[Extern Generation] Add a presubmit script to check externs not being updated

Add a presubmit script that checks for when extension api files are touched, but
the corresponding extern file is not. Right now, this is very simple - it only
checks that the extern is modified in some way (doesn't validate that it's the
*right* way), and is only a warning (because sometimes api file changes don't
cause extern changes). As an improvement, we would validate that the extern
files contain the proper content - let's do that later.

This will also be rolled out piecemeal, since many APIs don't currently have a
dedicated extern file. This change only imposes the check on bluetooth (because
it was handy) - if all goes well, we'll roll this out to all api files.

Also establish a dedicated extern folder, since it's silly for chrome-generated
externs to live in third_party/.

BUG=469920

Review URL: https://codereview.chromium.org/1718243003

Cr-Commit-Position: refs/heads/master@{#378018}

3 files changed, 132 insertions, 0 deletions

diff --git a/extensions/common/api/PRESUBMIT.py b/extensions/common/api/PRESUBMIT.py
new file mode 100644
index 0000000..b74059f
--- /dev/null
+++ b/extensions/common/api/PRESUBMIT.py
@@ -0,0 +1,37 @@
+# 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.
+
+"""Chromium presubmit script for src/extensions/common.
+
+See http://dev.chromium.org/developers/how-tos/depottools/presubmit-scripts
+for more details on the presubmit API built into depot_tools.
+"""
+
+import sys
+
+
+def _CheckExterns(input_api, output_api):
+  original_sys_path = sys.path
+
+  try:
+    sys.path.append(input_api.PresubmitLocalPath())
+    from externs_checker import ExternsChecker
+  finally:
+    sys.path = original_sys_path
+
+  join = input_api.os_path.join
+  api_root = input_api.PresubmitLocalPath()
+  externs_root = join(api_root, '..', '..', '..', 'third_party',
+      'closure_compiler', 'externs')
+
+  api_pairs = {
+    join(api_root, 'bluetooth.idl'): join(externs_root, 'bluetooth.js'),
+    # TODO(rdevlin.cronin): Add more!
+  }
+
+  return ExternsChecker(input_api, output_api, api_pairs).RunChecks()
+
+
+def CheckChangeOnUpload(input_api, output_api):
+  return _CheckExterns(input_api, output_api)
diff --git a/extensions/common/api/externs_checker.py b/extensions/common/api/externs_checker.py
new file mode 100644
index 0000000..58c0076
--- /dev/null
+++ b/extensions/common/api/externs_checker.py
@@ -0,0 +1,32 @@
+# 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.
+
+class ExternsChecker(object):
+  _UPDATE_MESSAGE = """To update the externs, run:
+ src/ $ python tools/json_schema_compiler/compiler.py\
+ %s --root=. --generator=externs > %s"""
+
+  def __init__(self, input_api, output_api, api_pairs):
+    self._input_api = input_api
+    self._output_api = output_api
+    self._api_pairs = api_pairs
+
+  def RunChecks(self):
+    bad_files = []
+    affected = [f.AbsoluteLocalPath() for f in self._input_api.AffectedFiles()]
+    for path in affected:
+      pair = self._api_pairs.get(path)
+      if pair != None and pair not in affected:
+        bad_files.append({'source': path, 'extern': pair})
+    results = []
+    if bad_files:
+      replacements = (('<source_file>', '<output_file>') if len(bad_files) > 1
+          else (bad_files[0]['source'], bad_files[0]['extern']))
+      long_text = self._UPDATE_MESSAGE % replacements
+      results.append(self._output_api.PresubmitPromptWarning(
+          str('Found updated extension api files without updated extern files. '
+              'Please update the extern files.'),
+          [f['source'] for f in bad_files],
+          long_text))
+    return results
diff --git a/extensions/common/api/externs_checker_test.py b/extensions/common/api/externs_checker_test.py
new file mode 100755
index 0000000..73b65fa
--- /dev/null
+++ b/extensions/common/api/externs_checker_test.py
@@ -0,0 +1,63 @@
+#!/usr/bin/env python
+# 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.
+
+import os
+import sys
+import unittest
+
+from externs_checker import ExternsChecker
+
+sys.path.append(
+    os.path.join(os.path.dirname(os.path.abspath(__file__)), '..', '..', '..'))
+
+from PRESUBMIT_test_mocks import MockInputApi, MockOutputApi, MockFile
+
+
+class ExternsCheckerTest(unittest.TestCase):
+  API_PAIRS = {'a': '1', 'b': '2', 'c': '3'}
+
+  def _runChecks(self, files):
+    input_api = MockInputApi()
+    input_api.files = [MockFile(f, '') for f in files]
+    output_api = MockOutputApi()
+    checker = ExternsChecker(input_api, output_api, self.API_PAIRS)
+    return checker.RunChecks()
+
+  def testModifiedSourceWithoutModifiedExtern(self):
+    results = self._runChecks(['b', 'test', 'random'])
+    self.assertEquals(1, len(results))
+    self.assertEquals(1, len(results[0].items))
+    self.assertEquals('b', results[0].items[0])
+    self.assertEquals(
+        'To update the externs, run:\n'
+        ' src/ $ python tools/json_schema_compiler/compiler.py b --root=. '
+        '--generator=externs > 2',
+        results[0].long_text)
+
+  def testModifiedSourceWithModifiedExtern(self):
+    results = self._runChecks(['b', '2', 'test', 'random'])
+    self.assertEquals(0, len(results))
+
+  def testModifiedMultipleSourcesWithNoModifiedExterns(self):
+    results = self._runChecks(['b', 'test', 'c', 'random'])
+    self.assertEquals(1, len(results))
+    self.assertEquals(2, len(results[0].items))
+    self.assertTrue('b' in results[0].items)
+    self.assertTrue('c' in results[0].items)
+    self.assertEquals(
+        'To update the externs, run:\n'
+        ' src/ $ python tools/json_schema_compiler/compiler.py <source_file> '
+        '--root=. --generator=externs > <output_file>',
+        results[0].long_text)
+
+  def testModifiedMultipleSourcesWithOneModifiedExtern(self):
+    results = self._runChecks(['b', 'test', 'c', 'random', '2'])
+    self.assertEquals(1, len(results))
+    self.assertEquals(1, len(results[0].items))
+    self.assertEquals('c', results[0].items[0])
+
+
+if __name__ == '__main__':
+  unittest.main()