Add the ability to generate a depfile when running grit build.

grit/tool/build_unittest.py

 #!/usr/bin/env python
 # Copyright (c) 2012 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.
 
 '''Unit tests for the 'grit build' tool.
 '''
 
 import os
 import sys
@@ skipping 15 matching lines @@
     # another <message>.
     output_dir = tempfile.mkdtemp()
     builder = build.RcBuilder()
     class DummyOpts(object):
       def __init__(self):
         self.input = util.PathFromRoot('grit/testdata/substitute.grd')
         self.verbose = False
         self.extra_verbose = False
     builder.Run(DummyOpts(), ['-o', output_dir])
 
+  def testGenerateDepFile(self):
+    output_dir = tempfile.mkdtemp()
+    builder = build.RcBuilder()
+    class DummyOpts(object):
+      def __init__(self):
+        self.input = util.PathFromRoot('grit/testdata/substitute.grd')
+        self.verbose = False
+        self.extra_verbose = False
+    builder.Run(DummyOpts(), ['-o', output_dir, '--dep-dir', output_dir])
+
+    expected_dep_file = os.path.join(output_dir, 'substitute.grd.d')
+    self.failUnless(os.path.isfile(expected_dep_file))
+    with open(expected_dep_file) as f:
+      line = f.readline()
+      (dep_file_name, deps_string) = line.split(': ')
+      deps = deps_string.split(' ')
+      self.failUnlessEqual(os.path.abspath(expected_dep_file),
+          os.path.abspath(os.path.join(output_dir, dep_file_name)),
+          "depfile should refer to itself as the depended upon file")
+      self.failUnlessEqual(1, len(deps))
+      self.failUnlessEqual(deps[0],
+          util.PathFromRoot('grit/testdata/substitute.xmb'))
+
 
 if __name__ == '__main__':
   unittest.main()