Factor out guts of '{topic,subscription}_name_from_path'.

Use a passed-in regex, in spite of Zawinski's law.

Put the factored-out code in 'gcloud._helpers', because I already know
I need it in logging.

Addresses:
#1580 (comment)
#1580 (comment)
#1580 (comment).

gcloud/_helpers.py

@@ -19,9 +19,10 @@
 import calendar
 import datetime
 import os
-from threading import local as Local
+import re
 import socket
 import sys
+from threading import local as Local
 
 from google.protobuf import timestamp_pb2
 import six
@@ -388,6 +389,43 @@ def _datetime_to_pb_timestamp(when):
     return timestamp_pb2.Timestamp(seconds=seconds, nanos=nanos)
 
 
+def _name_from_project_path(path, project, template):
+    """Validate a URI path and get the leaf object's name.
+
+    :type path: string
+    :param path: URI path containing the name.
+
+    :type project: string
+    :param project: The project associated with the request. It is
+                    included for validation purposes.
+
+    :type template: string
+    :param template: Template regex describing the expected form of the path.
+                     The regex must have two named groups, 'project' and
+                     'name'.
+
+    :rtype: string
+    :returns: Name parsed from ``path``.
+    :raises: :class:`ValueError` if the ``path`` is ill-formed or if
+             the project from the ``path`` does not agree with the
+             ``project`` passed in.
+    """
+    if isinstance(template, str):
+        template = re.compile(template)
+
+    match = template.match(path)
+
+    if not match:
+        raise ValueError('path did not match: %s' % (template.pattern))
+
+    found_project = match.group('project')
+    if found_project != project:
+        raise ValueError('Project from client should agree with '
+                         'project from resource.')
+
+    return match.group('name')
+
+
 try:
     from pytz import UTC  # pylint: disable=unused-import,wrong-import-order
 except ImportError:

gcloud/pubsub/_helpers.py

@@ -14,6 +14,14 @@
 
 """Helper functions for shared behavior."""
 
+import re
+
+from gcloud._helpers import _name_from_project_path
+
+
+_TOPIC_PATH_TEMPLATE = re.compile(
+    r'projects/(?P<project>\w+)/topics/(?P<name>\w+)')
+
 
 def topic_name_from_path(path, project):
     """Validate a topic URI path and get the topic name.
@@ -31,18 +39,11 @@ def topic_name_from_path(path, project):
              the project from the ``path`` does not agree with the
              ``project`` passed in.
     """
-    # PATH = 'projects/%s/topics/%s' % (PROJECT, TOPIC_NAME)
-    path_parts = path.split('/')
-    if (len(path_parts) != 4 or path_parts[0] != 'projects' or
-            path_parts[2] != 'topics'):
-        raise ValueError('Expected path to be of the form '
-                         'projects/{project}/topics/{topic_name}')
-    if (len(path_parts) != 4 or path_parts[0] != 'projects' or
-            path_parts[2] != 'topics' or path_parts[1] != project):
-        raise ValueError('Project from client should agree with '
-                         'project from resource.')
+    return _name_from_project_path(path, project, _TOPIC_PATH_TEMPLATE)
+
 
-    return path_parts[3]
+_SUBSCRIPTION_PATH_TEMPLATE = re.compile(
+    r'projects/(?P<project>\w+)/subscriptions/(?P<name>\w+)')
 
 
 def subscription_name_from_path(path, project):
@@ -61,16 +62,4 @@ def subscription_name_from_path(path, project):
              the project from the ``path`` does not agree with the
              ``project`` passed in.
     """
-    # PATH = 'projects/%s/subscriptions/%s' % (PROJECT, TOPIC_NAME)
-    path_parts = path.split('/')
-    if (len(path_parts) != 4 or path_parts[0] != 'projects' or
-            path_parts[2] != 'subscriptions'):
-        raise ValueError(
-            'Expected path to be of the form '
-            'projects/{project}/subscriptions/{subscription_name}')
-    if (len(path_parts) != 4 or path_parts[0] != 'projects' or
-            path_parts[2] != 'subscriptions' or path_parts[1] != project):
-        raise ValueError('Project from client should agree with '
-                         'project from resource.')
-
-    return path_parts[3]
+    return _name_from_project_path(path, project, _SUBSCRIPTION_PATH_TEMPLATE)

gcloud/pubsub/test__helpers.py

@@ -21,25 +21,7 @@ def _callFUT(self, path, project):
         from gcloud.pubsub._helpers import topic_name_from_path
         return topic_name_from_path(path, project)
 
