Remove args/kwargs handling in TryNext.

This allows the error message in magic_paste to propagate correctly,
closing gh-1736.

IPython/core/error.py

@@ -1,66 +1,53 b''
 # encoding: utf-8
 """
 Global exception classes for IPython.core.
 
 Authors:
 
 * Brian Granger
 * Fernando Perez
 * Min Ragan-Kelley
 
 Notes
 -----
 """
 
 #-----------------------------------------------------------------------------
 #  Copyright (C) 2008-2011  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
 #-----------------------------------------------------------------------------
 
 #-----------------------------------------------------------------------------
 # Exception classes
 #-----------------------------------------------------------------------------
 
 class IPythonCoreError(Exception):
     pass
 
 
 class TryNext(IPythonCoreError):
     """Try next hook exception.
 
     Raise this in your hook function to indicate that the next hook handler
-    should be used to handle the operation.  If you pass arguments to the
-    constructor those arguments will be used by the next hook instead of the
-    original ones.
-    
-    A _msg argument will not be passed on, so it can be used as a displayable
-    error message.
+    should be used to handle the operation.
     """
 
-    def __init__(self, _msg="", *args, **kwargs):
-        self.args = args
-        self.kwargs = kwargs
-        self.msg = _msg
-    
-    def __str__(self):
-        return str(self.msg)
-
 class UsageError(IPythonCoreError):
     """Error in magic function arguments, etc.
 
     Something that probably won't warrant a full traceback, but should
     nevertheless interrupt a macro / batch file.
     """
 
 class StdinNotImplementedError(IPythonCoreError, NotImplementedError):
     """raw_input was requested in a context where it is not supported
 
     For use in IPython kernels, where only some frontends may support
     stdin requests.
     """

IPython/core/hooks.py

@@ -1,231 +1,229 b''
 """hooks for IPython.
 
 In Python, it is possible to overwrite any method of any object if you really
 want to.  But IPython exposes a few 'hooks', methods which are _designed_ to
 be overwritten by users for customization purposes.  This module defines the
 default versions of all such hooks, which get used by IPython if not
 overridden by the user.
 
 hooks are simple functions, but they should be declared with 'self' as their
 first argument, because when activated they are registered into IPython as
 instance methods.  The self argument will be the IPython running instance
 itself, so hooks have full access to the entire IPython object.
 
 If you wish to define a new hook and activate it, you need to put the
 necessary code into a python file which can be either imported or execfile()'d
 from within your profile's ipython_config.py configuration.
 
 For example, suppose that you have a module called 'myiphooks' in your
 PYTHONPATH, which contains the following definition:
 
 import os
 from IPython.core import ipapi
 ip = ipapi.get()
 
 def calljed(self,filename, linenum):
     "My editor hook calls the jed editor directly."
     print "Calling my own editor, jed ..."
     if os.system('jed +%d %s' % (linenum,filename)) != 0:
         raise TryNext()
 
 ip.set_hook('editor', calljed)
 
 You can then enable the functionality by doing 'import myiphooks'
 somewhere in your configuration files or ipython command line.
 """
 
 #*****************************************************************************
 #       Copyright (C) 2005 Fernando Perez. <[e-mail]>
 #
 #  Distributed under the terms of the BSD License.  The full license is in
 #  the file COPYING, distributed as part of this software.
 #*****************************************************************************
 
 import os, bisect
 import subprocess
 import sys
 
 from IPython.core.error import TryNext
 
 # List here all the default hooks.  For now it's just the editor functions
 # but over time we'll move here all the public API for user-accessible things.
 
 __all__ = ['editor', 'fix_error_editor', 'synchronize_with_editor',
            'input_prefilter', 'shutdown_hook', 'late_startup_hook',
            'show_in_pager','pre_prompt_hook',
            'pre_run_code_hook', 'clipboard_get']
 
 def editor(self, filename, linenum=None, wait=True):
     """Open the default editor at the given filename and linenumber.
 
     This is IPython's default editor hook, you can use it as an example to
     write your own modified one.  To set your own editor function as the
     new editor hook, call ip.set_hook('editor',yourfunc)."""
 
