Auto generate UseCounter::Feature enum from an .in file

Source/build/scripts/make_use_counter.py

+#!/usr/bin/env python
+
+# 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.
+
+import media_feature_symbol
+import in_generator
+import template_expander
+import name_utilities
+import sys
+
+
+feature_values = set()
+
+
+def unique_value(value, feature):
+    global feature_values
+    if not value or type(value) is bool:

[haraken, 2014/11/24 09:38:49]

Just help me understand: What is the 'type(value) is bool' check for?

+        print "'%s' values isn't defined, please define it!" % feature
+        exit(1)
+    if value in feature_values:
+        print "'%s' value is already defined, please change it!" % feature
+        exit(1)
+    feature_values.add(value)
+    return value
+
+
+class MakeUseCounterWriter(in_generator.Writer):
+    defaults = {
+        'value': None,
+    }
+    filters = {
+        'unique_value': unique_value,
+    }
+    default_parameters = {
+        'value': '',
+    }
+
+    def __init__(self, in_file_path):
+        super(MakeUseCounterWriter, self).__init__(in_file_path)
+

[Timothy Loh, 2014/11/24 11:02:40]

The whole unique_value thing is a bit awkward, why don't we just write here
something like:

self.features = self.in_file.name_dictionaries

feature_values = set(feature['value'] for feature in self.features)
assert None not in feature_values, "All features should be given values"
assert len(features_values) == len(self.features), "Features should have unique
values"

The error reporting is slightly less useful here, but since you normally only
modify one flag it'll probably be obvious what's wrong.

+        self._outputs = {
+            ('UseCounterGenerated.h'): self.generate_header,

[Timothy Loh, 2014/11/24 11:02:40]

Unneeded brackets here

+        }
+        self._template_context = {

[Timothy Loh, 2014/11/24 11:02:40]

This dict makes more sense to just have inline in generate_header

+            'features': self.in_file.name_dictionaries,
+        }
+
+    @template_expander.use_jinja('UseCounterGenerated.h.tmpl', filters=filters)
+    def generate_header(self):
+        return self._template_context
+
+if __name__ == '__main__':
+    in_generator.Maker(MakeUseCounterWriter).main(sys.argv)