history tail does not provide output

[gibiansky]

# Set up client
from jupyter_client import *
multimanager = MultiKernelManager()
manager = multimanager.get_kernel(multimanager.start_kernel("python3"))
client = manager.client()

# Add some history
client.execute("3 + 1")
client.execute("3 + 2")
client.execute("3 + 3")
client.get_shell_msg()
client.get_shell_msg()
client.get_shell_msg()

# get history
client.history(output=True, raw=True, hist_access_type="tail", n=3)
print(client.get_shell_msg())

outputs

{'buffers': [],
 'content': {u'history': [[401, 1, [u'3 + 3', None]],
   [401, 2, [u'3 + 4', None]],
   [401, 3, [u'3 + 5', None]]]},
 'header': {u'date': datetime.datetime(2016, 8, 1, 23, 48, 33, 745530),
  u'msg_id': u'c9a53f04-e669-4955-b0e8-ad88ec40855b',
  u'msg_type': u'history_reply',
  u'session': u'0f588569-25de-47f2-865a-0f77fbc84d51',
  u'username': u'silver',
  u'version': u'5.0'},
 'metadata': {},
 'msg_id': u'c9a53f04-e669-4955-b0e8-ad88ec40855b',
 'msg_type': u'history_reply',
 'parent_header': {u'date': datetime.datetime(2016, 8, 1, 23, 48, 33, 744099),
  u'msg_id': u'338254fe-74b2-4624-a199-8b79ec37dd4e',
  u'msg_type': u'history_request',
  u'session': u'089bcf7f-ac7b-4ba5-8268-14ac9c85ce0c',
  u'username': u'silver',
  u'version': u'5.0'}}

Note that there is no output in the history.

When I do something similar with a "range" query, I get output in some history items.

[gibiansky]

I see the same behaviour for search FYI

[minrk]

cc @takluyver if there's something funky we are doing in the history API handlers.

[takluyver]

tail uses the database directly, without a special case for the current session. IPython doesn't save output to the database by default (there's an option HistoryManager.db_log_output to enable it). range does have a special case for the current session, so it does show output from the current session.

As far as I know, none of our frontends send a history_request with output=True. We only use a small subset of the history messaging interface: tail requests with raw=True and output=False. It's probably another thing that we should simplify in a future version of the messaging protocol.