slack_import: Support importing private slack channels.

templates/zerver/help/import-from-slack.md

@@ -85,8 +85,8 @@ root domain. Replace the last line above with the following, after replacing
   [Slack's documentation](https://get.slack.help/hc/en-us/articles/204897248-Guide-to-Slack-import-and-export-tools)
   for more details.
 
-- (Slack Plus import) Private channels and direct messages are currently
-  not imported. We expect to address this in a future revision.
+- (Slack Plus import) Direct messages are currently not imported. We
+  expect to address this in a future revision.
 
 - (Slack Plus import) Message edit history is currently not imported.
 

zerver/data_import/slack.py

@@ -347,7 +347,7 @@ def channels_to_zerver_stream(slack_data_dir: str, realm_id: int, added_users: A
 
     stream_id_count = subscription_id_count = recipient_id_count = defaultstream_id = 0
 
-    def process_channels(channels: List[Dict[str, Any]]) -> None:
+    def process_channels(channels: List[Dict[str, Any]], invite_only: bool=False) -> None:
         nonlocal stream_id_count
         nonlocal recipient_id_count
         nonlocal defaultstream_id
@@ -365,7 +365,7 @@ def process_channels(channels: List[Dict[str, Any]]) -> None:
 
             # construct the stream object and append it to zerver_stream
             stream = build_stream(float(channel["created"]), realm_id, channel["name"],
-                                  description, stream_id, channel["is_archived"])
+                                  description, stream_id, channel["is_archived"], invite_only)
             zerver_stream.append(stream)
 
             # construct defaultstream object
@@ -411,8 +411,14 @@ def process_channels(channels: List[Dict[str, Any]]) -> None:
             #         }
             #         ],
 
-    channels = get_data_file(slack_data_dir + '/channels.json')
-    process_channels(channels)
+    public_channels = get_data_file(slack_data_dir + '/channels.json')
+    process_channels(public_channels)
+
+    try:
+        private_channels = get_data_file(slack_data_dir + '/groups.json')
+    except FileNotFoundError:
+        private_channels = []
+    process_channels(private_channels, True)
 
     for user in zerver_userprofile:
         # this maps the recipients and subscriptions

zerver/tests/test_slack_importer.py

@@ -280,7 +280,7 @@ def test_channels_to_zerver_stream(self, mock_get_data_file: mock.Mock) -> None:
                         {'id': "C061A0HJG", 'name': 'feedback', 'created': '1433558359',
                          'is_general': False, 'members': ['U061A3E0G'], 'is_archived': False,
                          'topic': {'value': ''}, 'purpose': {'value': ''}}]
-        mock_get_data_file.return_value = channel_data
+        mock_get_data_file.side_effect = [channel_data, []]
 
         channel_to_zerver_stream_output = channels_to_zerver_stream('./random_path', realm_id, added_users,
                                                                     zerver_userprofile)