Isolate better traceback printing

IPython/frontend/prefilterfrontend.py

@@ -1,248 +1,251 b''
 """
 Frontend class that uses IPython0 to prefilter the inputs.
 
 Using the IPython0 mechanism gives us access to the magics.
 
 This is a transitory class, used here to do the transition between
 ipython0 and ipython1. This class is meant to be short-lived as more
 functionnality is abstracted out of ipython0 in reusable functions and
 is added on the interpreter. This class can be a used to guide this
 refactoring.
 """
 __docformat__ = "restructuredtext en"
 
 #-------------------------------------------------------------------------------
 #  Copyright (C) 2008  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
 #-------------------------------------------------------------------------------
 import sys
 
 from linefrontendbase import LineFrontEndBase, common_prefix
 from frontendbase import FrontEndBase
 
 from IPython.ipmaker import make_IPython
 from IPython.ipapi import IPApi
 from IPython.kernel.core.redirector_output_trap import RedirectorOutputTrap
 
 from IPython.kernel.core.sync_traceback_trap import SyncTracebackTrap
 
 from IPython.genutils import Term
 import pydoc
 import os
 import sys
 
 
 def mk_system_call(system_call_function, command):
     """ given a os.system replacement, and a leading string command,
         returns a function that will execute the command with the given
         argument string.
     """
     def my_system_call(args):
         system_call_function("%s %s" % (command, args))
 
     my_system_call.__doc__ = "Calls %s" % command
     return my_system_call
 
 #-------------------------------------------------------------------------------
 # Frontend class using ipython0 to do the prefiltering. 
 #-------------------------------------------------------------------------------
 class PrefilterFrontEnd(LineFrontEndBase):
     """ Class that uses ipython0 to do prefilter the input, do the
     completion and the magics.
 
     The core trick is to use an ipython0 instance to prefilter the
     input, and share the namespace between the interpreter instance used
     to execute the statements and the ipython0 used for code
     completion...
     """
 
     debug = False
     
     def __init__(self, ipython0=None, *args, **kwargs):
         """ Parameters:
             -----------
 
             ipython0: an optional ipython0 instance to use for command
             prefiltering and completion.
         """
         LineFrontEndBase.__init__(self, *args, **kwargs)
         self.shell.output_trap = RedirectorOutputTrap(
                             out_callback=self.write,
                             err_callback=self.write,
                                             )
         self.shell.traceback_trap = SyncTracebackTrap(
                         formatters=self.shell.traceback_trap.formatters,
                             )
 
         # Start the ipython0 instance:
         self.save_output_hooks()
         if ipython0 is None:
             # Instanciate an IPython0 interpreter to be able to use the
             # prefiltering.
             # XXX: argv=[] is a bit bold.
             ipython0 = make_IPython(argv=[], 
                                     user_ns=self.shell.user_ns,
                                     user_global_ns=self.shell.user_global_ns)
         self.ipython0 = ipython0
         # Set the pager:
         self.ipython0.set_hook('show_in_pager', 
                     lambda s, string: self.write("\n" + string))
         self.ipython0.write = self.write
         self._ip = _ip = IPApi(self.ipython0)
         # Make sure the raw system call doesn't get called, as we don't
         # have a stdin accessible.
         self._ip.system = self.system_call
         # XXX: Muck around with magics so that they work better
         # in our environment
         self.ipython0.magic_ls = mk_system_call(self.system_call, 
                                                             'ls -CF')
         # And now clean up the mess created by ipython0
         self.release_output()
 
 
         if not 'banner' in kwargs and self.banner is None:
             self.banner = self.ipython0.BANNER + """
 This is the wx frontend, by Gael Varoquaux. This is EXPERIMENTAL code."""
 
         self.start()
 
