Add Paths as first-class types in configs.

scripts/slave/recipe_modules/path/config.py

Index: scripts/slave/recipe_modules/path/config.py
diff --git a/scripts/slave/recipe_modules/path/config.py b/scripts/slave/recipe_modules/path/config.py
new file mode 100644
index 0000000000000000000000000000000000000000..cb1a3706f0c1ac7c7582ef959ceadbf11b67fe21
--- /dev/null
+++ b/scripts/slave/recipe_modules/path/config.py
@@ -0,0 +1,46 @@
+# Copyright 2013 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.
+
+from slave.recipe_config import config_item_context, ConfigGroup, Dict, Static
+from slave.recipe_config_types import Path
+
+def BaseConfig(CURRENT_WORKING_DIR, **_kwargs):
+  assert CURRENT_WORKING_DIR[0].endswith(('\\', '/'))
+  return ConfigGroup(
+    # base path name -> [tokenized absolute path]
+    base_paths    = Dict(value_type=tuple),
+
+    # dynamic path name -> Path object (referencing one of the base_paths)
+    dynamic_paths = Dict(value_type=(Path, type(None))),
+
+    CURRENT_WORKING_DIR = Static(tuple(CURRENT_WORKING_DIR)),
+  )
+
+VAR_TEST_MAP = {
+  'CURRENT_WORKING_DIR': (
+    ['/', 'b', 'build', 'slave', 'fake_slave', 'build'],
+    ['E:\\', 'build', 'slave', 'fake_slave', 'build'],
+  ),
+}
+
+def test_name(args):
+  if args['CURRENT_WORKING_DIR'][0] == '/':
+    return 'posix'
+  else:
+    return 'windows'
+
+config_ctx = config_item_context(BaseConfig, VAR_TEST_MAP, test_name)
+
+@config_ctx(is_root=True)
+def BASE(c):
+  c.base_paths['cwd'] = c.CURRENT_WORKING_DIR
+
+@config_ctx()
+def buildbot(c):
+  c.base_paths['root'] = c.CURRENT_WORKING_DIR[:-4]
+  c.base_paths['slave_build'] = c.CURRENT_WORKING_DIR
+  for token in ('build_internal', 'build', 'depot_tools'):
+    c.base_paths[token] = c.base_paths['root'] + (token,)
+  c.dynamic_paths['checkout'] = None
+