send idle/busy on all shell messages

Instead of just those that execute code.
This means that kernel_info_request triggers busy/idle,
allowing clients to check IOPub channel status without executing code.

IPython/kernel/comm/manager.py

@@ -1,15 +1,7 b''
 """Base class to manage comms"""
 
-#-----------------------------------------------------------------------------
-#  Copyright (C) 2013  The IPython Development Team
-#
-#  Distributed under the terms of the BSD License.  The full license is in
-#  the file COPYING, distributed as part of this software.
-#-----------------------------------------------------------------------------
-
-#-----------------------------------------------------------------------------
-# Imports
-#-----------------------------------------------------------------------------
+# Copyright (c) IPython Development Team.
+# Distributed under the terms of the Modified BSD License.
 
 import sys
 
@@ -23,9 +15,6 b' from IPython.utils.traitlets import Instance, Unicode, Dict, Any'
 
 from .comm import Comm
 
-#-----------------------------------------------------------------------------
-# Code
-#-----------------------------------------------------------------------------
 
 def lazy_keys(dikt):
     """Return lazy-evaluated string representation of a dictionary's keys
@@ -36,27 +25,6 b' def lazy_keys(dikt):'
     return LazyEvaluate(lambda d: list(d.keys()))
 
 
-def with_output(method):
-    """method decorator for ensuring output is handled properly in a message handler
-    
-    - sets parent header before entering the method
-    - publishes busy/idle
-    - flushes stdout/stderr after
-    """
-    def method_with_output(self, stream, ident, msg):
-        parent = msg['header']
-        self.shell.set_parent(parent)
-        self.shell.kernel._publish_status('busy', parent)
-        try:
-            return method(self, stream, ident, msg)
-        finally:
-            sys.stdout.flush()
-            sys.stderr.flush()
-            self.shell.kernel._publish_status('idle', parent)
-    
-    return method_with_output
-
-
 class CommManager(LoggingConfigurable):
     """Manager for Comms in the Kernel"""
     
@@ -127,7 +95,6 b' class CommManager(LoggingConfigurable):'
         return comm
     
     # Message handlers
-    @with_output
     def comm_open(self, stream, ident, msg):
         """Handler for comm_open messages"""
         content = msg['content']
@@ -151,7 +118,6 b' class CommManager(LoggingConfigurable):'
             comm.close()
             self.unregister_comm(comm_id)
     
-    @with_output
     def comm_msg(self, stream, ident, msg):
         """Handler for comm_msg messages"""
         content = msg['content']
@@ -165,7 +131,6 b' class CommManager(LoggingConfigurable):'
         except Exception:
             self.log.error("Exception in comm_msg for %s", comm_id, exc_info=True)
     
-    @with_output
     def comm_close(self, stream, ident, msg):
         """Handler for comm_close messages"""
         content = msg['content']

IPython/kernel/zmq/kernelbase.py

@@ -162,6 +162,10 b' class Kernel(Configurable):'
             self.log.error("Invalid Message", exc_info=True)
             return
 
+        # Set the parent message for side effects.
+        self.set_parent(idents, msg)
+        self._publish_status(u'busy')
+        
         header = msg['header']
         msg_id = header['msg_id']
         msg_type = msg['header']['msg_type']
@@ -197,6 +201,10 b' class Kernel(Configurable):'
             finally:
                 signal(SIGINT, sig)
     
+        sys.stdout.flush()
+        sys.stderr.flush()
+        self._publish_status(u'idle')
+    
     def enter_eventloop(self):
         """enter eventloop"""
         self.log.info("entering eventloop %s", self.eventloop)
@@ -281,7 +289,7 b' class Kernel(Configurable):'
         self.session.send(self.iopub_socket,
                           u'status',
                           {u'execution_state': status},
-                          parent=parent,
+                          parent=parent or self._parent_header,
                           ident=self._topic('status'),
                           )
     
@@ -313,8 +321,6 b' class Kernel(Configurable):'
     def execute_request(self, stream, ident, parent):
         """handle an execute_request"""
         
-        self._publish_status(u'busy', parent)
-        
         try:
             content = parent[u'content']
             code = py3compat.cast_unicode_py2(content[u'code'])
@@ -329,9 +335,6 b' class Kernel(Configurable):'
         
         md = self._make_metadata(parent['metadata'])
         
-        # Set the parent message of the display hook and out streams.
-        self.set_parent(ident, parent)
-        
         # Re-broadcast our input for the benefit of listening clients, and
         # start computing output
         if not silent:
@@ -367,8 +370,6 b' class Kernel(Configurable):'
         if not silent and reply_msg['content']['status'] == u'error':
             self._abort_queues()
 
-        self._publish_status(u'idle', parent)
-
     def do_execute(self, code, silent, store_history=True,
                    user_experssions=None, allow_stdin=False):
         """Execute user code. Must be overridden by subclasses.
@@ -484,11 +485,6 b' class Kernel(Configurable):'
             self.log.error("Got bad msg: %s", parent, exc_info=True)
             return
 
-        self._publish_status(u'busy', parent)
-
-        # Set the parent message of the display hook and out streams.
-        self.set_parent(ident, parent)
-
         md = self._make_metadata(parent['metadata'])
 
         reply_content, result_buf = self.do_apply(content, bufs, msg_id, md)
@@ -503,8 +499,6 b' class Kernel(Configurable):'
         self.session.send(stream, u'apply_reply', reply_content,
                     parent=parent, ident=ident,buffers=result_buf, metadata=md)
 
-        self._publish_status(u'idle', parent)
-
     def do_apply(self, content, bufs, msg_id, reply_metadata):
         """Override in subclasses to support the IPython parallel framework.
         """

docs/source/development/messaging.rst

@@ -886,12 +886,17 b' This message type is used by frontends to monitor the status of the kernel.'
 Message type: ``status``::
 
     content = {
-        # When the kernel starts to execute code, it will enter the 'busy'
+        # When the kernel starts to handle a message, it will enter the 'busy'
         # state and when it finishes, it will enter the 'idle' state.
         # The kernel will publish state 'starting' exactly once at process startup.
         execution_state : ('busy', 'idle', 'starting')
     }
 
+.. versionchanged:: 5.0
+
+    Busy and idle messages should be sent before/after handling every shell message,
+    not just execution.
+
 Clear output
 ------------