Add Paths as first-class types in configs.

scripts/slave/unittests/recipes_test.py

Index: scripts/slave/unittests/recipes_test.py
diff --git a/scripts/slave/unittests/recipes_test.py b/scripts/slave/unittests/recipes_test.py
index eec7801c26b12ba477d160a40b07adbed7c11ab6..5a319a569683f7877044a7e965534ef5407395dd 100755
--- a/scripts/slave/unittests/recipes_test.py
+++ b/scripts/slave/unittests/recipes_test.py
@@ -52,6 +52,7 @@ import unittest
 
 from common import annotator
 from slave import recipe_util
+from slave import recipe_config_types
 from slave import annotated_run
 from slave import recipe_loader
 
@@ -114,6 +115,7 @@ def execute_test_case(test_data, recipe_path, recipe_name):
       return recipe_loader.CreateRecipeApi(test_data=test_data, *args, **kwargs)
 
     with cover():
+      recipe_config_types.ResetTostringFns()
       step_data = annotated_run.run_steps(
         stream, props, props, api, test_data).steps_ran.values()
       return [s.step for s in step_data]
@@ -131,7 +133,8 @@ def train_from_tests((recipe_path, recipe_name)):
     expected_path = expected_for(recipe_path, test_data.name)
     print 'Writing', expected_path
     with open(expected_path, 'wb') as f:
-      json.dump(steps, f, sort_keys=True, indent=2, separators=(',', ': '))
+      json.dump(steps, f, sort_keys=True, indent=2, separators=(',', ': '),
+                default=recipe_config_types.json_fixup)
 
   return True
 
@@ -148,7 +151,8 @@ def load_tests(loader, _standard_tests, _pattern):
             def test_(self):
               steps = execute_test_case(test_data, recipe_path, recipe_name)
               # Roundtrip json to get same string encoding as load
-              steps = json.loads(json.dumps(steps))
+              steps = json.loads(
+                json.dumps(steps, default=recipe_config_types.json_fixup))
               with open(expected_path, 'rb') as f:
                 expected = json.load(f)
               self.assertEqual(steps, expected)