Show invalid config message on TraitErrors during initialization

implemented via @catch_config decorator

Now, the event that was triggered by invalid app config (see `--log-level 5`) is triggered by bad config at any point during initialization.

This *will* catch TraitError bugs in IPython itself, but only during initialization.

closes gh-908

IPython/config/application.py

@@ -26,6 +26,8 b' import sys'
 from copy import deepcopy
 from collections import defaultdict
 
+from IPython.external.decorator import decorator
+
 from IPython.config.configurable import SingletonConfigurable
 from IPython.config.loader import (
     KVArgParseConfigLoader, PyFileConfigLoader, Config, ArgumentError, ConfigFileNotFound,
@@ -69,6 +71,26 b" subcommand 'cmd', do: `{app} cmd -h`."
 # Application class
 #-----------------------------------------------------------------------------
 
+@decorator
+def catch_config(method, app, *args, **kwargs):
+    """Method decorator for catching invalid config (Trait/ArgumentErrors) during init.
+
+    On a TraitError (generally caused by bad config), this will print the trait's
+    message, and exit the app.
+    
+    For use on init methods, to prevent invoking excepthook on invalid input.
+    """
+    try:
+        return method(app, *args, **kwargs)
+    except (TraitError, ArgumentError) as e:
+        app.print_description()
+        app.print_help()
+        app.print_examples()
+        app.log.fatal("Bad config encountered during initialization:")
+        app.log.fatal(str(e))
+        app.log.debug("Config at the time: %s", app.config)
+        app.exit(1)
+
 
 class ApplicationError(Exception):
     pass
@@ -173,6 +195,7 b' class Application(SingletonConfigurable):'
         self._log_handler.setFormatter(self._log_formatter)
         self.log.addHandler(self._log_handler)
 
+    @catch_config
     def initialize(self, argv=None):
         """Do the basic steps to configure me.
 
@@ -317,6 +340,7 b' class Application(SingletonConfigurable):'
         # events.
         self.config = newconfig
 
+    @catch_config
     def initialize_subcommand(self, subc, argv=None):
         """Initialize a subcommand with argv."""
         subapp,help = self.subcommands.get(subc)
@@ -376,6 +400,7 b' class Application(SingletonConfigurable):'
             flags[key] = (newflag, help)
         return flags, aliases
 
+    @catch_config
     def parse_command_line(self, argv=None):
         """Parse the command line arguments."""
         argv = sys.argv[1:] if argv is None else argv
@@ -402,18 +427,12 b' class Application(SingletonConfigurable):'
 
         loader = KVArgParseConfigLoader(argv=argv, aliases=aliases,
                                         flags=flags)
-        try:
-            config = loader.load_config()
-            self.update_config(config)
-        except (TraitError, ArgumentError) as e:
-            self.print_description()
-            self.print_help()
-            self.print_examples()
-            self.log.fatal(str(e))
-            self.exit(1)
+        config = loader.load_config()
+        self.update_config(config)
         # store unparsed args in extra_args
         self.extra_args = loader.extra_args
 
+    @catch_config
     def load_config_file(self, filename, path=None):
         """Load a .py based config file by filename and path."""
         loader = PyFileConfigLoader(filename, path=path)

IPython/core/application.py

@@ -34,7 +34,7 b' import os'
 import shutil
 import sys
 
-from IPython.config.application import Application
+from IPython.config.application import Application, catch_config
 from IPython.config.configurable import Configurable
 from IPython.config.loader import Config, ConfigFileNotFound
 from IPython.core import release, crashhandler
@@ -304,7 +304,7 b' class BaseIPythonApplication(Application):'
             with open(fname, 'w') as f:
                 f.write(s)
 
-
+    @catch_config
     def initialize(self, argv=None):
         # don't hook up crash handler before parsing command-line
         self.parse_command_line(argv)

IPython/frontend/html/notebook/notebookapp.py

@@ -43,6 +43,7 b' from .handlers import (LoginHandler,'
 )
 from .notebookmanager import NotebookManager
 
+from IPython.config.application import catch_config
 from IPython.core.application import BaseIPythonApplication
 from IPython.core.profiledir import ProfileDir
 from IPython.zmq.session import Session, default_secure
@@ -260,6 +261,7 b' class NotebookApp(BaseIPythonApplication):'
         # and all of its ancenstors until propagate is set to False.
         self.log.propagate = False
 
+    @catch_config
     def initialize(self, argv=None):
         super(NotebookApp, self).initialize(argv)
         self.init_configurables()

IPython/frontend/qt/console/qtconsoleapp.py

@@ -29,7 +29,7 b' import uuid'
 from IPython.external.qt import QtGui
 
 # Local imports
-from IPython.config.application import boolean_flag
+from IPython.config.application import boolean_flag, catch_config
 from IPython.core.application import BaseIPythonApplication
 from IPython.core.profiledir import ProfileDir
 from IPython.lib.kernel import tunnel_to_kernel, find_connection_file
@@ -516,6 +516,7 b' class IPythonQtConsoleApp(BaseIPythonApplication):'
             else:
                 raise IOError("Stylesheet %r not found."%self.stylesheet)
 
+    @catch_config
     def initialize(self, argv=None):
         super(IPythonQtConsoleApp, self).initialize(argv)
         self.init_connection_file()

