Document is_complete messages

Also, bump message spec version

IPython/core/release.py

@@ -40,7 +40,7 b' version = __version__ # backwards compatibility name'
 version_info = (_version_major, _version_minor, _version_patch, _version_extra)
 
 # Change this when incrementing the kernel protocol version
-kernel_protocol_version_info = (5, 0)
+kernel_protocol_version_info = (5, 1)
 kernel_protocol_version = "%i.%i" % kernel_protocol_version_info
 
 description = "IPython: Productive Interactive Computing"

docs/source/development/messaging.rst

@@ -9,7 +9,7 b' Versioning'
 ==========
 
 The IPython message specification is versioned independently of IPython.
-The current version of the specification is 5.0.
+The current version of the specification is 5.1.
 
 
 Introduction
@@ -573,6 +573,35 b' Message type: ``history_reply``::'
       'history' : list,
     }
 
+.. _msging_is_complete:
+
+Code completeness
+-----------------
+
+.. versionadded:: 5.1
+
+When the user enters a line in a console style interface, the console must
+decide whether to immediately execute the current code, or whether to show a
+continuation prompt for further input. For instance, in Python ``a = 5`` would
+be executed immediately, while ``for i in range(5):`` would expect further input.
+
+Frontends may have ways to override this, forcing the code to be sent for
+execution or forcing a continuation prompt. If the kernel does not reply promptly,
+the frontend will probably default to sending the code to be executed.
+
+Message type: ``is_complete_request``::
+
+    content = {
+        # The code entered so far as a multiline string
+        'code' : str,
+    }
+
+Message type: ``complete_reply``::
+
+    content = {
+        # True if the code is ready to execute, False if not
+        'complete' : bool,
+    }
 
 Connect
 -------

docs/source/development/wrapperkernels.rst

@@ -141,6 +141,17 b' relevant section of the :doc:`messaging spec <messaging>`.'
      
         :ref:`msging_history` messages
 
+   .. method:: do_is_complete(code)
+   
+     Is code entered in a console-like interface complete and ready to execute,
+     or should a continuation prompt be shown?
+     
+     :param str code: The code entered so far - possibly multiple lines
+     
+     .. seealso::
+     
+        :ref:`msging_is_complete` messages
+
    .. method:: do_shutdown(restart)
 
      Shutdown the kernel. You only need to handle your own clean up - the kernel