[Schema Compiler] Separate out SchemaLoader and namespace resolving

tools/json_schema_compiler/namespace_resolver.py

-# Copyright (c) 2012 The Chromium Authors. All rights reserved.
+# 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 re
-import sys
 
-import idl_schema
-import json_schema
 from cpp_namespace_environment import CppNamespaceEnvironment
 from model import Model, UnixName
+from schema_loader import SchemaLoader
 
-def GenerateFilenames(full_namespace):
+
+def _GenerateFilenames(full_namespace):
   # Try to find the file defining the namespace. Eg. for
   # nameSpace.sub_name_space.Type' the following heuristics looks for:
   # 1. name_space_sub_name_space.json,
   # 2. name_space_sub_name_space.idl,
   # 3. sub_name_space.json,
   # 4. sub_name_space.idl,
   # 5. etc.
   sub_namespaces = full_namespace.split('.')
   filenames = [ ]
   basename = None
   for namespace in reversed(sub_namespaces):
     if basename is not None:
       basename = UnixName(namespace + '.' + basename)
     else:
       basename = UnixName(namespace)
     for ext in ['json', 'idl']:
       filenames.append('%s.%s' % (basename, ext))
   return filenames
 
-class SchemaLoader(object):
+
+class NamespaceResolver(object):
   '''Resolves a type name into the namespace the type belongs to.
-
-  Properties:
   - |root| path to the root directory.
   - |path| path to the directory with the API header files, relative to the
     root.
   - |include_rules| List containing tuples with (path, cpp_namespace_pattern)
     used when searching for types.
   - |cpp_namespace_pattern| Default namespace pattern
   '''
-  def __init__(self,
-               root,
-               path,
-               include_rules,
-               cpp_namespace_pattern):
+  def __init__(self, root, path, include_rules, cpp_namespace_pattern):
     self._root = root
-    self._include_rules = [(path, cpp_namespace_pattern)]
-    self._include_rules.extend(include_rules)
+    self._include_rules = [(path, cpp_namespace_pattern)] + include_rules
 
   def ResolveNamespace(self, full_namespace):
-    filenames = GenerateFilenames(full_namespace)
+    '''Returns the model.Namespace object associated with the |full_namespace|,
+    or None if one can't be found.
+    '''
+    filenames = _GenerateFilenames(full_namespace)
     for path, cpp_namespace in self._include_rules:
       cpp_namespace_environment = None
       if cpp_namespace:
         cpp_namespace_environment = CppNamespaceEnvironment(cpp_namespace)
       for filename in reversed(filenames):
         filepath = os.path.join(path, filename);
         if os.path.exists(os.path.join(self._root, filepath)):
+          schema = SchemaLoader(self._root).LoadSchema(filepath)[0]
           return Model().AddNamespace(
-              self.LoadSchema(filepath)[0],
+              schema,
               filepath,
               environment=cpp_namespace_environment)
     return None
 
   def ResolveType(self, full_name, default_namespace):
+    '''Returns the model.Namespace object where the type with the given
+    |full_name| is defined, or None if one can't be found.
+    '''
     name_parts = full_name.rsplit('.', 1)
     if len(name_parts) == 1:
       if full_name not in default_namespace.types:
         return None
       return default_namespace
     full_namespace, type_name = full_name.rsplit('.', 1)
     namespace = self.ResolveNamespace(full_namespace)
     if namespace and type_name in namespace.types:
       return namespace
     return None
-
-  def LoadSchema(self, schema):
-    '''Load a schema definition. The schema parameter must be a file name
-    with the full path relative to the root.'''
-    _, schema_extension = os.path.splitext(schema)
-
-    schema_path = os.path.join(self._root, schema)
-    if schema_extension == '.json':
-      api_defs = json_schema.Load(schema_path)
-    elif schema_extension == '.idl':
-      api_defs = idl_schema.Load(schema_path)
-    else:
-      sys.exit('Did not recognize file extension %s for schema %s' %
-               (schema_extension, schema))
-
-    return api_defs