_name) {
   }
 }
 
+bool ReadDirectorySymlink(const string &name, string *result) {
+  char buf[PATH_MAX + 1];
+  int len = readlink(name.c_str(), buf, PATH_MAX);
+  if (len < 0) {
+    return false;
+  }
+
+  buf[len] = 0;
+  *result = buf;
+  return true;
+}
+
 bool UnlinkPath(const string &file_path) {
   return unlink(file_path.c_str()) == 0;
 }
diff --git a/src/main/cpp/util/file_windows.cc b/src/main/cpp/util/file_windows.cc
index c2e0fd79ee..af6ed4f325 100644
--- a/src/main/cpp/util/file_windows.cc
+++ b/src/main/cpp/util/file_windows.cc
@@ -863,6 +863,21 @@ bool JunctionResolver::Resolve(const WCHAR* path, unique_ptr<WCHAR[]>* result) {
   return Resolve(path, result, kMaximumJunctionDepth);
 }
 
+bool ReadDirectorySymlink(const string& name, string* result) {
+  wstring wname;
+  if (!AsWindowsPathWithUncPrefix(name, &wname)) {
+    PrintError("ReadDirectorySymlink: AsWindowsPathWithUncPrefix(%s)",
+               name.c_str());
+    return false;
+  }
+  unique_ptr<WCHAR[]> result_ptr;
+  if (!JunctionResolver().Resolve(wname.c_str(), &result_ptr)) {
+    return false;
+  }
+  *result = WstringToCstring(RemoveUncPrefixMaybe(result_ptr.get())).get();
+  return true;
+}
+
 bool PathExists(const string& path) {
   if (path.empty()) {
     return false;