GN: Don't write stamp files for one rule.

tools/gn/ninja_target_writer_unittest.cc

 // Copyright 2014 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 <sstream>
 
 #include "testing/gtest/include/gtest/gtest.h"
 #include "tools/gn/ninja_target_writer.h"
 #include "tools/gn/target.h"
 #include "tools/gn/test_with_scope.h"
@@ skipping 54 matching lines @@
   ASSERT_TRUE(target.OnResolved(&err));
   ASSERT_TRUE(action.OnResolved(&err));
 
   // Input deps for the base (should be only the script itself).
   {
     std::ostringstream stream;
     TestingNinjaTargetWriter writer(&base_target, setup.toolchain(), stream);
     OutputFile dep =
         writer.WriteInputDepsStampAndGetDep(std::vector<const Target*>());
 
-    EXPECT_EQ("obj/foo/base.inputdeps.stamp", dep.value());
-    EXPECT_EQ("build obj/foo/base.inputdeps.stamp: stamp "
-                  "../../foo/script.py\n",
-              stream.str());
+    // Since there is only one dependency, it should just be returned and
+    // nothing written to the stream.
+    EXPECT_EQ("../../foo/script.py", dep.value());
+    EXPECT_EQ("", stream.str());
   }
 
   // Input deps for the target (should depend on the base).
   {
     std::ostringstream stream;
     TestingNinjaTargetWriter writer(&target, setup.toolchain(), stream);
     OutputFile dep =
         writer.WriteInputDepsStampAndGetDep(std::vector<const Target*>());
 
+    // Since there is more than one dependency, a stamp file will be returned
+    // and the rule for the stamp file will be written to the stream.
     EXPECT_EQ("obj/foo/target.inputdeps.stamp", dep.value());
     EXPECT_EQ("build obj/foo/target.inputdeps.stamp: stamp "
                   "../../foo/input.txt obj/foo/base.stamp\n",
               stream.str());
   }
 
   // Input deps for action which should depend on the base since its a hard dep
   // that is a (indirect) dependency, as well as the the action source.
   {
     std::ostringstream stream;
@@ skipping 28 matching lines @@
   Target target(setup.settings(), Label(SourceDir("//foo/"), "target"));
   target.set_output_type(Target::EXECUTABLE);
   target.SetToolchain(setup.toolchain());
   ASSERT_TRUE(target.OnResolved(&err));
 
   std::ostringstream stream;
   TestingNinjaTargetWriter writer(&target, setup.toolchain(), stream);
   OutputFile dep =
       writer.WriteInputDepsStampAndGetDep(std::vector<const Target*>());
 
-  EXPECT_EQ("obj/foo/target.inputdeps.stamp", dep.value());
-  EXPECT_EQ("build obj/foo/target.inputdeps.stamp: stamp "
-                "obj/foo/setup.stamp\n",
-            stream.str());
+  // Since there is more than one dependency, a stamp file will be returned
+  // and the rule for the stamp file will be written to the stream.
+  EXPECT_EQ("obj/foo/setup.stamp", dep.value());
+  EXPECT_EQ("", stream.str());
 }