Add a presubmit check for boolean policy polarity.

The current situation of boolean policy switches either enabling or
disabling something is pretty arbitrary (although tending to be the
inverse of the browser default). It's much easier to reason about
XYZEnabled-style settings, so we prefer those going forward.

BUG=chromium:85687
TEST=None


Review URL: https://chromiumcodereview.appspot.com/10829197

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@150333 0039d316-1c4b-4281-b951-d872f2087c98

chrome/app/policy/syntax_check_policy_template_json.py

@@ -30,6 +30,26 @@ TYPE_TO_SCHEMA = {
   'string-enum': 'string',
 }
 
+# List of boolean policies that have been introduced with negative polarity in
+# the past and should not trigger the negative polarity check.
+LEGACY_INVERTED_POLARITY_WHITELIST = [
+    'DeveloperToolsDisabled',
+    'DeviceAutoUpdateDisabled',
+    'Disable3DAPIs',
+    'DisableAuthNegotiateCnameLookup',
+    'DisablePluginFinder',
+    'DisablePrintPreview',
+    'DisableSafeBrowsingProceedAnyway',
+    'DisableScreenshots',
+    'DisableSpdy',
+    'DisableSSLRecordSplitting',
+    'ExternalStorageDisabledforrealz',
+    'GDataDisabled',
+    'GDataDisabledOverCellular',
+    'SavingBrowserHistoryDisabled',
+    'SyncDisabled',
+]
+
 class PolicyTemplateChecker(object):
 
   def __init__(self):
@@ -127,10 +147,21 @@ class PolicyTemplateChecker(object):
     self._CheckContains(policy, 'schema', dict)
     if isinstance(policy.get('schema'), dict):
       self._CheckContains(policy['schema'], 'type', str)
-      if policy['schema'].get('type') != TYPE_TO_SCHEMA[policy_type]:
+      schema_type = policy['schema'].get('type')
+      if schema_type != TYPE_TO_SCHEMA[policy_type]:
         self._Error('Schema type must match the existing type for policy %s' %
                     policy.get('name'))
 
+      # Checks that boolean policies are not negated (which makes them harder to
+      # reason about).
+      if (schema_type == 'boolean' and
+          'disable' in policy.get('name').lower() and
+          policy.get('name') not in LEGACY_INVERTED_POLARITY_WHITELIST):
+        self._Error(('Boolean policy %s uses negative polarity, please make ' +
+                     'new boolean policies follow the XYZEnabled pattern. ' +
+                     'See also http://crbug.com/85687') % policy.get('name'))
+
+
   def _CheckPolicy(self, policy, is_in_group, policy_ids):
     if not isinstance(policy, dict):
       self._Error('Each policy must be a dictionary.', 'policy', None, policy)