'recipes.py isolate' command to build an isolate of the current package's toolchain

recipes.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.
 
 """Tool to interact with recipe repositories.
 
 This tool operates on the nearest ancestor directory containing an
 infra/config/recipes.cfg.
 """
@@ skipping 200 matching lines @@
 
 def info(args):
   from recipe_engine import package
   repo_root, config_file = get_package_config(args)
   package_spec = package.PackageSpec.load_proto(config_file)
 
   if args.recipes_dir:
     print package_spec.recipes_path
 
 
+def isolate(package_deps, args):
+  from recipe_engine import package
+
+  repo_root, config_file = get_package_config(args)
+  context = package.PackageContext.from_proto_file(repo_root, config_file)
+  base_path = package_deps.root_package.recipes_dir
+  def norm(p):

[M-A Ruel, 2016/01/09 00:51:59]

I would have written it as:
norm = lambda *p: os.path.relpath(os.path.join(*p), base_path)

then line 229 becomes:
recipes_tool = norm(package_deps.get_package('recipe_engine').recipes_dir,
'recipes.py')

+    return os.path.relpath(p, base_path)
+  recipes_tool = norm(os.path.join(
+      package_deps.get_package('recipe_engine').recipes_dir,
+      'recipes.py'))
+  print json.dumps({
+    'variables': {
+      'files': [norm(f) for f in package_deps.root_package.all_files(context)],

[M-A Ruel, 2016/01/09 00:51:59]

sorted()

[luqui, 2016/01/15 23:11:27]

Done.

+      'command': [
+        'python',
+        recipes_tool,
+        '--package', norm(

[M-A Ruel, 2016/01/09 00:51:59]

put the norm()'ed item in a separate line.

[luqui, 2016/01/15 23:11:27]

Done.

+            package_deps.root_package.repo_spec.proto_file(context).path),
+        '--no-fetch',
+      ],
+    },
+  }, indent=2, separators=(',', ': '))

[M-A Ruel, 2016/01/09 00:51:59]

return 0
2 empty lines

[luqui, 2016/01/15 23:11:27]

Done.

+
 def main():
   from recipe_engine import package
 
   # Super-annoyingly, we need to manually parse for simulation_test since
   # argparse is bonkers and doesn't allow us to forward --help to subcommands.
   if 'simulation_test' in sys.argv:
     index = sys.argv.index('simulation_test')
     sys.argv = sys.argv[:index+1] + [json.dumps(sys.argv[index+1:])]
 
   parser = argparse.ArgumentParser(description='Do things with recipes.')
@@ skipping 77 matching lines @@
   doc_p.set_defaults(command='doc')
 
   info_p = subp.add_parser(
       'info',
       help='Query information about the current recipe package')
   info_p.set_defaults(command='info')
   info_p.add_argument(
       '--recipes-dir', action='store_true',
       help='Get the subpath where the recipes live relative to repository root')
 
+  isolate_p = subp.add_parser(
+      'isolate',
+      help='Write an isolate file to stdout for the recipe toolchain of the '
+           'current project')
+  isolate_p.set_defaults(command='isolate')
+
   args = parser.parse_args()
 
   if args.verbose:
     logging.getLogger().setLevel(logging.INFO)
 
   repo_root, config_file = get_package_config(args)
   package_deps = package.PackageDeps.create(
       repo_root, config_file, allow_fetch=not args.no_fetch,
       overrides=args.project_override)
 
   if args.command == 'fetch':
     # We already did everything in the create() call above.
     assert not args.no_fetch, 'Fetch? No-fetch? Make up your mind!'
     return 0
   if args.command == 'simulation_test':
     return simulation_test(package_deps, args)
   elif args.command == 'lint':
     return lint(package_deps, args)
   elif args.command == 'run':
     return run(package_deps, args)
   elif args.command == 'roll':
     assert not args.no_fetch, (
         'Rolling without fetching is not supported yet.')
     return roll(args)
   elif args.command == 'doc':
     return doc(package_deps, args)
   elif args.command == 'info':
     return info(args)
+  elif args.command == 'isolate':
+    return isolate(package_deps, args)
   else:
     print """Dear sir or madam,
         It has come to my attention that a quite impossible condition has come
     to pass in the specification you have issued a request for us to fulfill.
     It is with a heavy heart that I inform you that, at the present juncture,
     there is no conceivable next action to be taken upon your request, and as
     such, we have decided to abort the request with a nonzero status code.  We
     hope that your larger goals have not been put at risk due to this
     unfortunate circumstance, and wish you the best in deciding the next action
     in your venture and larger life.
 
     Warmly,
     recipes.py
     """
     return 1
 
   return 0
 
 if __name__ == '__main__':
   sys.exit(main())