Add "implemented_in" key in IDL schema compiler

tools/json_schema_compiler/idl_schema.py

 #! /usr/bin/env python
 # Copyright (c) 2012 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 itertools
 import json
 import os.path
 import re
 import sys
@@ skipping 306 matching lines @@
   '''
   Given an IDLNode representing an IDL namespace, converts into a Python
   dictionary that the JSON schema compiler expects to see.
   '''
 
   def __init__(self,
                namespace_node,
                description,
                nodoc=False,
                internal=False,
-               platforms=None):
+               platforms=None,
+               compiler_options=None):
     self.namespace = namespace_node
     self.nodoc = nodoc
     self.internal = internal
     self.platforms = platforms
+    self.compiler_options = compiler_options
     self.events = []
     self.functions = []
     self.types = []
     self.callbacks = OrderedDict()
     self.description = description
 
   def process(self):
     for node in self.namespace.children:
       if node.cls == 'Dictionary':
         self.types.append(Dictionary(node).process(self.callbacks))
       elif node.cls == 'Callback':
         k, v = Member(node).process(self.callbacks)
         self.callbacks[k] = v
       elif node.cls == 'Interface' and node.GetName() == 'Functions':
         self.functions = self.process_interface(node)
       elif node.cls == 'Interface' and node.GetName() == 'Events':
         self.events = self.process_interface(node)
       elif node.cls == 'Enum':
         self.types.append(Enum(node).process(self.callbacks))
       else:
         sys.exit('Did not process %s %s' % (node.cls, node))
     return {'namespace': self.namespace.GetName(),
             'description': self.description,
             'nodoc': self.nodoc,
             'types': self.types,
             'functions': self.functions,
             'internal': self.internal,
             'events': self.events,
-            'platforms': self.platforms}
+            'platforms': self.platforms,
+            'compiler_options': {}
+               if not self.compiler_options else self.compiler_options}

[sergeygs, 2013/11/02 06:20:44]

I'd prefer:

'compiler_options': self.compiler_options or {}

It's a common idiom in Python and it's a lot simpler. Also, conditional
expressions are restricted to one-liners in Google guide, while you have 2 lines

(https://engdoc.corp.google.com/eng/doc/pyguide.xml?showone=Conditional_Expres...)

[Haojian Wu, 2013/11/03 01:56:16]

Done.

[not at google - send to devlin, 2013/11/04 15:16:49]

The problem with "self.compiler_options or {}" is that the behaviour subtly
changes if self._compiler_options is an empty object (vs None), because bool({})
is false. This is why being explicit in the object case is every-so-slighly
safer, generally speaking. "foo or Foo()" is great when bool(Foo()) is true.

If the two-line-conditional is a problem then assign it outside the loop.

 
   def process_interface(self, node):
     members = []
     for member in node.children:
       if member.cls == 'Member':
         name, properties = Member(member).process(self.callbacks)
         members.append(properties)
     return members
 
 
 class IDLSchema(object):
   '''
   Given a list of IDLNodes and IDLAttributes, converts into a Python list
   of api_defs that the JSON schema compiler expects to see.
   '''
 
   def __init__(self, idl):
     self.idl = idl
 
   def process(self):
     namespaces = []
     nodoc = False
     internal = False
     description = None
     platforms = None
+    compiler_options = None
     for node in self.idl:
       if node.cls == 'Namespace':
         if not description:
           # TODO(kalman): Go back to throwing an error here.
           print('%s must have a namespace-level comment. This will '
                            'appear on the API summary page.' % node.GetName())
           description = ''
-        namespace = Namespace(node, description, nodoc, internal, platforms)
+        namespace = Namespace(node, description, nodoc, internal,
+            platforms=platforms, compiler_options=compiler_options)

[sergeygs, 2013/11/02 06:20:44]

Align 'platform...' with 'node' in the preceding line. I think you will also
have to move 'compiler_options' to new line then as well. Google style guide is
silent about this, but PEP 8 is explicit:
http://www.python.org/dev/peps/pep-0008/#indentation.

[Haojian Wu, 2013/11/03 01:56:16]

Done. Thanks for the link.

         namespaces.append(namespace.process())
         nodoc = False
         internal = False
         platforms = None
+        compiler_options = None
       elif node.cls == 'Copyright':
         continue
       elif node.cls == 'Comment':
         description = node.GetName()
       elif node.cls == 'ExtAttribute':
         if node.name == 'nodoc':
           nodoc = bool(node.value)
         elif node.name == 'internal':
           internal = bool(node.value)
         elif node.name == 'platforms':
           platforms = list(node.value)
+        elif node.name == 'implemented_in':
+          compiler_options = {"implemented_in": node.value}

[sergeygs, 2013/11/02 06:20:44]

Please use single quotes here: { 'implemented_in': node.value }. It's a frequent
Python convention to use double quotes for plain language and/or interpolated
strings, and single quotes for identifiers that would result in a logical or
runtime error if misspelled. I can't say we stick to that in our code, but if
anything, we favor single quotes, specifically in the surrounding code in this
file and others in this CL.

[Haojian Wu, 2013/11/03 01:56:16]

Done. Thanks for the detailed explainations.

         else:
           continue
       else:
         sys.exit('Did not process %s %s' % (node.cls, node))
     return namespaces
 
 
 def Load(filename):
   '''
   Given the filename of an IDL file, parses it and returns an equivalent
@@ skipping 14 matching lines @@
   Dump a json serialization of parse result for the IDL files whose names
   were passed in on the command line.
   '''
   for filename in sys.argv[1:]:
     schema = Load(filename)
     print json.dumps(schema, indent=2)
 
 
 if __name__ == '__main__':
   Main()