Start of new callback system

IPython/core/callbacks.py

@@ -0,0 +1,57 b''
+from __future__ import print_function
+
+class CallbackManager(object):
+    def __init__(self, shell, available_callbacks):
+        self.shell = shell
+        self.callbacks = {n:[] for n in available_callbacks}
+    
+    def register(self, name, function):
+        if not callable(function):
+            raise TypeError('Need a callable, got %r' % function)
+        self.callbacks[name].append(function)
+    
+    def unregister(self, name, function):
+        self.callbacks[name].remove(function)
+    
+    def reset(self, name):
+        self.callbacks[name] = []
+    
+    def reset_all(self):
+        self.callbacks = {n:[] for n in self.callbacks}
+    
+    def fire(self, name, *args, **kwargs):
+        for func in self.callbacks[name]:
+            try:
+                func(*args, **kwargs)
+            except Exception:
+                print("Error in callback {} (for {}):".format(func, name))
+                self.shell.showtraceback()
+
+available_callbacks = {}
+def _collect(callback_proto):
+    available_callbacks[callback_proto.__name__] = callback_proto
+    return callback_proto
+
+@_collect
+def pre_execute():
+    """Fires before code is executed in response to user/frontend action.
+    
+    This includes comm and widget messages."""
+    pass
+
+@_collect
+def pre_execute_explicit():
+    """Fires before user-entered code runs."""
+    pass
+
+@_collect
+def post_execute():
+    """Fires after code is executed in response to user/frontend action.
+    
+    This includes comm and widget messages."""
+    pass
+
+@_collect
+def post_execute_explicit():
+    """Fires after user-entered code runs."""
+    pass
  No newline at end of file

IPython/core/interactiveshell.py

@@ -41,6 +41,7 b' from IPython.core import ultratb'
 from IPython.core.alias import AliasManager, AliasError
 from IPython.core.autocall import ExitAutocall
 from IPython.core.builtin_trap import BuiltinTrap
+from IPython.core.callbacks import CallbackManager, available_callbacks
 from IPython.core.compilerop import CachingCompiler, check_linecache_ipython
 from IPython.core.display_trap import DisplayTrap
 from IPython.core.displayhook import DisplayHook
@@ -467,6 +468,7 b' class InteractiveShell(SingletonConfigurable):'
 
         self.init_syntax_highlighting()
         self.init_hooks()
+        self.init_callbacks()
         self.init_pushd_popd_magic()
         # self.init_traceback_handlers use to be here, but we moved it below
         # because it and init_io have to come after init_readline.
@@ -827,12 +829,21 b' class InteractiveShell(SingletonConfigurable):'
 
         setattr(self.hooks,name, dp)
 
+    #-------------------------------------------------------------------------
+    # Things related to callbacks
+    #-------------------------------------------------------------------------
+
+    def init_callbacks(self):
+        self.callbacks = CallbackManager(self, available_callbacks)
+
     def register_post_execute(self, func):
-        """Register a function for calling after code execution.
+        """DEPRECATED: Use ip.callbacks.register('post_execute_explicit', func)
+        
+        Register a function for calling after code execution.
         """
-        if not callable(func):
-            raise ValueError('argument %s must be callable' % func)
-        self._post_execute[func] = True
+        warn("ip.register_post_execute is deprecated, use "
+             "ip.callbacks.register('post_execute_explicit', func) instead.")
+        self.callbacks.register('post_execute_explicit', func)
     
     #-------------------------------------------------------------------------
     # Things related to the "main" module
@@ -2649,6 +2660,10 b' class InteractiveShell(SingletonConfigurable):'
         if silent:
             store_history = False
 
+        self.callbacks.fire('pre_execute')
+        if not silent:
+            self.callbacks.fire('pre_execute_explicit')
+
         # If any of our input transformation (input_transformer_manager or
         # prefilter_manager) raises an exception, we store it in this variable
         # so that we can display the error after logging the input and storing
@@ -2717,28 +2732,10 b' class InteractiveShell(SingletonConfigurable):'
                 interactivity = "none" if silent else self.ast_node_interactivity
                 self.run_ast_nodes(code_ast.body, cell_name,
                                    interactivity=interactivity, compiler=compiler)
-
-                # Execute any registered post-execution functions.
-                # unless we are silent
-                post_exec = [] if silent else iteritems(self._post_execute)
-
-                for func, status in post_exec:
-                    if self.disable_failing_post_execute and not status:
-                        continue
-                    try:
-                        func()
-                    except KeyboardInterrupt:
-                        print("\nKeyboardInterrupt", file=io.stderr)
-                    except Exception:
-                        # register as failing:
-                        self._post_execute[func] = False
-                        self.showtraceback()
-                        print('\n'.join([
-                            "post-execution function %r produced an error." % func,
-                            "If this problem persists, you can disable failing post-exec functions with:",
-                            "",
-                            "    get_ipython().disable_failing_post_execute = True"
-                        ]), file=io.stderr)
+                
+                self.callbacks.fire('post_execute')
+                if not silent:
+                    self.callbacks.fire('post_execute_explicit')
 
         if store_history:
             # Write output to the database. Does nothing unless

IPython/core/tests/test_interactiveshell.py

@@ -27,6 +27,10 b' import shutil'
 import sys
 import tempfile
 import unittest
+try:
+    from unittest import mock
+except ImportError:
+    import mock
 from os.path import join
 
 # third-party
@@ -277,21 +281,32 b' class InteractiveShellTestCase(unittest.TestCase):'
         # ZeroDivisionError
         self.assertEqual(ip.var_expand(u"{1/0}"), u"{1/0}")
     
-    def test_silent_nopostexec(self):
-        """run_cell(silent=True) doesn't invoke post-exec funcs"""
-        d = dict(called=False)
-        def set_called():
-            d['called'] = True
+    def test_silent_postexec(self):
+        """run_cell(silent=True) doesn't invoke pre/post_execute_explicit callbacks"""
+        pre_explicit = mock.Mock()
+        pre_always = mock.Mock()
+        post_explicit = mock.Mock()
+        post_always = mock.Mock()
         
-        ip.register_post_execute(set_called)
-        ip.run_cell("1", silent=True)
-        self.assertFalse(d['called'])
-        # double-check that non-silent exec did what we expected
-        # silent to avoid
-        ip.run_cell("1")
-        self.assertTrue(d['called'])
-        # remove post-exec
-        ip._post_execute.pop(set_called)
+        ip.callbacks.register('pre_execute_explicit', pre_explicit)
+        ip.callbacks.register('pre_execute', pre_always)
+        ip.callbacks.register('post_execute_explicit', post_explicit)
+        ip.callbacks.register('post_execute', post_always)
+        
+        try:
+            ip.run_cell("1", silent=True)
+            assert pre_always.called
+            assert not pre_explicit.called
+            assert post_always.called
+            assert not post_explicit.called
+            # double-check that non-silent exec did what we expected
+            # silent to avoid
+            ip.run_cell("1")
+            assert pre_explicit.called
+            assert post_explicit.called
+        finally:
+            # remove post-exec
+            ip.callbacks.reset_all()
     
     def test_silent_noadvance(self):
         """run_cell(silent=True) doesn't advance execution_count"""

IPython/kernel/comm/comm.py

@@ -134,7 +134,9 b' class Comm(LoggingConfigurable):'
         """Handle a comm_msg message"""
         self.log.debug("handle_msg[%s](%s)", self.comm_id, msg)
         if self._msg_callback:
+            self.shell.callbacks.fire('pre_execute')
             self._msg_callback(msg)
+            self.shell.callbacks.fire('post_execute')
 
 
 __all__ = ['Comm']