Make fml::ScopedCleanupClosure std::move-able and add unit tests. (#45772)

Fixes flutter/flutter#134568.

Author: matanlurey

ci/licenses_golden/excluded_files

@@ -83,6 +83,7 @@
 ../../../flutter/fml/ascii_trie_unittests.cc
 ../../../flutter/fml/backtrace_unittests.cc
 ../../../flutter/fml/base32_unittest.cc
+../../../flutter/fml/closure_unittests.cc
 ../../../flutter/fml/command_line_unittest.cc
 ../../../flutter/fml/container_unittests.cc
 ../../../flutter/fml/endianness_unittests.cc

fml/BUILD.gn

@@ -319,6 +319,7 @@ if (enable_unittests) {
       "ascii_trie_unittests.cc",
       "backtrace_unittests.cc",
       "base32_unittest.cc",
+      "closure_unittests.cc",
       "command_line_unittest.cc",
       "container_unittests.cc",
       "endianness_unittests.cc",

fml/closure.h

@@ -29,10 +29,19 @@ using closure = std::function<void()>;
 ///             automatically at the end of the scope. This covers the cases
 ///             where there are early returns as well.
 ///
-class ScopedCleanupClosure {
+class ScopedCleanupClosure final {
  public:
   ScopedCleanupClosure() = default;
 
+  ScopedCleanupClosure(ScopedCleanupClosure&& other) {
+    closure_ = other.Release();
+  }
+
+  ScopedCleanupClosure& operator=(ScopedCleanupClosure&& other) {
+    closure_ = other.Release();
+    return *this;
+  }
+
   explicit ScopedCleanupClosure(const fml::closure& closure)
       : closure_(closure) {}
 

fml/closure_unittests.cc

@@ -0,0 +1,71 @@
+// Copyright 2013 The Flutter Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "fml/closure.h"
+#include "gtest/gtest.h"
+
+TEST(ScopedCleanupClosureTest, DestructorDoesNothingWhenNoClosureSet) {
+  fml::ScopedCleanupClosure cleanup;
+
+  // Nothing should happen.
+}
+
+TEST(ScopedCleanupClosureTest, ReleaseDoesNothingWhenNoClosureSet) {
+  fml::ScopedCleanupClosure cleanup;
+
+  // Nothing should happen.
+  EXPECT_EQ(nullptr, cleanup.Release());
+}
+
+TEST(ScopedCleanupClosureTest, ClosureInvokedOnDestructorWhenSetInConstructor) {
+  auto invoked = false;
+
+  {
+    fml::ScopedCleanupClosure cleanup([&invoked]() { invoked = true; });
+
+    EXPECT_FALSE(invoked);
+  }
+
+  EXPECT_TRUE(invoked);
+}
+
+TEST(ScopedCleanupClosureTest, ClosureInvokedOnDestructorWhenSet) {
+  auto invoked = false;
+
+  {
+    fml::ScopedCleanupClosure cleanup;
+    cleanup.SetClosure([&invoked]() { invoked = true; });
+
+    EXPECT_FALSE(invoked);
+  }
+
+  EXPECT_TRUE(invoked);
+}
+
+TEST(ScopedCleanupClosureTest, ClosureNotInvokedWhenMoved) {
+  auto invoked = 0;
+
+  {
+    fml::ScopedCleanupClosure cleanup([&invoked]() { invoked++; });
+    fml::ScopedCleanupClosure cleanup2(std::move(cleanup));
+
+    EXPECT_EQ(0, invoked);
+  }
+
+  EXPECT_EQ(1, invoked);
+}
+
+TEST(ScopedCleanupClosureTest, ClosureNotInvokedWhenMovedViaAssignment) {
+  auto invoked = 0;
+
+  {
+    fml::ScopedCleanupClosure cleanup([&invoked]() { invoked++; });
+    fml::ScopedCleanupClosure cleanup2;
+    cleanup2 = std::move(cleanup);
+
+    EXPECT_EQ(0, invoked);
+  }
+
+  EXPECT_EQ(1, invoked);
+}