mojo: Generate top level enums for python bindings.

mojo/public/python/mojo/bindings/reflection.py

Index: mojo/public/python/mojo/bindings/reflection.py
diff --git a/mojo/public/python/mojo/bindings/reflection.py b/mojo/public/python/mojo/bindings/reflection.py
new file mode 100644
index 0000000000000000000000000000000000000000..95e0c7bdb0dac52b7057014c60af4f1f307d29eb
--- /dev/null
+++ b/mojo/public/python/mojo/bindings/reflection.py
@@ -0,0 +1,40 @@
+# Copyright 2014 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.
+
+"""The meta classes used by the mojo python bindings."""
+
+class MojoEnumType(type):
+  """Meta class for enumerations.
+
+  Usage:
+    class MyEnum(object):
+      __metaclass__ = MojoEnumType
+      VALUES = [
+        ('A', 0),
+        'B',
+        ('C', 5),
+      ]
+
+      This will define a enum with 3 values, A = 0, B = 1 and C = 5.
+  """
+  def __new__(mcs, name, bases, dictionary):
+    class_members = {
+      '__new__': None,
+    }
+    current_enum_value = 0
+    for value in dictionary.pop('VALUES', []):
+      if isinstance(value, str):
+        key, enum_value = value, current_enum_value
+      elif isinstance(value, tuple):
+        key, enum_value = value
+      else:
+        raise ValueError('incorrect value: %r' % value)
+      if isinstance(key, str) and isinstance(enum_value, int):
+        class_members[key], current_enum_value = enum_value, enum_value + 1

[pkl (ping after 24h if needed), 2014/09/04 18:07:20]

This is going to silently overwrite previously defined enums. Do you want to
have error check on class_members.has_key(key) before you do this assignment?

[qsr, 2014/09/05 11:46:02]

 Not really, if that happens, that must be caught at a higher level, not by each
individual code generators.

+      else:
+        raise ValueError('incorrect value: %r' % value)
+    return type.__new__(mcs, name, bases, class_members)
+
+  def __setattr__(mcs, key, value):
+    raise NotImplementedError