Mojo: Simplify typemap usage.

mojo/public/tools/bindings/generate_type_mappings.py

Index: mojo/public/tools/bindings/generate_type_mappings.py
diff --git a/mojo/public/tools/bindings/generate_type_mappings.py b/mojo/public/tools/bindings/generate_type_mappings.py
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+++ b/mojo/public/tools/bindings/generate_type_mappings.py
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+#!/usr/bin/env python
+# 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.
+"""Generates a JSON typemap from its command-line arguments and dependencies.
+
+Each typemap should be specified in an command-line argument of the form
+key=value, with an argument of "--start-typemap" preceding each typemap.
+
+For example,
+generate_type_mappings.py --output=foo.typemap --start-typemap \\
+    public_headers=foo.h traits_headers=foo_traits.h \\
+    type_mappings=mojom.Foo=FooImpl
+
+generates a foo.typemap containing
+{
+  "c++": {
+    "mojom.Foo": {
+      "typename": "FooImpl",
+      "traits_headers": [
+        "foo_traits.h"
+      ],
+      "public_headers": [
+        "foo.h"
+      ]
+    }
+  }
+}
+
+Then,
+generate_type_mappings.py --dependency foo.typemap --output=bar.typemap \\
+    --start-typemap public_headers=bar.h traits_headers=bar_traits.h \\
+    type_mappings=mojom.Bar=BarImpl
+
+generates a bar.typemap containing
+{
+  "c++": {
+    "mojom.Bar": {
+      "typename": "BarImpl",
+      "traits_headers": [
+        "bar_traits.h"
+      ],
+      "public_headers": [
+        "bar.h"
+      ]
+    },
+    "mojom.Foo": {
+      "typename": "FooImpl",
+      "traits_headers": [
+        "foo_traits.h"
+      ],
+      "public_headers": [
+        "foo.h"
+      ]
+    }
+  }
+}
+"""
+
+import argparse
+import json
+import os
+
+
+def ReadTypemap(path):
+  with open(path) as f:
+    return json.load(f)['c++']
+
+
+def ParseTypemapArgs(args):
+  typemaps = [s for s in '\n'.join(args).split('--start-typemap\n') if s]
+  result = {}
+  for typemap in typemaps:
+    result.update(ParseTypemap(typemap))
+  return result
+
+
+def ParseTypemap(typemap):
+  values = {'type_mappings': [], 'public_headers': [], 'traits_headers': []}
+  for line in typemap.split('\n'):
+    if not line:
+      continue
+    key, _, value = line.partition('=')
+    values[key].append(value.lstrip('/'))
+  result = {}
+  for typename in values['type_mappings']:
+    mojom_type, _, native_type = typename.partition('=')
+    result[mojom_type] = {
+        'typename': native_type,
+        'public_headers': values['public_headers'],
+        'traits_headers': values['traits_headers'],
+    }
+  return result
+
+
+def main():
+  parser = argparse.ArgumentParser(
+      description=__doc__,
+      formatter_class=argparse.RawDescriptionHelpFormatter)
+  parser.add_argument(
+      '--dependency',
+      type=str,
+      action='append',
+      default=[],
+      help=('A path to another JSON typemap to merge into the output. '
+            'This may be repeated to merge multiple typemaps.'))
+  parser.add_argument('--output',
+                      type=str,
+                      required=True,
+                      help='The path to which to write the generated JSON.')
+  params, typemap_params = parser.parse_known_args()
+  typemaps = ParseTypemapArgs(typemap_params)
+  missing = [path for path in params.dependency if not os.path.exists(path)]
+  if missing:
+    raise IOError('Missing dependencies: %s' % ', '.join(missing))
+  for path in params.dependency:
+    typemaps.update(ReadTypemap(path))
+  with open(params.output, 'w') as f:
+    json.dump({'c++': typemaps}, f, indent=2)
+
+
+if __name__ == '__main__':
+  main()