Restore original override in base::ScopedPathOverride

This affects ui/base unit tests, where the test suite overrides
ui::DIR_LOCALES in its initialization function. Any ScopedPathOverride
which overrides ui::DIR_LOCALES will cause it to reset to the original
ui::DIR_LOCALES value - not the override in the test suite
initialization - which might cause order dependent tests.

Fixed: 1153235
Change-Id: I03981980a3e0c6ab2596989a2e499ec237fce206
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2563013
Commit-Queue: Michael Cui <mlcui@google.com>
Reviewed-by: danakj <danakj@chromium.org>
Cr-Commit-Position: refs/heads/master@{#833181}

base/path_service.cc

@@ -302,6 +302,16 @@ bool PathService::RemoveOverride(int key) {
   return true;
 }
 
+// static
+bool PathService::IsOverriddenForTests(int key) {
+  PathData* path_data = GetPathData();
+  DCHECK(path_data);
+
+  AutoLock scoped_lock(path_data->lock);
+
+  return path_data->overrides.find(key) != path_data->overrides.end();
+}
+
 // static
 void PathService::RegisterProvider(ProviderFunc func, int key_start,
                                    int key_end) {

base/path_service.h

@@ -86,6 +86,9 @@ class BASE_EXPORT PathService {
   // was an override to remove or false if none was present.
   // NOTE: This function is intended to be used by tests only!
   static bool RemoveOverride(int key);
+
+  // Returns whether an override is present for a special directory or file.
+  static bool IsOverriddenForTests(int key);
 };
 
 }  // namespace base

base/test/scoped_path_override.cc

@@ -10,6 +10,7 @@
 namespace base {
 
 ScopedPathOverride::ScopedPathOverride(int key) : key_(key) {
+  SaveOriginal();
   bool result = temp_dir_.CreateUniqueTempDir();
   CHECK(result);
   result = PathService::Override(key, temp_dir_.GetPath());
@@ -18,6 +19,7 @@ ScopedPathOverride::ScopedPathOverride(int key) : key_(key) {
 
 ScopedPathOverride::ScopedPathOverride(int key, const base::FilePath& dir)
     : key_(key) {
+  SaveOriginal();
   bool result = PathService::Override(key, dir);
   CHECK(result);
 }
@@ -27,14 +29,31 @@ ScopedPathOverride::ScopedPathOverride(int key,
                                        bool is_absolute,
                                        bool create)
     : key_(key) {
+  SaveOriginal();
   bool result =
       PathService::OverrideAndCreateIfNeeded(key, path, is_absolute, create);
   CHECK(result);
 }
 
+void ScopedPathOverride::SaveOriginal() {
+  if (PathService::IsOverriddenForTests(key_)) {
+    original_override_ = PathService::CheckedGet(key_);
+  }
+}
+
 ScopedPathOverride::~ScopedPathOverride() {
    bool result = PathService::RemoveOverride(key_);
    CHECK(result) << "The override seems to have been removed already!";
+   if (original_override_) {
+     // PathService::Override, by default, does some (blocking) checks to ensure
+     // that the path is absolute and exists. As the original override must have
+     // already gone through these checks, we can skip these checks here.
+     // This is needed for some tests which use ScopedPathOverride in scopes
+     // that disallow blocking.
+     result = PathService::OverrideAndCreateIfNeeded(
+         key_, *original_override_, /*is_absolute=*/true, /*create=*/false);
+     CHECK(result);
+   }
 }
 
 }  // namespace base

base/test/scoped_path_override.h

@@ -7,6 +7,7 @@
 
 #include "base/files/scoped_temp_dir.h"
 #include "base/macros.h"
+#include "base/optional.h"
 
 namespace base {
 
@@ -32,8 +33,12 @@ class ScopedPathOverride {
   ~ScopedPathOverride();
 
  private:
+  // Used for saving original_override_ when an override already exists.
+  void SaveOriginal();
+
   int key_;
   ScopedTempDir temp_dir_;
+  base::Optional<FilePath> original_override_;
 
   DISALLOW_COPY_AND_ASSIGN(ScopedPathOverride);
 };