Add create_streams_if_needed().

zerver/lib/actions.py

@@ -805,6 +805,21 @@ def create_stream_if_needed(realm, stream_name, invite_only=False):
             send_event(event, active_user_ids(realm))
     return stream, created
 
+def create_streams_if_needed(realm, stream_names, invite_only):
+    # type: (Realm, List[text_type], bool) -> Tuple[List[Stream], List[Stream]]
+    added_streams = [] # type: List[Stream]
+    existing_streams = [] # type: List[Stream]
+    for stream_name in stream_names:
+        stream, created = create_stream_if_needed(realm,
+                                                  stream_name,
+                                                  invite_only=invite_only)
+        if created:
+            added_streams.append(stream)
+        else:
+            existing_streams.append(stream)
+
+    return added_streams, existing_streams
+
 def recipient_for_emails(emails, not_forged_mirror_message,
                          user_profile, sender):
     # type: (Iterable[text_type], bool, UserProfile, UserProfile) -> Recipient

zerver/tests/test_subs.py

@@ -35,7 +35,8 @@ from zerver.lib.actions import (
     do_create_realm, do_remove_default_stream, do_set_realm_create_stream_by_admins_only,
     gather_subscriptions_helper,
     gather_subscriptions, get_default_streams_for_realm, get_realm, get_stream,
-    get_user_profile_by_email, set_default_streams, get_subscription
+    get_user_profile_by_email, set_default_streams, get_subscription,
+    create_streams_if_needed
 )
 
 from zerver.views.streams import (
@@ -50,6 +51,31 @@ import six
 from six import text_type
 from six.moves import range, urllib
 
+class TestCreateStreams(ZulipTestCase):
+    def test_creating_streams(self):
+        # type: () -> None
+        stream_names = [u'new1', u'new2', u'new3']
+        realm = get_realm('zulip.com')
+
+        new_streams, existing_streams = create_streams_if_needed(
+            realm,
+            stream_names,
+            invite_only=True)
+        self.assertEqual(len(new_streams), 3)
+        self.assertEqual(len(existing_streams), 0)
+
+        actual_stream_names = {stream.name for stream in new_streams}
+        self.assertEqual(actual_stream_names, set(stream_names))
+
+        new_streams, existing_streams = create_streams_if_needed(
+            realm,
+            stream_names,
+            invite_only=True)
+        self.assertEqual(len(new_streams), 0)
+        self.assertEqual(len(existing_streams), 3)
+
+        actual_stream_names = {stream.name for stream in existing_streams}
+        self.assertEqual(actual_stream_names, set(stream_names))
 
 class StreamAdminTest(ZulipTestCase):
     def test_make_stream_public(self):