     # IPython configures a default editor at startup by reading $EDITOR from
     # the environment, and falling back on vi (unix) or notepad (win32).
     editor = self.editor
 
     # marker for at which line to open the file (for existing objects)
     if linenum is None or editor=='notepad':
         linemark = ''
     else:
         linemark = '+%d' % int(linenum)
 
     # Enclose in quotes if necessary and legal
     if ' ' in editor and os.path.isfile(editor) and editor[0] != '"':
         editor = '"%s"' % editor
 
     # Call the actual editor
     proc = subprocess.Popen('%s %s %s' % (editor, linemark, filename),
                             shell=True)
     if wait and proc.wait() != 0:
         raise TryNext()
 
 import tempfile
 def fix_error_editor(self,filename,linenum,column,msg):
     """Open the editor at the given filename, linenumber, column and
     show an error message. This is used for correcting syntax errors.
     The current implementation only has special support for the VIM editor,
     and falls back on the 'editor' hook if VIM is not used.
 
     Call ip.set_hook('fix_error_editor',youfunc) to use your own function,
     """
     def vim_quickfix_file():
         t = tempfile.NamedTemporaryFile()
         t.write('%s:%d:%d:%s\n' % (filename,linenum,column,msg))
         t.flush()
         return t
     if os.path.basename(self.editor) != 'vim':
         self.hooks.editor(filename,linenum)
         return
     t = vim_quickfix_file()
     try:
         if os.system('vim --cmd "set errorformat=%f:%l:%c:%m" -q ' + t.name):
             raise TryNext()
     finally:
         t.close()
 
 
 def synchronize_with_editor(self, filename, linenum, column):
         pass
 
 
 class CommandChainDispatcher:
     """ Dispatch calls to a chain of commands until some func can handle it
 
     Usage: instantiate, execute "add" to add commands (with optional
     priority), execute normally via f() calling mechanism.
 
     """
     def __init__(self,commands=None):
         if commands is None:
             self.chain = []
         else:
             self.chain = commands
 
 
     def __call__(self,*args, **kw):
         """ Command chain is called just like normal func.
 
         This will call all funcs in chain with the same args as were given to
         this function, and return the result of first func that didn't raise
         TryNext"""
-
+        last_exc = TryNext()
         for prio,cmd in self.chain:
             #print "prio",prio,"cmd",cmd #dbg
             try:
                 return cmd(*args, **kw)
-            except TryNext, exc:
-                if exc.args or exc.kwargs:
-                    args = exc.args
-                    kw = exc.kwargs
+            except TryNext as exc:
+                last_exc = exc
         # if no function will accept it, raise TryNext up to the caller
-        raise TryNext(*args, **kw)
+        raise last_exc
 
     def __str__(self):
         return str(self.chain)
 
     def add(self, func, priority=0):
         """ Add a func to the cmd chain with given priority """
         bisect.insort(self.chain,(priority,func))
 
     def __iter__(self):
         """ Return all objects in chain.
 
         Handy if the objects are not callable.
         """
         return iter(self.chain)
 
 
 def input_prefilter(self,line):
     """ Default input prefilter
 
     This returns the line as unchanged, so that the interpreter
     knows that nothing was done and proceeds with "classic" prefiltering
     (%magics, !shell commands etc.).
 
     Note that leading whitespace is not passed to this hook. Prefilter
     can't alter indentation.
 
     """
     #print "attempt to rewrite",line #dbg
     return line
 
 
 def shutdown_hook(self):
     """ default shutdown hook
 
     Typically, shotdown hooks should raise TryNext so all shutdown ops are done
     """
 
     #print "default shutdown hook ok" # dbg
     return
 
 
 def late_startup_hook(self):
     """ Executed after ipython has been constructed and configured
 
