Use a depfile to know when to regenerate notice files

tools/licenses.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.
 
 """Utility for checking and processing licensing information in third_party
 directories.
 
 Usage: licenses.py <command>
 
 Commands:
   scan     scan third_party directories, verifying that we have licensing info
   credits  generate about:credits on stdout
 
 (You can also import this as a module.)
 """
 
 import argparse
 import cgi
 import os
 import sys
 
+# TODO(agrieve): Move build_utils.WriteDepFile into a non-android directory.
+_REPOSITORY_ROOT = os.path.dirname(os.path.dirname(__file__))
+sys.path.append(os.path.join(_REPOSITORY_ROOT, 'build/android/gyp/util'))
+import build_utils
+
+
 # Paths from the root of the tree to directories to skip.
 PRUNE_PATHS = set([
     # Placeholder directory only, not third-party code.
     os.path.join('third_party','adobe'),
 
     # Already covered by //third_party/android_tools.
     os.path.join('third_party','android_tools_internal'),
 
     # Apache 2.0 license. See crbug.com/140478
     os.path.join('third_party','bidichecker'),
@@ skipping 436 matching lines @@
             errors.append((path, e.args[0]))
             continue
 
     for path, error in sorted(errors):
         print path + ": " + error
 
     return len(errors) == 0
 
 
 def GenerateCredits(
-        file_template_file, entry_template_file, output_file, target_os):
+        file_template_file, entry_template_file, output_file, target_os,
+        depfile=None):
     """Generate about:credits."""
 
     def EvaluateTemplate(template, env, escape=True):
         """Expand a template with variables like {{foo}} using a
         dictionary of expansions."""
         for key, val in env.items():
             if escape:
                 val = cgi.escape(val)
             template = template.replace('{{%s}}' % key, val)
         return template
 
-    root = os.path.join(os.path.dirname(__file__), '..')
-    third_party_dirs = FindThirdPartyDirs(PRUNE_PATHS, root)
+    third_party_dirs = FindThirdPartyDirs(PRUNE_PATHS, _REPOSITORY_ROOT)
 
     if not file_template_file:
-        file_template_file = os.path.join(root, 'components', 'about_ui',
-                                          'resources', 'about_credits.tmpl')
+        file_template_file = os.path.join(_REPOSITORY_ROOT, 'components',
+                                          'about_ui', 'resources',
+                                          'about_credits.tmpl')
     if not entry_template_file:
-        entry_template_file = os.path.join(root, 'components', 'about_ui',
-                                           'resources',
+        entry_template_file = os.path.join(_REPOSITORY_ROOT, 'components',
+                                           'about_ui', 'resources',
                                            'about_credits_entry.tmpl')
 
     entry_template = open(entry_template_file).read()
     entries = []
     for path in third_party_dirs:
         try:
-            metadata = ParseDir(path, root)
+            metadata = ParseDir(path, _REPOSITORY_ROOT)
         except LicenseError:
             # TODO(phajdan.jr): Convert to fatal error (http://crbug.com/39240).
             continue
         if metadata['License File'] == NOT_SHIPPED:
             continue
         if target_os == 'ios':
             # Skip over files that are known not to be used on iOS.
             if path in KNOWN_NON_IOS_LIBRARIES:
                 continue
         env = {
             'name': metadata['Name'],
             'url': metadata['URL'],
             'license': open(metadata['License File'], 'rb').read(),
         }
         entry = {
             'name': metadata['Name'],
             'content': EvaluateTemplate(entry_template, env),
+            'license_file': metadata['License File'],
         }
         entries.append(entry)
 
     entries.sort(key=lambda entry: (entry['name'], entry['content']))
     entries_contents = '\n'.join([entry['content'] for entry in entries])
     file_template = open(file_template_file).read()
     template_contents = "<!-- Generated by licenses.py; do not edit. -->"
     template_contents += EvaluateTemplate(file_template,
                                           {'entries': entries_contents},
                                           escape=False)
 
     if output_file:
       with open(output_file, 'w') as output:
         output.write(template_contents)
     else:
       print template_contents
 
+    if depfile:
+      assert output_file
+      # Add in build.ninja so that the target will be considered dirty whenever
+      # gn gen is run. Otherwise, it will fail to notice new files being added.
+      # This is still no perfect, as it will fail if no build files are changed,
+      # but a new README.chromium / LICENSE is added. This shouldn't happen in
+      # practice however.
+      license_file_list = (entry['license_file'] for entry in entries)
+      license_file_list = (os.path.relpath(p) for p in license_file_list)
+      license_file_list = sorted(set(license_file_list))
+      build_utils.WriteDepfile(depfile, output_file,
+                               license_file_list + ['build.ninja'])
+
     return True
 
 
 def main():
     parser = argparse.ArgumentParser()
     parser.add_argument('--file-template',
                         help='Template HTML to use for the license page.')
     parser.add_argument('--entry-template',
                         help='Template HTML to use for each license.')
     parser.add_argument('--target-os',
                         help='OS that this build is targeting.')
     parser.add_argument('command', choices=['help', 'scan', 'credits'])
     parser.add_argument('output_file', nargs='?')
+    build_utils.AddDepfileOption(parser)
     args = parser.parse_args()
 
     if args.command == 'scan':
         if not ScanThirdPartyDirs():
             return 1
     elif args.command == 'credits':
         if not GenerateCredits(args.file_template, args.entry_template,
-                               args.output_file, args.target_os):
+                               args.output_file, args.target_os, args.depfile):
             return 1
     else:
         print __doc__
         return 1
 
 
 if __name__ == '__main__':
   sys.exit(main())