Fix GN action target writing with no sources list.

tools/gn/ninja_action_target_writer_unittest.cc

 // Copyright (c) 2013 The Chromium 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 <algorithm>
 #include <sstream>
 
 #include "testing/gtest/include/gtest/gtest.h"
 #include "tools/gn/ninja_action_target_writer.h"
 #include "tools/gn/substitution_list.h"
@@ skipping 10 matching lines @@
   std::ostringstream out;
   NinjaActionTargetWriter writer(&target, setup.toolchain(), out);
 
   SourceFile source("//foo/bar.in");
   std::vector<OutputFile> output_files;
   writer.WriteOutputFilesForBuildLine(source, &output_files);
 
   EXPECT_EQ(" gen/a$ bbar.h gen/bar.cc", out.str());
 }
 
+// Tests an action with no sources.
+TEST(NinjaActionTargetWriter, ActionNoSources) {
+  TestWithScope setup;
+  setup.build_settings()->SetBuildDir(SourceDir("//out/Debug/"));
+  Target target(setup.settings(), Label(SourceDir("//foo/"), "bar"));
+  target.set_output_type(Target::ACTION);
+
+  target.action_values().set_script(SourceFile("//foo/script.py"));
+  target.inputs().push_back(SourceFile("//foo/included.txt"));
+
+  target.action_values().outputs() =
+      SubstitutionList::MakeForTest("//out/Debug/foo.out");
+
+  setup.settings()->set_target_os(Settings::LINUX);
+  setup.build_settings()->set_python_path(base::FilePath(FILE_PATH_LITERAL(
+      "/usr/bin/python")));
+
+  std::ostringstream out;
+  NinjaActionTargetWriter writer(&target, setup.toolchain(), out);
+  writer.Run();
+
+  const char expected[] =
+      "rule __foo_bar___rule\n"
+      "  command = /usr/bin/python ../../foo/script.py\n"
+      "  description = ACTION //foo:bar()\n"
+      "  restat = 1\n"
+      "build obj/foo/bar.inputdeps.stamp: stamp ../../foo/script.py "
+          "../../foo/included.txt\n"
+      "\n"
+      "build foo.out: __foo_bar___rule | obj/foo/bar.inputdeps.stamp\n"
+      "\n"
+      "build obj/foo/bar.stamp: stamp foo.out\n";
+  EXPECT_EQ(expected, out.str());
+}
+
 // Makes sure that we write sources as input dependencies for actions with
 // both sources and inputs (ACTION_FOREACH treats the sources differently).
 TEST(NinjaActionTargetWriter, ActionWithSources) {
   TestWithScope setup;
   setup.build_settings()->SetBuildDir(SourceDir("//out/Debug/"));
   Target target(setup.settings(), Label(SourceDir("//foo/"), "bar"));
   target.set_output_type(Target::ACTION);
 
   target.action_values().set_script(SourceFile("//foo/script.py"));
 
@@ skipping 266 matching lines @@
         "build input2.out: __foo_bar___rule ../../foo/input2.txt"
             " | obj/foo/bar.inputdeps.stamp\n"
         "  unique_name = 1\n"
         "  source_name_part = input2\n"
         "  depfile = gen/input2.d\n"
         "\n"
         "build obj/foo/bar.stamp: stamp input1.out input2.out\n";
     EXPECT_EQ(expected_win, out.str());
   }
 }