externs: refactor the list of generated externs

This makes the externs util code easier to use by other presubmit
tests by reducing a lot of boilerplate.

This also enforces a rule that was being used in practice: the input
& output names have to match (other than file extension).  So instead
of letting the code map "downloads.idl" to the externs "whatever.js"
name, the output must now always be "downloads.js".

If we ignore the Chromecast & app_shell forks of the Chromium project,
this rule holds.  Those forks cause problems by providing extensions
to a few APIs and thus use duplicate source names.  imo, those forks
should be providing their own separate externs tree if they want to
provide externs (which they don't currently), although I suspect the
users are so few that no one will bother.

Bug: 469920
Change-Id: Icb9d2ba4ad78c3c607a09402c82841fb745b4b78
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2215901
Commit-Queue: Mike Frysinger <vapier@chromium.org>
Reviewed-by: Devlin <rdevlin.cronin@chromium.org>
Cr-Commit-Position: refs/heads/master@{#771917}

chrome/common/extensions/api/PRESUBMIT.py

@@ -13,47 +13,15 @@ import sys
 
 def _CheckExterns(input_api, output_api):
   original_sys_path = sys.path
-
   join = input_api.os_path.join
-  api_root = input_api.PresubmitLocalPath()
-  src_root = join(api_root, '..', '..', '..', '..')
+  src_root = input_api.change.RepositoryRoot()
   try:
     sys.path.append(join(src_root, 'extensions', 'common', 'api'))
     from externs_checker import ExternsChecker
   finally:
     sys.path = original_sys_path
 
-  externs_root = join(src_root, 'third_party', 'closure_compiler', 'externs')
-
-  api_pair_names = {
-    'accessibility_private.json': 'accessibility_private.js',
-    'activity_log_private.json': 'activity_log_private.js',
-    'autofill_private.idl': 'autofill_private.js',
-    'developer_private.idl': 'developer_private.js',
-    'bookmark_manager_private.json': 'bookmark_manager_private.js',
-    'command_line_private.json': 'command_line_private.js',
-    'file_manager_private.idl': 'file_manager_private.js',
-    'file_system_provider.idl': 'file_system_provider.js',
-    'input_method_private.json': 'input_method_private.js',
-    'language_settings_private.idl': 'language_settings_private.js',
-    'media_player_private.json': 'media_player_private.js',
-    'passwords_private.idl': 'passwords_private.js',
-    'quick_unlock_private.idl': 'quick_unlock_private.js',
-    'resources_private.idl': 'resources_private.js',
-    'safe_browsing_private.idl': 'safe_browsing_private.js',
-    'settings_private.idl': 'settings_private.js',
-    'system_private.json': 'system_private.js',
-    'terminal_private.json': 'terminal_private.js',
-    'users_private.idl': 'users_private.js',
-    # TODO(rdevlin.cronin): Add more!
-  }
-  normpath = input_api.os_path.normpath
-  api_pairs = {
-      normpath(join(api_root, k)):
-          normpath(join(externs_root, v)) for k, v in api_pair_names.items()
-  }
-
-  return ExternsChecker(input_api, output_api, api_pairs).RunChecks()
+  return ExternsChecker(input_api, output_api).RunChecks()
 
 
 def CheckChangeOnUpload(input_api, output_api):

chrome/common/extensions/api/generated_externs_list.txt

+# All APIs that have their externs generated.
+# TODO(rdevlin.cronin): Add more!
+accessibility_private.json
+activity_log_private.json
+autofill_private.idl
+bookmark_manager_private.json
+command_line_private.json
+developer_private.idl
+file_manager_private.idl
+file_system_provider.idl
+input_method_private.json
+language_settings_private.idl
+media_player_private.json
+passwords_private.idl
+quick_unlock_private.idl
+resources_private.idl
+safe_browsing_private.idl
+settings_private.idl
+system_private.json
+terminal_private.json
+users_private.idl

extensions/common/api/PRESUBMIT.py

@@ -13,38 +13,13 @@ 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 = input_api.os_path.abspath(join(
-      api_root, '..', '..', '..', 'third_party', 'closure_compiler', 'externs'))
-
-  api_pairs = {
-    join(api_root, 'audio.idl'): join(externs_root, 'audio.js'),
-    join(api_root, 'automation.idl'): join(externs_root, 'automation.js'),
-    join(api_root, 'bluetooth.idl'): join(externs_root, 'bluetooth.js'),
-    join(api_root, 'bluetooth_private.idl'):
-        join(externs_root, 'bluetooth_private.js'),
-    join(api_root, 'clipboard.idl'): join(externs_root, 'clipboard.js'),
-    join(api_root, 'management.json'): join(externs_root, 'management.js'),
-    join(api_root, 'metrics_private.json'):
-        join(externs_root, 'metrics_private.js'),
-    join(api_root, 'mime_handler_private.idl'):
-        join(externs_root, 'mime_handler_private.js'),
-    join(api_root, 'networking_private.idl'):
-        join(externs_root, 'networking_private.js'),
-    join(api_root, 'system_display.idl'):
-        join(externs_root, 'system_display.js'),
-    # TODO(rdevlin.cronin): Add more!
-  }
-
-  return ExternsChecker(input_api, output_api, api_pairs).RunChecks()
+  return ExternsChecker(input_api, output_api).RunChecks()
 
 
 def CheckChangeOnUpload(input_api, output_api):

extensions/common/api/externs_checker.py

@@ -7,7 +7,10 @@ class ExternsChecker(object):
  src/ $ python tools/json_schema_compiler/compiler.py\
  %s --root=. --generator=externs > %s"""
 
-  def __init__(self, input_api, output_api, api_pairs):
+  def __init__(self, input_api, output_api, api_pairs=None, api_root=None):
+    if api_pairs is None:
+      api_pairs = self.ParseApiFileList(input_api, api_root=api_root)
+
     self._input_api = input_api
     self._output_api = output_api
     self._api_pairs = api_pairs
@@ -16,6 +19,31 @@ class ExternsChecker(object):
       if not input_api.os_path.exists(path):
         raise OSError('Path Not Found: %s' % path)
 
+  @staticmethod
+  def ParseApiFileList(input_api, api_root=None):
+    """Extract the API pairs from the registered list."""
+    if api_root is None:
+      api_root = input_api.PresubmitLocalPath()
+    externs_root = input_api.os_path.join(
+        input_api.change.RepositoryRoot(), 'third_party', 'closure_compiler',
+        'externs')
+
+    ret = {}
+    listing = input_api.os_path.join(api_root, 'generated_externs_list.txt')
+    for line in input_api.ReadFile(listing).splitlines():
+      # Skip blank & comment lines.
+      if not line.split('#', 1)[0].strip():
+        continue
+
+      source = input_api.os_path.join(api_root, line)
+      api_name, ext = line.rsplit('.', 1)
+      assert ext == 'json' or ext == 'idl'
+      externs = input_api.os_path.join(externs_root, api_name + '.js')
+      ret[source] = externs
+
+    assert ret
+    return ret
+
   def RunChecks(self):
     bad_files = []
     affected = [f.AbsoluteLocalPath() for f in

extensions/common/api/generated_externs_list.txt

+# APIs that have their externs generated.
+# TODO(rdevlin.cronin): Add more!
+audio.idl
+automation.idl
+bluetooth.idl
+bluetooth_private.idl
+clipboard.idl
+management.json
+metrics_private.json
+mime_handler_private.idl
+networking_private.idl
+system_display.idl