Fix "implements in RHS file"

Source/bindings/scripts/compute_interfaces_info.py

 #!/usr/bin/python
 #
 # Copyright (C) 2013 Google Inc. All rights reserved.
 #
 # Redistribution and use in source and binary forms, with or without
 # modification, are permitted provided that the following conditions are
 # met:
 #
 #     * Redistributions of source code must retain the above copyright
 # notice, this list of conditions and the following disclaimer.
@@ skipping 155 matching lines @@
 
     # Handle partial interfaces
     partial_interface_name = get_partial_interface_name_from_idl(idl_file_contents)
     if partial_interface_name:
         add_paths_to_partials_dict(partial_interface_name, full_path, this_include_path)
         return
 
     # If not a partial interface, the basename is the interface name
     interface_name, _ = os.path.splitext(os.path.basename(idl_filename))
 
+    # 'implements' statements can be included in either the file for the
+    # implement*ing* interface (lhs of 'implements') or implement*ed* interface
+    # (rhs of 'implements'). Store both for now, then merge to implement*ing*
+    # interface later.
     left_interfaces, right_interfaces = get_implements_from_idl(idl_file_contents, interface_name)
 
     interfaces_info[interface_name] = {
         'full_path': full_path,
         'implemented_as': implemented_as,
+        'implemented_by_interfaces': left_interfaces,  # private, merged to next
         'implements_interfaces': right_interfaces,
         'include_path': this_include_path,
         # FIXME: temporary private field, while removing old treatement of
         # 'implements': http://crbug.com/360435
         'is_legacy_treat_as_partial_interface': 'LegacyTreatAsPartialInterface' in extended_attributes,
         'is_callback_interface': is_callback_interface_from_idl(idl_file_contents),
         # Interfaces that are referenced (used as types) and that we introspect
         # during code generation (beyond interface-level data ([ImplementedAs],
         # is_callback_interface, ancestors, and inherited extended attributes):
         # deep dependencies.
         # These cause rebuilds of referrers, due to the dependency, so these
         # should be minimized; currently only targets of [PutForwards].
         'referenced_interfaces': get_put_forward_interfaces_from_idl(idl_file_contents),
     }
 
-    for left_interface_name in left_interfaces:
-        interface_info = interfaces_info[left_interface_name]

[Nils Barth (inactive), 2014/05/08 06:31:45]

This fails with
KeyError: 'Window'
...on r-b-t for me, because Window appears on the rhs before we've reached it.

-        interface_info['implements_interfaces'].append(interface_name)
-
     # Record inheritance information
     inherited_extended_attributes_by_interface[interface_name] = dict(
             (key, value)
             for key, value in extended_attributes.iteritems()
             if key in INHERITED_EXTENDED_ATTRIBUTES)
     parent = get_parent_interface(idl_file_contents)
     if parent:
         parent_interfaces[interface_name] = parent
 
 
@@ skipping 29 matching lines @@
         compute_individual_info(idl_filename)
 
     # Once all individual files handled, can compute inheritance information
     # and dependencies
 
     # Compute inheritance info
     for interface_name in interfaces_info:
         compute_inheritance_info(interface_name)
 
     # Compute dependencies
+    # Move implements info from implement*ed* interface (rhs of 'implements')
+    # to implement*ing* interface (lhs of 'implements').
+    # Note that moving an 'implements' statement between implementing and
+    # implemented files does not change the info (or hence cause a rebuild)!
+    for right_interface_name, interface_info in interfaces_info.iteritems():
+        for left_interface_name in interface_info['implemented_by_interfaces']:
+            interfaces_info[left_interface_name]['implements_interfaces'].append(right_interface_name)
+        del interface_info['implemented_by_interfaces']

[Nils Barth (inactive), 2014/05/08 06:31:45]

We *move* the info, not just copying it, which means moving 'implements' doesn't
even trigger a rebuild!

+
     # An IDL file's dependencies are partial interface files that extend it,
     # and files for other interfaces that this interfaces implements.
     for interface_name, interface_info in interfaces_info.iteritems():
         partial_interface_paths = partial_interface_files[interface_name]
         partial_interfaces_full_paths = partial_interface_paths['full_paths']
         # Partial interface definitions each need an include, as they are
         # implemented in separate classes from the main interface.
         partial_interfaces_include_paths = partial_interface_paths['include_paths']
 
         implemented_interfaces = interface_info['implements_interfaces']
@@ skipping 44 matching lines @@
     idl_files.extend(args)
 
     compute_interfaces_info(idl_files)
     write_pickle_file(options.interfaces_info_file,
                       interfaces_info,
                       options.write_file_only_if_changed)
 
 
 if __name__ == '__main__':
     sys.exit(main())