do_inspect lets ipython compute the info twice

[jankatins]

Found this while trying to understand what is needed to make a decorated method get the same signature/completions as the original one, even on py2.7.

From https://github.com/ipython/ipykernel/blob/master/ipykernel/ipkernel.py#L247:

    def do_inspect(self, code, cursor_pos, detail_level=0):
        name = token_at_cursor(code, cursor_pos)
        info = self.shell.object_inspect(name) # computes the complete info
[...]
        if info['found']:
            info_text = self.shell.object_inspect_text(
                name,
                detail_level=detail_level,
            ) # computes it again as a first step
            data['text/plain'] = info_text
[...]

IMO it would be ok to replace the first self.shell.object_inspect(...) with a info = self.shell._object_find(name) and then use if info.found:. The problem is I don't understand what the with self.builtin_trap: in the object_inspect method does (source) and if that's already needed for self.shell._object_find.

[minrk]

That makes good sense to me. I just want to avoid calling private APIs in IPython from ipykernel. I think we need to take a pass on oinspect in IPython to make a few more ways to call its pieces.

[jankatins]

oinspect probably also needs a pass as inspect.getfullargspec is deprecated ( https://docs.python.org/3/library/inspect.html#inspect.getfullargspec and matplotlib/matplotlib#5014 (comment)) and using the new Signature interface will help with things like getting the proper signature from decorated functions (see matplotlib/matplotlib#4829 (comment) and following comments) updated: getting the call signature from the __wrapped__ func seems to work already on python 3.4.