Python script to find unused image assets in .grd files

This script searches for unused art assets listed in a .grd file. It uses
git grep to look for references to the IDR resource id or the base filename.
If neither is found, the file is reported unused.

BUG=280719
TEST=manually run on ash_resources.grd
R=oshima@chromium.org, skuhne@chromium.org

Review URL: https://codereview.chromium.org/23694005

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@220368 0039d316-1c4b-4281-b951-d872f2087c98

1 files changed, 194 insertions, 0 deletions

diff --git a/tools/resources/find_unused_resources.py b/tools/resources/find_unused_resources.py
new file mode 100755
index 0000000..87bae4b
--- /dev/null
+++ b/tools/resources/find_unused_resources.py
@@ -0,0 +1,194 @@
+#!/usr/bin/env python
+# Copyright 2013 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.
+
+"""This script searches for unused art assets listed in a .grd file.
+
+It uses git grep to look for references to the IDR resource id or the base
+filename. If neither is found, the file is reported unused.
+
+Requires a git checkout. Must be run from your checkout's "src" root.
+
+Example:
+  cd /work/chrome/src
+  tools/resources/find_unused_resouces.py ash/resources/ash_resources.grd
+"""
+
+__author__ = 'jamescook@chromium.org (James Cook)'
+
+
+import os
+import re
+import subprocess
+import sys
+
+
+def GetBaseResourceId(resource_id):
+  """Removes common suffixes from a resource ID.
+
+  Removes suffixies that may be added by macros like IMAGE_GRID or IMAGE_BORDER.
+  For example, converts IDR_FOO_LEFT and IDR_FOO_RIGHT to just IDR_FOO.
+
+  Args:
+    resource_id: String resource ID.
+
+  Returns:
+    A string with the base part of the resource ID.
+  """
+  suffixes = [
+      '_TOP_LEFT', '_TOP', '_TOP_RIGHT',
+      '_LEFT', '_MIDDLE', '_RIGHT',
+      '_BOTTOM_LEFT', '_BOTTOM', '_BOTTOM_RIGHT',
+      '_TL', '_T', '_TR',
+      '_L', '_M', '_R',
+      '_BL', '_B', '_BR']
+  # Note: This does not check _HOVER, _PRESSED, _HOT, etc. as those are never
+  # used in macros.
+  for suffix in suffixes:
+    if resource_id.endswith(suffix):
+      resource_id = resource_id[:-len(suffix)]
+  return resource_id
+
+
+def FindFilesWithContents(string_a, string_b):
+  """Returns list of paths of files that contain |string_a| or |string_b|.
+
+  Uses --name-only to print the file paths. The default behavior of git grep
+  is to OR together multiple patterns.
+
+  Args:
+    string_a: A string to search for (not a regular expression).
+    string_b: As above.
+
+  Returns:
+    A list of file paths as strings.
+  """
+  matching_files = subprocess.check_output([
+      'git', 'grep', '--name-only', '--fixed-strings', '-e', string_a,
+      '-e', string_b])
+  files_list = matching_files.split('\n')
+  # The output ends in a newline, so slice that off.
+  files_list = files_list[:-1]
+  return files_list
+
+
+def GetUnusedResources(grd_filepath):
+  """Returns a list of resources that are unused in the code.
+
+  Prints status lines to the console because this function is quite slow.
+
+  Args:
+    grd_filepath: Path to a .grd file listing resources.
+
+  Returns:
+    A list of pairs of [resource_id, filepath] for the unused resources.
+  """
+  unused_resources = []
+  grd_file = open(grd_filepath, 'r')
+  grd_data = grd_file.read()
+  print 'Checking:'
+  # Match the resource id and file path out of substrings like:
+  # ...name="IDR_FOO_123" file="common/foo.png"...
+  # by matching between the quotation marks.
+  pattern = re.compile(
+      r"""name="([^"]*)"  # Match resource ID between quotes.
+      \s*                 # Run of whitespace, including newlines.
+      file="([^"]*)"      # Match file path between quotes.""",
+      re.VERBOSE)
+  # Use finditer over the file contents because there may be newlines between
+  # the name and file attributes.
+  for result in pattern.finditer(grd_data):
+    # Extract the IDR resource id and file path.
+    resource_id = result.group(1)
+    filepath = result.group(2)
+    filename = os.path.basename(filepath)
+    # Print progress as we go along.
+    print resource_id
+    # Ensure the resource isn't used anywhere by checking both for the resource
+    # id (which should appear in C++ code) and the raw filename (in case the
+    # file is referenced in a script, test HTML file, etc.).
+    base_resource_id = GetBaseResourceId(resource_id)
+    matching_files = FindFilesWithContents(base_resource_id, filename)
+    # Each file is matched once in the resource file itself. If there are no
+    # other matching files, it is unused.
+    if len(matching_files) == 1:
+      # Give the user some happy news.
+      print 'Unused!'
+      unused_resources.append([resource_id, filepath])
+
+  return unused_resources
+
+
+def GetScaleDirectories(resources_path):
+  """Returns a list of paths to per-scale-factor resource directories.
+
+  Assumes the directory names end in '_percent', for example,
+  ash/resources/default_200_percent or
+  chrome/app/theme/resources/touch_140_percent
+
+  Args:
+    resources_path: The base path of interest.
+
+  Returns:
+    A list of paths relative to the 'src' directory.
+  """
+  file_list = os.listdir(resources_path)
+  scale_directories = []
+  for file_entry in file_list:
+    file_path = os.path.join(resources_path, file_entry)
+    if os.path.isdir(file_path) and file_path.endswith('_percent'):
+      scale_directories.append(file_path)
+
+  scale_directories.sort()
+  return scale_directories
+
+
+def main():
+  # The script requires exactly one parameter, the .grd file path.
+  if len(sys.argv) != 2:
+    print 'Usage: tools/resources/find_unused_resources.py <path/to/grd>'
+    sys.exit(1)
+  grd_filepath = sys.argv[1]
+
+  # Try to ensure we are in a source checkout.
+  current_dir = os.getcwd()
+  if os.path.basename(current_dir) != 'src':
+    print 'Script must be run in your "src" directory.'
+    sys.exit(1)
+
+  # We require a git checkout to use git grep.
+  if not os.path.exists(current_dir + '/.git'):
+    print 'You must use a git checkout for this script to run.'
+    print current_dir + '/.git', 'not found.'
+    sys.exit(1)
+
+  # Look up the scale-factor directories.
+  resources_path = os.path.dirname(grd_filepath)
+  scale_directories = GetScaleDirectories(resources_path)
+  if not scale_directories:
+    print 'No scale directories (like "default_100_percent") found.'
+    sys.exit(1)
+
+  # |unused_resources| stores pairs of [resource_id, filepath] for resource ids
+  # that are not referenced in the code.
+  unused_resources = GetUnusedResources(grd_filepath)
+  if not unused_resources:
+    print 'All resources are used.'
+    sys.exit(0)
+
+  # Dump our output for the user.
+  print
+  print 'Unused resource ids:'
+  for resource_id, filepath in unused_resources:
+    print resource_id
+  # Print a list of 'git rm' command lines to remove unused assets.
+  print
+  print 'Unused files:'
+  for resource_id, filepath in unused_resources:
+    for directory in scale_directories:
+      print 'git rm ' + os.path.join(directory, filepath)
+
+
+if __name__ == '__main__':
+  main()