Use a depfile to know when to regenerate notice files

android_webview/tools/webview_licenses.py

Index: android_webview/tools/webview_licenses.py
diff --git a/android_webview/tools/webview_licenses.py b/android_webview/tools/webview_licenses.py
index f747cb8a36f8559aac39b46695e28bb48c9f20e8..0e5d37c551cdccbd3888d2206d4392cd2651e710 100755
--- a/android_webview/tools/webview_licenses.py
+++ b/android_webview/tools/webview_licenses.py
@@ -36,6 +36,8 @@ third_party = \
   imp.load_source('PRESUBMIT', \
                   os.path.join(REPOSITORY_ROOT, 'third_party', 'PRESUBMIT.py'))
 
+sys.path.append(os.path.join(REPOSITORY_ROOT, 'build/android/gyp/util'))
+import build_utils
 sys.path.append(os.path.join(REPOSITORY_ROOT, 'third_party'))
 import jinja2
 sys.path.append(os.path.join(REPOSITORY_ROOT, 'tools'))
@@ -170,15 +172,9 @@ def _Scan():
 
 class TemplateEntryGenerator(object):
   def __init__(self):
-    self._generate_licenses_file_list_only = False
     self._toc_index = 0
 
-  def SetGenerateLicensesFileListOnly(self, generate_licenses_file_list_only):
-    self._generate_licenses_file_list_only = generate_licenses_file_list_only
-
   def _ReadFileGuessEncoding(self, name):
-    if self._generate_licenses_file_list_only:
-      return ''
     contents = ''
     with open(name, 'rb') as input_file:
       contents = input_file.read()
@@ -200,15 +196,13 @@ class TemplateEntryGenerator(object):
     }
 
 
-def GenerateNoticeFile(generate_licenses_file_list_only=False):
+def GenerateNoticeFile():
   """Generates the contents of an Android NOTICE file for the third-party code.
   This is used by the snapshot tool.
   Returns:
-    The contents of the NOTICE file.
+    A tuple of (input paths, contents of the NOTICE file).
   """
-
   generator = TemplateEntryGenerator()
-  generator.SetGenerateLicensesFileListOnly(generate_licenses_file_list_only)
   # Start from Chromium's LICENSE file
   entries = [generator.MetadataToTemplateEntry({
     'Name': 'The Chromium Project',
@@ -234,14 +228,16 @@ def GenerateNoticeFile(generate_licenses_file_list_only=False):
     if license_file and license_file != licenses.NOT_SHIPPED:
       entries.append(generator.MetadataToTemplateEntry(metadata))
 
-  if generate_licenses_file_list_only:
-    return [entry['license_file'] for entry in entries]
-  else:
-    env = jinja2.Environment(
-      loader=jinja2.FileSystemLoader(os.path.dirname(__file__)),
-      extensions=['jinja2.ext.autoescape'])
-    template = env.get_template('licenses_notice.tmpl')
-    return template.render({ 'entries': entries }).encode('utf8')
+  entries.sort(key=lambda entry: entry['name'])
+
+  license_file_list = sorted(set([entry['license_file'] for entry in entries]))
+  license_file_list = [os.path.relpath(p) for p in license_file_list]
+  env = jinja2.Environment(
+    loader=jinja2.FileSystemLoader(os.path.dirname(__file__)),
+    extensions=['jinja2.ext.autoescape'])
+  template = env.get_template('licenses_notice.tmpl')
+  notice_file_contents = template.render({'entries': entries}).encode('utf8')
+  return (license_file_list, notice_file_contents)
 
 
 def main():
@@ -254,16 +250,16 @@ def main():
   parser = optparse.OptionParser(formatter=FormatterWithNewLines(),
                                  usage='%prog [options]')
   parser.add_option('--json', help='Path to JSON output file')
+  build_utils.AddDepfileOption(parser)
   parser.description = (__doc__ +
                         '\nCommands:\n'
                         '  scan Check licenses.\n'
-                        '  notice_deps Generate the list of dependencies for '
                         'Android NOTICE file.\n'
                         '  notice [file] Generate Android NOTICE file on '
                         'stdout or into |file|.\n'
                         '  display_copyrights Display autorship on the files'
                         ' using names provided via stdin.\n')
-  (options, args) = parser.parse_args()
+  options, args = parser.parse_args()
   if len(args) < 1:
     parser.print_help()
     return ScanResult.Errors
@@ -276,25 +272,23 @@ def main():
       with open(options.json, 'w') as f:
         json.dump(problem_paths, f)
     return scan_result
-  elif args[0] == 'notice_deps':
-    # 'set' is used to eliminate duplicate references to the same license file.
-    print ' '.join(
-      sorted(set(GenerateNoticeFile(generate_licenses_file_list_only=True))))
-    return ScanResult.Ok
-  elif args[0] == 'gn_notice_deps':
-    # generate list for gn.
-    # 'set' is used to eliminate duplicate references to the same license file.
-    gn_file_list = ['"' + f + '"' for f in
-        sorted(set(GenerateNoticeFile(generate_licenses_file_list_only=True)))]
-    print '[%s] ' % ','.join(gn_file_list)
-    return ScanResult.Ok
   elif args[0] == 'notice':
-    notice_file_contents = GenerateNoticeFile()
+    license_file_list, notice_file_contents = GenerateNoticeFile()
     if len(args) == 1:
       print notice_file_contents
     else:
       with open(args[1], 'w') as output_file:
         output_file.write(notice_file_contents)
+    if options.depfile:
+      assert args[1]
+      # 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.
+      build_utils.WriteDepfile(options.depfile, args[1],
+                               license_file_list + ['build.ninja'])
+

[Dirk Pranke, 2017/02/10 00:15:59]

I don't understand this block. Why do you want to re-run this whenever `gn gen`
is run? What are you worried about becoming out of date? 

[agrieve, 2017/02/10 00:32:35]

Before this change, it was scanning the filesystem during "gn gen", and that
would cause it to tell ninja of any new LICENSE files that popped up.

With this change, it's not scanning during gn gen, so any new third_party
subdirectories that get pulled in will not be noticed by incremental builds. So,
the assumption here is that a new third_party library being added will result in
a "gn gen", which will in turn tell the license scraper to re-scan.

     return ScanResult.Ok
   elif args[0] == 'display_copyrights':
     files = sys.stdin.read().splitlines()