Crash upon tab-completion when there's a non-subscriptable key in globals()

[gerritholl]

When I commit a serious crime, I can crash ipython. The crime is: globals()[0]=0. The problem is illustrated below:

$ ipython3
WARNING: IPython History requires SQLite, your history will not be saved
Python 3.3.3 (default, Dec 12 2013, 11:13:02) 
Type "copyright", "credits" or "license" for more information.

IPython 1.1.0 -- An enhanced Interactive Python.
?         -> Introduction and overview of IPython's features.
%quickref -> Quick reference.
help      -> Python's own help system.
object?   -> Details about 'object', use 'object??' for extra details.

In [1]: %config Application.verbose_crash=True

In [2]: globals()[0]=0

In [3]: a<Tab>

Then follows the attached traceback, ultimately leading to TypeError: 'int' object is not subscriptable.

[gerritholl]

TypeErrorPython 3.3.3: /nobackup/smhid10/sm_gerho/venv/python-3.3/bin/python3.3
                                                   Fri Jan 24 14:40:46 2014
A problem occured executing Python code.  Here is the sequence of function
calls leading up to the error, with the most recent (innermost) call last.
/nobackup/smhid10/sm_gerho/venv/python-3.3/lib/python3.3/site-packages/IPython/core/completer.py in complete(self=<IPython.core.completer.IPCompleter object>, text='a', line_buffer='a', cursor_pos=1)
    886 
    887         # Start with a clean slate of completions
    888         self.matches[:] = []
    889         custom_res = self.dispatch_custom_completer(text)
    890         if custom_res is not None:
    891             # did custom completers produce something?
    892             self.matches = custom_res
    893         else:
    894             # Extend the list of completions with the results of each
    895             # matcher, so we return results to the user from all
    896             # namespaces.
    897             if self.merge_completions:
    898                 self.matches = []
    899                 for matcher in self.matchers:
    900                     try:
--> 901                         self.matches.extend(matcher(text))
        self.matches.extend = <built-in method extend of list object at 0x7f5a79fbc050>
        matcher = <bound method IPCompleter.python_matches of <IPython.core.completer.IPCompleter object at 0x7f5a7a21cf10>>
        text = 'a'
    902                     except:
    903                         # Show the ugly traceback if the matcher causes an
    904                         # exception, but do NOT crash the kernel!
    905                         sys.excepthook(*sys.exc_info())
    906             else:
    907                 for matcher in self.matchers:
    908                     self.matches = matcher(text)
    909                     if self.matches:
    910                         break
    911         # FIXME: we should extend our api to return a dict with completions for
    912         # different types of objects.  The rlcomplete() method could then
    913         # simply collapse the dict into a list for readline, but we'd have
    914         # richer completion semantics in other evironments.
    915         self.matches = sorted(set(self.matches))
    916         #io.rprint('COMP TEXT, MATCHES: %r, %r' % (text, self.matches)) # dbg

/nobackup/smhid10/sm_gerho/venv/python-3.3/lib/python3.3/site-packages/IPython/core/completer.py in python_matches(self=<IPython.core.completer.IPCompleter object>, text='a')
    653                 matches = self.attr_matches(text)
    654                 if text.endswith('.') and self.omit__names:
    655                     if self.omit__names == 1:
    656                         # true if txt is _not_ a __ name, false otherwise:
    657                         no__name = (lambda txt:
    658                                     re.match(r'.*\.__.*?__',txt) is None)
    659                     else:
    660                         # true if txt is _not_ a _ name, false otherwise:
    661                         no__name = (lambda txt:
    662                                     re.match(r'.*\._.*?',txt) is None)
    663                     matches = list(filter(no__name, matches))
    664             except NameError:
    665                 # catches <undefined attributes>.<tab>
    666                 matches = []
    667         else:
--> 668             matches = self.global_matches(text)
        matches = undefined
        self.global_matches = <bound method IPCompleter.global_matches of <IPython.core.completer.IPCompleter object at 0x7f5a7a21cf10>>
        text = 'a'
    669 
    670         return matches
    671 
    672     def _default_arguments_from_docstring(self, doc):
    673         """Parse the first line of docstring for call signature.
    674 
    675         Docstring should be of the form 'min(iterable[, key=func])\n'.
    676         It can also parse cython docstring of the form
    677         'Minuit.migrad(self, int ncall=10000, resume=True, int nsplit=1)'.
    678         """
    679         if doc is None:
    680             return []
    681 
    682         #care only the firstline
    683         line = doc.lstrip().splitlines()[0]

/nobackup/smhid10/sm_gerho/venv/python-3.3/lib/python3.3/site-packages/IPython/core/completer.py in global_matches(self=<IPython.core.completer.IPCompleter object>, text='a')
    306         """Compute matches when text is a simple name.
    307 
    308         Return a list of all keywords, built-in functions and names currently
    309         defined in self.namespace or self.global_namespace that match.
    310 
    311         """
    312         #print 'Completer->global_matches, txt=%r' % text # dbg
    313         matches = []
    315         n = len(text)
    316         for lst in [keyword.kwlist,
    317                     list(builtins.__dict__.keys()),
    318                     list(self.namespace.keys()),
    319                     list(self.global_namespace.keys())]:
    320             for word in lst:
--> 321                 if word[:n] == text and word != "__builtins__":
        word = 0
        n = 1
        text = 'a'
    322                     match_append(word)
    323         return matches
    324 
    325     def attr_matches(self, text):
    326         """Compute matches when text contains a dot.
    327 
    328         Assuming the text is of the form NAME.NAME....[NAME], and is
    329         evaluatable in self.namespace or self.global_namespace, it will be
    330         evaluated and its attributes (as revealed by dir()) are used as
    331         possible completions.  (For class instances, class members are are
    332         also considered.)
    333 
    334         WARNING: this can still invoke arbitrary C code, if an object
    335         with a __getattr__ hook is evaluated.
    336 

TypeError: 'int' object is not subscriptable

**********************************************************************

Oops, ipython crashed. We do our best to make it stable, but...

A crash report was automatically generated with the following information:
  - A verbatim copy of the crash traceback.
  - A copy of your input history during this session.
  - Data on your current ipython configuration.

It was left in the file named:
        '/home/sm_gerho/.ipython/Crash_report_ipython.txt'
If you can email this file to the developers, the information in it will help
them in understanding and correcting the problem.

You can mail it to: The IPython Development Team at ipython-dev@scipy.org
with the subject 'ipython Crash Report'.

If you want to do it now, the following command will work (under Unix):
mail -s 'ipython Crash Report' ipython-dev@scipy.org < /home/sm_gerho/.ipython/Crash_report_ipython.txt

To ensure accurate tracking of this issue, please file a report about it at:
https://github.com/ipython/ipython/issues

[minrk]

There are all kinds of ways to do horrible things that will crash IPython, or make Python in general unusable. How did you come across this particular case? I doubt it's worth protecting against it.

[gerritholl]

It happened by accident quite deep in a long-lived ipython session, assigning a key in a dictionary not realising it was pointing to globals(). I don't know if it's worth fixing, but I reported it anyhow. To be honest, I would expect the Python interpreter to complain about assigning a key that is not a string in a namespace, but that's to be discussed at another forum.

[takluyver]

It no longer crashes, but you still see a traceback. I think it's valid to say that IPython should be nice about this, so I'm leaving the issue open but giving it the lowest priority.