-    def test_invalid_path_length(self):
-        PATH = 'projects/foo'
-        PROJECT = None
-        self.assertRaises(ValueError, self._callFUT, PATH, PROJECT)
-
-    def test_invalid_path_format(self):
-        TOPIC_NAME = 'TOPIC_NAME'
-        PROJECT = 'PROJECT'
-        PATH = 'foo/%s/bar/%s' % (PROJECT, TOPIC_NAME)
-        self.assertRaises(ValueError, self._callFUT, PATH, PROJECT)
-
-    def test_invalid_project(self):
-        TOPIC_NAME = 'TOPIC_NAME'
-        PROJECT1 = 'PROJECT1'
-        PROJECT2 = 'PROJECT2'
-        PATH = 'projects/%s/topics/%s' % (PROJECT1, TOPIC_NAME)
-        self.assertRaises(ValueError, self._callFUT, PATH, PROJECT2)
-
-    def test_valid_data(self):
+    def test_it(self):
         TOPIC_NAME = 'TOPIC_NAME'
         PROJECT = 'PROJECT'
         PATH = 'projects/%s/topics/%s' % (PROJECT, TOPIC_NAME)
@@ -53,25 +35,7 @@ def _callFUT(self, path, project):
         from gcloud.pubsub._helpers import subscription_name_from_path
         return subscription_name_from_path(path, project)
 
-    def test_invalid_path_length(self):
-        PATH = 'projects/foo'
-        PROJECT = None
-        self.assertRaises(ValueError, self._callFUT, PATH, PROJECT)
-
-    def test_invalid_path_format(self):
-        TOPIC_NAME = 'TOPIC_NAME'
-        PROJECT = 'PROJECT'
-        PATH = 'foo/%s/bar/%s' % (PROJECT, TOPIC_NAME)
-        self.assertRaises(ValueError, self._callFUT, PATH, PROJECT)
-
-    def test_invalid_project(self):
-        TOPIC_NAME = 'TOPIC_NAME'
-        PROJECT1 = 'PROJECT1'
-        PROJECT2 = 'PROJECT2'
-        PATH = 'projects/%s/subscriptions/%s' % (PROJECT1, TOPIC_NAME)
-        self.assertRaises(ValueError, self._callFUT, PATH, PROJECT2)
-
-    def test_valid_data(self):
+    def test_it(self):
         TOPIC_NAME = 'TOPIC_NAME'
         PROJECT = 'PROJECT'
         PATH = 'projects/%s/subscriptions/%s' % (PROJECT, TOPIC_NAME)

gcloud/test__helpers.py

@@ -526,6 +526,41 @@ def test_it(self):
         self.assertEqual(self._callFUT(dt_stamp), timestamp)
 
 
+class Test__name_from_project_path(unittest2.TestCase):
+
+    PROJECT = 'PROJECT'
+    THING_NAME = 'THING_NAME'
+    TEMPLATE = r'projects/(?P<project>\w+)/things/(?P<name>\w+)'
+
+    def _callFUT(self, path, project, template):
+        from gcloud._helpers import _name_from_project_path
+        return _name_from_project_path(path, project, template)
+
+    def test_w_invalid_path_length(self):
+        PATH = 'projects/foo'
+        with self.assertRaises(ValueError):
+            self._callFUT(PATH, None, self.TEMPLATE)
+
+    def test_w_invalid_path_segments(self):
+        PATH = 'foo/%s/bar/%s' % (self.PROJECT, self.THING_NAME)
+        with self.assertRaises(ValueError):
+            self._callFUT(PATH, self.PROJECT, self.TEMPLATE)
+
+    def test_w_mismatched_project(self):
+        PROJECT1 = 'PROJECT1'
+        PROJECT2 = 'PROJECT2'
+        PATH = 'projects/%s/things/%s' % (PROJECT1, self.THING_NAME)
+        with self.assertRaises(ValueError):
+            self._callFUT(PATH, PROJECT2, self.TEMPLATE)
+
+    def test_w_valid_data_w_compiled_regex(self):
+        import re
+        template = re.compile(self.TEMPLATE)
+        PATH = 'projects/%s/things/%s' % (self.PROJECT, self.THING_NAME)
+        name = self._callFUT(PATH, self.PROJECT, template)
+        self.assertEqual(name, self.THING_NAME)
+
+
 class _AppIdentity(object):
 
     def __init__(self, app_id):