     #--------------------------------------------------------------------------
     # FrontEndBase interface 
     #--------------------------------------------------------------------------
 
     def show_traceback(self):
         """ Use ipython0 to capture the last traceback and display it.
         """
-        self.capture_output()
+        # Don't do the capture; the except_hook has already done some
+        # modifications to the IO streams, if we store them, we'll be
+        # storing the wrong ones.
+        #self.capture_output()
         self.ipython0.showtraceback(tb_offset=-1)
         self.release_output()
 
 
     def execute(self, python_string, raw_string=None):
         if self.debug:
             print 'Executing Python code:', repr(python_string)
         self.capture_output()
         LineFrontEndBase.execute(self, python_string,
                                     raw_string=raw_string)
         self.release_output()
 
 
     def save_output_hooks(self):
         """ Store all the output hooks we can think of, to be able to
         restore them. 
         
         We need to do this early, as starting the ipython0 instance will
         screw ouput hooks.
         """
         self.__old_cout_write = Term.cout.write
         self.__old_cerr_write = Term.cerr.write
         self.__old_stdout = sys.stdout
         self.__old_stderr= sys.stderr
         self.__old_help_output = pydoc.help.output
         self.__old_display_hook = sys.displayhook
 
 
     def capture_output(self):
         """ Capture all the output mechanisms we can think of.
         """
         self.save_output_hooks()
         Term.cout.write = self.write
         Term.cerr.write = self.write
         sys.stdout = Term.cout
         sys.stderr = Term.cerr
         pydoc.help.output = self.shell.output_trap.out
 
 
     def release_output(self):
         """ Release all the different captures we have made.
         """
         Term.cout.write = self.__old_cout_write
         Term.cerr.write = self.__old_cerr_write
         sys.stdout = self.__old_stdout
         sys.stderr = self.__old_stderr
         pydoc.help.output = self.__old_help_output 
         sys.displayhook = self.__old_display_hook 
 
 
     def complete(self, line):
         # FIXME: This should be factored out in the linefrontendbase
         # method.
         word = line.split('\n')[-1].split(' ')[-1]
         completions = self.ipython0.complete(word)
         # FIXME: The proper sort should be done in the complete method.
         key = lambda x: x.replace('_', '')
         completions.sort(key=key)
         if completions:
             prefix = common_prefix(completions) 
             line = line[:-len(word)] + prefix
         return line, completions 
  
     
     #--------------------------------------------------------------------------
     # LineFrontEndBase interface 
     #--------------------------------------------------------------------------
 
     def prefilter_input(self, input_string):
         """ Using IPython0 to prefilter the commands to turn them
         in executable statements that are valid Python strings.
         """
         input_string = LineFrontEndBase.prefilter_input(self, input_string)
         filtered_lines = []
         # The IPython0 prefilters sometime produce output. We need to
         # capture it.
         self.capture_output()
         self.last_result = dict(number=self.prompt_number)
         
         ## try:
         ##     for line in input_string.split('\n'):
         ##         filtered_lines.append(
         ##                 self.ipython0.prefilter(line, False).rstrip())
         ## except:
         ##     # XXX: probably not the right thing to do.
         ##     self.ipython0.showsyntaxerror()
         ##     self.after_execute()
         ## finally:
         ##     self.release_output()
 
 
         try:
             try:
                 for line in input_string.split('\n'):
                     filtered_lines.append(
                             self.ipython0.prefilter(line, False).rstrip())
             except:
                 # XXX: probably not the right thing to do.
                 self.ipython0.showsyntaxerror()
                 self.after_execute()
         finally:
             self.release_output()
 
 
 
         # Clean up the trailing whitespace, to avoid indentation errors
         filtered_string = '\n'.join(filtered_lines)
         return filtered_string
 
 
     #--------------------------------------------------------------------------
     # PrefilterFrontEnd interface 
     #--------------------------------------------------------------------------
  
     def system_call(self, command_string):
         """ Allows for frontend to define their own system call, to be
             able capture output and redirect input.
         """
         return os.system(command_string)
 
 
     def do_exit(self):
         """ Exit the shell, cleanup and save the history.
         """
         self.ipython0.atexit_operations()