Supporting more APIs with json_schema_compiler

tools/json_schema_compiler/code.py

 # 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.
 
 class Code(object):
   """A convenience object for constructing code.
 
   Logically each object should be a block of code. All methods except |Render|
   and |IsEmpty| return self.
   """
@@ skipping 17 matching lines @@
 
   def Concat(self, obj):
     """Concatenate another Code object onto this one. Trailing whitespace is
     stripped.
 
     Appends the code at the current indent level. Will fail if there are any
     un-interpolated format specifiers eg %s, %(something)s which helps
     isolate any strings that haven't been substituted.
     """
     if not isinstance(obj, Code):
-      raise TypeError()
+      raise TypeError(type(obj))
     assert self is not obj
     for line in obj._code:
-      # line % () will fail if any substitution tokens are left in line
-      self._code.append(((' ' * self._indent_level) + line % ()).rstrip())
+      try:
+        # line % () will fail if any substitution tokens are left in line
+        self._code.append(((' ' * self._indent_level) + line % ()).rstrip())
+      except TypeError:
+        raise TypeError('Unsubstituted value when concatting\n' + line)
 
     return self
 
   def Sblock(self, line=''):
     """Starts a code block.
 
     Appends a line of code and then increases the indent level.
     """
     self.Append(line)
     self._indent_level += self._indent_size
@@ skipping 50 matching lines @@
         raise TypeError('"%s" or "%r" found in substitution. '
                         'Named arguments only. Use "%" to escape')
       self._code[i] = line % d
     return self
 
   def Render(self):
     """Renders Code as a string.
     """
     return '\n'.join(self._code)