Polymer: Update find_unused_elements.py

third_party/polymer/v1_0/find_unused_elements.py

 # Copyright 2016 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.
 
 """Identifies Polymer elements that downloaded but not used by Chrome.
 
 Only finds "first-order" unused elements; re-run after removing unused elements
 to check if other elements have become unused.
 """
 
 import os
 import re
 import subprocess
+import sys
+import tempfile
 
+_HERE_PATH = os.path.dirname(__file__)
+_SRC_PATH = os.path.normpath(os.path.join(_HERE_PATH, '..', '..', '..'))
+sys.path.append(os.path.join(_SRC_PATH, 'third_party', 'node'))

[michaelpg, 2017/06/05 19:22:36]

remove uglify check in reproduce.sh

[dpapad, 2017/06/05 19:42:02]

Done.

+import node
+import node_modules
 
 class UnusedElementsDetector(object):
   """Finds unused Polymer elements."""
 
   # Unused elements to ignore because we plan to use them soon.
   __WHITELIST = (
     # Necessary for closure.
     'polymer-externs',
   )
 
@@ skipping 26 matching lines @@
 
     Returns:
       A string consisting of the minified file contents with comments and grit
       directives removed.
     """
     with open(filename) as f:
       text = f.read()
     text = re.sub('<if .*?>', '', text, flags=re.IGNORECASE)
     text = re.sub('</if>', '', text, flags=re.IGNORECASE)
 
-    proc = subprocess.Popen(['uglifyjs', filename], stdout=subprocess.PIPE)

[Dan Beam, 2017/06/02 21:49:08]

can we change to subprocess2 and use stderr=subprocess.VOID instead?

https://cs.chromium.org/chromium/build/tests/masters_util.py?type=cs&q=stderr...

[dpapad, 2017/06/05 19:22:09]

We probably could (have not tried yet), but importing subproccess2 is a bit
involved, see lines
https://cs.chromium.org/chromium/build/tests/masters_util.py?type=cs&q=stderr....

Do you still think this is a better idea than just writing to a temp file? If
not, I might not get to it today.

[dpapad, 2017/06/06 21:39:55]

This is not necessary anymore. I rebased this CL after
https://codereview.chromium.org/2921793002 (which changes uglifyjs to
uglify-es), and there is no need to use the temporary file anymore, see patch
#4.

-    return proc.stdout.read()
+    # Need to write the output to a temporary file to avoid
+    # https://github.com/mishoo/UglifyJS2/issues/641 which has been fixed after
+    # version 2.4.21.
+    # TODO(dpapad): Chromium currently uses 2.4.10, update to latest version.
+    with tempfile.NamedTemporaryFile(mode='wt+') as tmp:
+      node.RunNode([
+          node_modules.PathToUglifyJs(), filename, '--output', tmp.name])
+      output = tmp.read()
+
+    return output
 
   @staticmethod
   def __StripComments(filename):
     """Returns the contents of a JavaScript or HTML file with comments removed.
 
     Args:
       filename: The name of the file to read.
 
     Returns:
       A string consisting of the file contents processed via
@@ skipping 53 matching lines @@
       for (dirpath, _, filenames) in os.walk(path):
         # Ignore the element's own files.
         if dirpath.startswith(os.path.join(
             self.__COMPONENTS_DIR, element_dir)):
           continue
 
         for filename in filenames:
           if not filename.endswith('.html') and not filename.endswith('.js'):
             continue
 
-          # Skip generated files that may include the element source.
-          if filename in ('crisper.js', 'vulcanized.html',
-                          'app.crisper.js', 'app.vulcanized.html'):
-            continue
-
           with open(os.path.join(dirpath, filename)) as f:
             text = f.read()
           if not re.search('/%s/' % element_dir, text):
             continue
 
           # Check the file again, ignoring comments (e.g. example imports and
           # scripts).
           if re.search('/%s' % element_dir,
                        self.__StripComments(
                          os.path.join(dirpath, filename))):
             return True
     return False
 
 
 if __name__ == '__main__':
   UnusedElementsDetector().Run()