IPython/frontend/terminal/ipapp.py

@@ -32,7 +32,7 b' import sys'
 from IPython.config.loader import (
     Config, PyFileConfigLoader, ConfigFileNotFound
 )
-from IPython.config.application import boolean_flag
+from IPython.config.application import boolean_flag, catch_config
 from IPython.core import release
 from IPython.core import usage
 from IPython.core.completer import Completer
@@ -285,7 +285,8 b' class TerminalIPythonApp(BaseIPythonApplication, InteractiveShellApp):'
             argv[idx] = sub
 
         return super(TerminalIPythonApp, self).parse_command_line(argv)
-
+    
+    @catch_config
     def initialize(self, argv=None):
         """Do actions after construct, but before starting the app."""
         super(TerminalIPythonApp, self).initialize(argv)

IPython/parallel/apps/baseapp.py

@@ -29,6 +29,7 b' import sys'
 
 from subprocess import Popen, PIPE
 
+from IPython.config.application import catch_config
 from IPython.core import release
 from IPython.core.crashhandler import CrashHandler
 from IPython.core.application import (
@@ -144,6 +145,7 b' class BaseParallelApplication(BaseIPythonApplication):'
     aliases = Dict(base_aliases)
     flags = Dict(base_flags)
     
+    @catch_config
     def initialize(self, argv=None):
         """initialize the app"""
         super(BaseParallelApplication, self).initialize(argv)

IPython/parallel/apps/ipclusterapp.py

@@ -31,7 +31,7 b' from subprocess import check_call, CalledProcessError, PIPE'
 import zmq
 from zmq.eventloop import ioloop
 
-from IPython.config.application import Application, boolean_flag
+from IPython.config.application import Application, boolean_flag, catch_config
 from IPython.config.loader import Config
 from IPython.core.application import BaseIPythonApplication
 from IPython.core.profiledir import ProfileDir
@@ -269,6 +269,7 b' class IPClusterEngines(BaseParallelApplication):'
     flags = Dict(engine_flags)
     _stopping = False
 
+    @catch_config
     def initialize(self, argv=None):
         super(IPClusterEngines, self).initialize(argv)
         self.init_signal()

IPython/parallel/apps/ipcontrollerapp.py

@@ -41,9 +41,10 b' from IPython.parallel.apps.baseapp import ('
     BaseParallelApplication,
     base_aliases,
     base_flags,
+    catch_config,
 )
 from IPython.utils.importstring import import_item
-from IPython.utils.traitlets import Instance, Unicode, Bool, List, Dict
+from IPython.utils.traitlets import Instance, Unicode, Bool, List, Dict, TraitError
 
 from IPython.zmq.session import (
     Session, session_aliases, session_flags, default_secure
@@ -263,7 +264,9 b' class IPControllerApp(BaseParallelApplication):'
             self.factory = HubFactory(config=c, log=self.log)
             # self.start_logging()
             self.factory.init_hub()
-        except:
+        except TraitError:
+            raise
+        except Exception:
             self.log.error("Couldn't construct the Controller", exc_info=True)
             self.exit(1)
         
@@ -385,6 +388,7 b' class IPControllerApp(BaseParallelApplication):'
             self.log.addHandler(handler)
             self._log_handler = handler
     
+    @catch_config
     def initialize(self, argv=None):
         super(IPControllerApp, self).initialize(argv)
         self.forward_logging()

IPython/parallel/apps/ipengineapp.py

@@ -34,6 +34,7 b' from IPython.parallel.apps.baseapp import ('
     BaseParallelApplication,
     base_aliases,
     base_flags,
+    catch_config,
 )
 from IPython.zmq.log import EnginePUBHandler
 from IPython.zmq.session import (
@@ -318,6 +319,7 b' class IPEngineApp(BaseParallelApplication):'
         else:
             mpi = None
 
+    @catch_config
     def initialize(self, argv=None):
         super(IPEngineApp, self).initialize(argv)
         self.init_mpi()

IPython/parallel/apps/iploggerapp.py

@@ -30,7 +30,8 b' from IPython.utils.traitlets import Bool, Dict, Unicode'
 
 from IPython.parallel.apps.baseapp import (
     BaseParallelApplication,
-    base_aliases
+    base_aliases,
+    catch_config,
 )
 from IPython.parallel.apps.logwatcher import LogWatcher
 
@@ -68,6 +69,7 b' class IPLoggerApp(BaseParallelApplication):'
     classes = [LogWatcher, ProfileDir]
     aliases = Dict(aliases)
 
+    @catch_config
     def initialize(self, argv=None):
         super(IPLoggerApp, self).initialize(argv)
         self.init_watcher()

IPython/zmq/ipkernel.py

@@ -28,7 +28,7 b' import zmq'
 
 # Local imports.
 from IPython.config.configurable import Configurable
-from IPython.config.application import boolean_flag
+from IPython.config.application import boolean_flag, catch_config
 from IPython.core.application import ProfileDir
 from IPython.core.error import StdinNotImplementedError
 from IPython.core.shellapp import (
@@ -730,6 +730,8 b' class IPKernelApp(KernelApp, InteractiveShellApp):'
         selecting a particular matplotlib backend and loop integration.
         """
     )
+    
+    @catch_config
     def initialize(self, argv=None):
         super(IPKernelApp, self).initialize(argv)
         self.init_shell()

IPython/zmq/kernelapp.py

@@ -26,7 +26,7 b' import zmq'
 # IPython imports.
 from IPython.core.ultratb import FormattedTB
 from IPython.core.application import (
-    BaseIPythonApplication, base_flags, base_aliases
+    BaseIPythonApplication, base_flags, base_aliases, catch_config
 )
 from IPython.utils import io
 from IPython.utils.localinterfaces import LOCALHOST
@@ -275,6 +275,7 b' class KernelApp(BaseIPythonApplication):'
         )
         self.kernel.record_ports(self.ports)
 
+    @catch_config
     def initialize(self, argv=None):
         super(KernelApp, self).initialize(argv)
         self.init_blackhole()