Add a tool to fix (some) errors reported by gn gen --check.

tools/gn_check_autofix.py

Index: tools/gn_check_autofix.py
diff --git a/tools/gn_check_autofix.py b/tools/gn_check_autofix.py
new file mode 100644
index 0000000000000000000000000000000000000000..54ca1b0418621dce102bf9fa572dd87831dc6b75
--- /dev/null
+++ b/tools/gn_check_autofix.py
@@ -0,0 +1,142 @@
+#!/usr/bin/env python
+
+# Copyright (c) 2016 The WebRTC project authors. All Rights Reserved.
+#
+# Use of this source code is governed by a BSD-style license
+# that can be found in the LICENSE file in the root of the source
+# tree. An additional intellectual property rights grant can be found
+# in the file PATENTS.  All contributing project authors may
+# be found in the AUTHORS file in the root of the source tree.
+
+import os
+import re
+import shutil
+import subprocess
+import sys
+import tempfile
+
+from collections import defaultdict
+
+TARGET_RE = re.compile(
+    r'(?P<indentation_level>\s*)\w*\("(?P<target_name>\w*)"\) {$')
+
+class TemporaryDirectory(object):
+  def __init__(self):
+    self._closed = False
+    self._name = None
+    self._name = tempfile.mkdtemp()
+
+  def __enter__(self):
+    return self._name
+
+  def __exit__(self, exc, value, tb):
+    if self._name and not self._closed:
+      shutil.rmtree(self._name)
+      self._closed = True
+
+
+def Run(cmd):
+  print 'Running:', ' '.join(cmd)
+  sub = subprocess.Popen(cmd, stdout=subprocess.PIPE, stderr=subprocess.PIPE)
+  return sub.communicate()
+
+def FixErrors(filename, missing_deps, deleted_sources):
+  with open(filename) as f:
+    lines = f.readlines()
+
+  fixed_file = ''
+  indentation_level = None
+  for line in lines:
+    match = TARGET_RE.match(line)
+    if match:
+      target = match.group('target_name')
+      if target in missing_deps:
+        indentation_level = match.group('indentation_level')
+    elif indentation_level is not None:
+      match = re.match(indentation_level + '}$', line)
+      if match:
+        line = ('deps = [\n' +
+                ''.join('  "' + dep + '",\n' for dep in missing_deps[target]) +
+                ']\n') + line
+        indentation_level = None
+      elif line.strip().startswith('deps'):
+        is_empty_deps = line.strip() == 'deps = []'
+        line = 'deps = [\n' if is_empty_deps else line
+        line += ''.join('  "' + dep + '",\n' for dep in missing_deps[target])
+        line += ']\n' if is_empty_deps else ''
+        indentation_level = None
+
+    if line.strip() not in deleted_sources:
+      fixed_file += line
+
+  with open(filename, 'w') as f:
+    f.write(fixed_file)
+
+  Run(['gn', 'format', filename])
+
+def Rebase(base_path, dependency_path, dependency):
+  base_path = base_path.split(os.path.sep)
+  dependency_path = dependency_path.split(os.path.sep)
+
+  first_difference = None
+  shortest_length = min(len(dependency_path), len(base_path))
+  for i in range(shortest_length):
+    if dependency_path[i] != base_path[i]:
+      first_difference = i
+      break
+
+  first_difference = first_difference or shortest_length
+  base_path = base_path[first_difference:]
+  dependency_path = dependency_path[first_difference:]
+  return (os.path.sep.join((['..'] * len(base_path)) + dependency_path) +
+          ':' + dependency)
+
+def main():
+  deleted_sources = set()
+  errors_by_file = defaultdict(lambda: defaultdict(set))
+
+  with TemporaryDirectory() as tmp_dir:
+    mb_gen_command = ([
+        'tools/mb/mb.py', 'gen',
+        tmp_dir,
+        '--config-file', 'webrtc/build/mb_config.pyl',
+    ] + sys.argv[1:])
+
+  mb_output = Run(mb_gen_command)
+  errors = mb_output[0].split('ERROR')[1:]
+
+  if mb_output[1]:
+    print mb_output[1]
+    return 1
+
+  for error in errors:
+    error = error.splitlines()
+    target_msg = 'The target:'
+    if target_msg not in error:
+      target_msg = 'It is not in any dependency of'
+    if target_msg not in error:
+      print '\n'.join(error)
+      continue
+    index = error.index(target_msg) + 1
+    path, target = error[index].strip().split(':')
+    if error[index+1] in ('is including a file from the target:',
+                          'The include file is in the target(s):'):
+      dep = error[index+2].strip()
+      dep_path, dep = dep.split(':')
+      dep = Rebase(path, dep_path, dep)
+      path = os.path.join(path[2:], 'BUILD.gn')
+      errors_by_file[path][target].add(dep)
+    elif error[index+1] == 'has a source file:':
+      deleted_file = '"' + os.path.basename(error[index+2].strip()) + '",'
+      deleted_sources.add(deleted_file)
+    else:
+      print '\n'.join(error)
+      continue
+
+  for path, missing_deps in errors_by_file.items():
+    FixErrors(path, missing_deps, deleted_sources)
+
+  return 0
+
+if __name__ == '__main__':
+  sys.exit(main())