Generate Sky's _sdkext file using the build system

mojo/public/tools/dart_pkg.py

 #!/usr/bin/env python
 #
 # Copyright 2015 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.
 
 """Utility for dart_pkg and dart_pkg_app rules"""
 
 import argparse
 import errno
+import json
 import os
 import shutil
 import sys
 
 # Disable lint check for finding modules:
 # pylint: disable=F0401
 
 sys.path.insert(0, os.path.join(os.path.dirname(os.path.abspath(__file__)),
                                 "bindings/pylib"))
 
@@ skipping 77 matching lines @@
         dirs[:] = filter(wrapped_filter, dirs)
 
 
 def copy_or_link(from_root, to_root, filter_func=None):
     if USE_LINKS:
         link(from_root, to_root)
     else:
         copy(from_root, to_root, filter_func)
 
 
+def remove_if_exists(path):
+    try:
+        os.remove(path)
+    except OSError as e:
+        if e.errno != errno.ENOENT:
+            raise
+
 def list_files(from_root, filter_func=None):
     file_list = []
     for root, dirs, files in os.walk(from_root):
         # filter_func expects paths not names, so wrap it to make them absolute.
         wrapped_filter = None
         if filter_func:
             wrapped_filter = lambda name: filter_func(os.path.join(root, name))
         for name in filter(wrapped_filter, files):
             path = os.path.join(root, name)
             file_list.append(path)
@@ skipping 67 matching lines @@
     parser.add_argument('--sdk-ext-directories',
                         metavar='sdk_ext_directories',
                         help='Directory containing .dart sources',
                         nargs='*',
                         default=[])
     parser.add_argument('--sdk-ext-files',
                         metavar='sdk_ext_files',
                         help='List of .dart files that are part of of sdk_ext.',
                         nargs='*',
                         default=[])
+    parser.add_argument('--sdk-ext-mappings',
+                        metavar='sdk_ext_mappings',
+                        help='Mappings for SDK extension libraries.',
+                        nargs='*',
+                        default=[])
     args = parser.parse_args()
 
     # We must have a pubspec.yaml.
     assert has_pubspec_yaml(args.package_sources)
 
+    target_dir = os.path.join(args.pkg_directory, args.package_name)
+    lib_path = os.path.join(target_dir, "lib")
+
+    mappings = {}
+    for mapping in args.sdk_ext_mappings:
+        library, path = mapping.split(',', 1)
+        mappings[library] = '../sdk_ext/%s' % path
+
+    sdkext_path = os.path.join(lib_path, '_sdkext')
+    if mappings:
+        with open(sdkext_path, 'w') as stream:
+            json.dump(mappings, stream, sort_keys=True,
+                      indent=2, separators=(',', ': '))
+    else:
+        remove_if_exists(sdkext_path)
+
     # Copy or symlink package sources into pkg directory.
-    target_dir = os.path.join(args.pkg_directory, args.package_name)
     common_source_prefix = os.path.commonprefix(args.package_sources)
     for source in args.package_sources:
         relative_source = os.path.relpath(source, common_source_prefix)
         target = os.path.join(target_dir, relative_source)
         copy_or_link(source, target)
 
     # Copy sdk-ext sources into pkg directory
     sdk_ext_dir = os.path.join(target_dir, 'sdk_ext')
     for directory in args.sdk_ext_directories:
         sdk_ext_sources = list_files(directory, dart_filter)
         common_prefix = os.path.commonprefix(sdk_ext_sources)
         for source in sdk_ext_sources:
             relative_source = os.path.relpath(source, common_prefix)
             target = os.path.join(sdk_ext_dir, relative_source)
             copy_or_link(source, target)
     for source in args.sdk_ext_files:
         common_prefix = os.path.commonprefix(args.sdk_ext_files)
         relative_source = os.path.relpath(source, common_prefix)
         target = os.path.join(sdk_ext_dir, relative_source)
         copy_or_link(source, target)
 
-    lib_path = os.path.join(target_dir, "lib")
     lib_mojom_path = os.path.join(lib_path, "mojom")
 
     # Copy generated mojom.dart files.
     generated_mojom_lib_path = os.path.join(args.gen_directory, "mojom/lib")
     for mojom_source_path in args.mojom_sources:
         path = mojom_path(mojom_source_path)
         source_path = '%s.dart' % os.path.join(generated_mojom_lib_path, path)
         target_path = '%s.dart' % os.path.join(lib_mojom_path, path)
         copy(source_path, target_path)
 
     # Symlink packages/
     package_path = os.path.join(args.package_root, args.package_name)
     link(lib_path, package_path)
 
     # Remove any broken symlinks in target_dir and package root.
     remove_broken_symlinks(target_dir)
     remove_broken_symlinks(args.package_root)
 
     # Write stamp file.
     with open(args.stamp_file, 'w'):
         pass
 
 if __name__ == '__main__':
     sys.exit(main())