     """
     #print "default startup hook ok" # dbg
 
 
 def show_in_pager(self,s):
     """ Run a string through pager """
     # raising TryNext here will use the default paging functionality
     raise TryNext
 
 
 def pre_prompt_hook(self):
     """ Run before displaying the next prompt
 
     Use this e.g. to display output from asynchronous operations (in order
     to not mess up text entry)
     """
 
     return None
 
 
 def pre_run_code_hook(self):
     """ Executed before running the (prefiltered) code in IPython """
     return None
 
 
 def clipboard_get(self):
     """ Get text from the clipboard.
     """
     from IPython.lib.clipboard import (
         osx_clipboard_get, tkinter_clipboard_get,
         win32_clipboard_get
     )
     if sys.platform == 'win32':
         chain = [win32_clipboard_get, tkinter_clipboard_get]
     elif sys.platform == 'darwin':
         chain = [osx_clipboard_get, tkinter_clipboard_get]
     else:
         chain = [tkinter_clipboard_get]
     dispatcher = CommandChainDispatcher()
     for func in chain:
         dispatcher.add(func)
     text = dispatcher()
     return text

IPython/lib/clipboard.py

@@ -1,56 +1,54 b''
 """ Utilities for accessing the platform's clipboard.
 """
 
 import subprocess
 import sys
 
 from IPython.core.error import TryNext
 
 
 def win32_clipboard_get():
     """ Get the current clipboard's text on Windows.
 
     Requires Mark Hammond's pywin32 extensions.
     """
     try:
         import win32clipboard
     except ImportError:
-        message = ("Getting text from the clipboard requires the pywin32 "
-            "extensions: http://sourceforge.net/projects/pywin32/")
-        raise TryNext(_msg=message)
+        raise TryNext("Getting text from the clipboard requires the pywin32 "
+                      "extensions: http://sourceforge.net/projects/pywin32/")
     win32clipboard.OpenClipboard()
     text = win32clipboard.GetClipboardData(win32clipboard.CF_TEXT)
     # FIXME: convert \r\n to \n?
     win32clipboard.CloseClipboard()
     return text
 
 def osx_clipboard_get():
     """ Get the clipboard's text on OS X.
     """
     p = subprocess.Popen(['pbpaste', '-Prefer', 'ascii'],
         stdout=subprocess.PIPE)
     text, stderr = p.communicate()
     # Text comes in with old Mac \r line endings. Change them to \n.
     text = text.replace('\r', '\n')
     return text
 
 def tkinter_clipboard_get():
     """ Get the clipboard's text using Tkinter.
 
     This is the default on systems that are not Windows or OS X. It may
     interfere with other UI toolkits and should be replaced with an
     implementation that uses that toolkit.
     """
     try:
         import Tkinter
     except ImportError:
-        message = ("Getting text from the clipboard on this platform "
-            "requires Tkinter.")
-        raise TryNext(_msg=message)
+        raise TryNext("Getting text from the clipboard on this platform "
+                      "requires Tkinter.")
     root = Tkinter.Tk()
     root.withdraw()
     text = root.clipboard_get()
     root.destroy()
     return text
 
 

docs/source/whatsnew/development.txt

@@ -1,27 +1,35 b''
 =====================
  Development version
 =====================
 
 This document describes in-flight development work.
 
 Redesigned IPython notebook user interface
 ------------------------------------------
 
 .. add details
 
 Other new features
 ------------------
 
 * **%install_ext**: A new magic function to install an IPython extension from
   a URL. E.g. ``%install_ext https://bitbucket.org/birkenfeld/ipython-physics/raw/d1310a2ab15d/physics.py``.
 
 * The :envvar:`IPYTHON_DIR` environment variable, introduced in the Great
   Reorganization of 0.11 and existing only in versions 0.11-0.13, has been
   deprecated. As described in :ghissue:`1167`, the complexity and confusion of
   migrating to this variable is not worth the aesthetic improvement. Please use
   the historical :envvar:`IPYTHONDIR` environment variable instead.
 
 * The default value of *interactivity* passed from
   :meth:`~IPython.core.interactiveshell.InteractiveShell.run_cell` to
   :meth:`~IPython.core.interactiveshell.InteractiveShell.run_ast_nodes`
   is now configurable.
+
+Backwards incompatible changes
+------------------------------
+
+* The exception :exc:`IPython.core.error.TryNext` previously accepted
+  arguments and keyword arguments to be passed to the next implementation
+  of the hook. This feature was removed as it made error message propagation
+  difficult and violated the principle of loose coupling.