[Extension API Extern Generation] Fix a few bugs in extern generation

tools/json_schema_compiler/js_externs_generator.py

 # Copyright 2015 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.
 """
 Generator that produces an externs file for the Closure Compiler.
 Note: This is a work in progress, and generated externs may require tweaking.
 
 See https://developers.google.com/closure/compiler/docs/api-tutorial3#externs
 """
 
@@ skipping 108 matching lines @@
     c = Code()
     c.Append('@typedef {')
     c.Concat(self._GenerateObjectDefinition(properties), new_line=False)
     c.Append('}', new_line=False)
     return c
 
   def _GenerateObjectDefinition(self, properties):
     """Given an OrderedDict of properties, returns a Code containing the
        description of an object.
     """
-    if not properties: return ''
+    if not properties: return Code()
 
     c = Code()
     c.Sblock('{')
     first = True
     for field, prop in properties.items():
       # Avoid trailing comma.
       # TODO(devlin): This will be unneeded, if/when
       # https://github.com/google/closure-compiler/issues/796 is fixed.
       if not first:
         c.Append(',', new_line=False)
@@ skipping 69 matching lines @@
       c.Append('void', new_line=False)
 
     return c
 
   def _TypeToJsType(self, js_type):
     """Converts a model.Type to a JS type (number, Array, etc.)"""
     c = Code()
     if js_type.property_type in (PropertyType.INTEGER, PropertyType.DOUBLE):
       c.Append('number')
     elif js_type.property_type is PropertyType.OBJECT:
-      c = self._GenerateObjectDefinition(js_type.properties)
+      if js_type.properties:
+        c = self._GenerateObjectDefinition(js_type.properties)

[Dan Beam, 2015/04/07 01:54:46]

this is OK i guess but it might be mildly better if we just returned the result
right away from each elif, IMO

[Devlin, 2015/04/07 16:13:27]

Yeah, I guess "return Code().Append('foo')" isn't much worse than
"c.Append('foo')", and it makes it more clear in the cases we just return the
result of another method (like here).  Done.

+      else:
+        c.Append('Object')
     elif js_type.property_type is PropertyType.ARRAY:
       (c.Append('!Array<').
            Concat(self._TypeToJsType(js_type.item_type), new_line=False).
            Append('>', new_line=False))
     elif js_type.property_type is PropertyType.REF:
       ref_type = js_type.ref_type
       # Enums are defined as chrome.fooAPI.MyEnum, but types are defined simply
       # as MyType.
       if self._namespace.types[ref_type].property_type is PropertyType.ENUM:
         ref_type = '!chrome.%s.%s' % (self._namespace.name, ref_type)
@@ skipping 76 matching lines @@
     """Generates a @see link for a given API 'object' (type, method, or event).
     """
 
     # NOTE(devlin): This is kind of a hack. Some APIs will be hosted on
     # developer.chrome.com/apps/ instead of /extensions/, and some APIs have
     # '.'s in them (like app.window), which should resolve to 'app_window'.
     # Luckily, the doc server has excellent url resolution, and knows exactly
     # what we mean. This saves us from needing any complicated logic here.
     return ('@see https://developer.chrome.com/extensions/%s#%s-%s' %
                 (self._namespace.name, object_type, object_name))