Re: [Emacs-diffs] /srv/bzr/emacs/emacs-24 r111281: * progmodes/python.el (python-info-current-defun): Fix failed

Re: [Emacs-diffs] /srv/bzr/emacs/emacs-24 r111281: * progmodes/python.el (python-info-current-defun): Fix failed

[Stefan Monnier]

> -                             (python-nav-end-of-defun)
> +                             (save-match-data
> +                               ;; FIXME: avoid cluttering match-data
> +                               ;; where's not wanted.
> +                               (python-nav-end-of-defun))
>                               (+ (point)
>                                  (if (>= (current-indentation) min-indent)
>                                      (1+ (current-indentation))

I suspect this is not The Right Place for the save-match-data, since we
should not assume that current-indentation won't also mess up the
match-data.


        Stefan

Re: [Emacs-diffs] /srv/bzr/emacs/emacs-24 r111281: * progmodes/python.el (python-info-current-defun): Fix failed

[Fabián Ezequiel Gallina]

On 02/19/2013 06:37 PM, Stefan Monnier wrote:
>> -                             (python-nav-end-of-defun)
>> +                             (save-match-data
>> +                               ;; FIXME: avoid cluttering match-data
>> +                               ;; where's not wanted.
>> +                               (python-nav-end-of-defun))
>>                                (+ (point)
>>                                   (if (>= (current-indentation) min-indent)
>>                                       (1+ (current-indentation))
> I suspect this is not The Right Place for the save-match-data, since we
> should not assume that current-indentation won't also mess up the
> match-data.
>
>
>          Stefan

FWIW this very small change corrected the python-info-current-defun 
behavior and was able to pass the test suite I've been working on. So 
far my local test/automated/python-tests.el is covering indentation, 
movement and python-info-* functions completely. Would it be OK to 
introduce these tests into the emacs-24 branch?

Now, I certainly wasn't expecting current-indentation could change 
match-data (could it?). If so, I feel that functions not expected[0] to 
mess with match-data should at least document it.

In this regard, I have a change in the works that will cause python.el 
to stop messing with match-data so much (use of looking-at-p instead of 
looking-at and such), and document those functions that are intended to. 
If everyone agrees I could get this to the emacs-24 branch.

[0] By "functions not expected[0] to mess with match-data" I mean 
functions that are not receiving a regexp as argument.


Regards,
Fabián

Re: [Emacs-diffs] /srv/bzr/emacs/emacs-24 r111281: * progmodes/python.el (python-info-current-defun): Fix failed

[Stefan Monnier]

>> I suspect this is not The Right Place for the save-match-data, since we
>> should not assume that current-indentation won't also mess up the
>> match-data.
> FWIW this very small change corrected the python-info-current-defun behavior
> and was able to pass the test suite I've been working on.

I don't doubt it works, I'm just pointing out that it would be better to
place the save-match-data elsewhere.  The general rule is: put the
save-match-data between the "match" and the corresponding "get
match-data" rather than around some code that might modify the match-data.

> So far my local test/automated/python-tests.el is covering
> indentation, movement and python-info-* functions completely.  Would it
> be OK to introduce these tests into the emacs-24 branch?

Yes, it's OK to add files to emacs-24/test/...

> Now, I certainly wasn't expecting current-indentation could change
> match-data (could it?).

All functions can do it, except for those where it's blatantly obvious
they can't (e.g. `car', `cdr', `match-beginning').  And yes,
current-indentation probably can in sufficiently weird cases.

> If so, I feel that functions not expected[0] to mess
> with match-data should at least document it.

We should indeed document the small set of functions which are
guaranteed not to mess the match-data.

> In this regard, I have a change in the works that will cause python.el to
> stop messing with match-data so much (use of looking-at-p instead of
> looking-at and such), and document those functions that are intended to.
> If everyone agrees I could get this to the emacs-24 branch.

I generally recommend not to go down that route.  Instead, just make sure
all the match-{beginning/end/string} calls come right after the
corresponding search, and if not, place a save-match-data around the
intermediate code.


        Stefan

Re: [Emacs-diffs] /srv/bzr/emacs/emacs-24 r111281: * progmodes/python.el (python-info-current-defun): Fix failed

[Fabián Ezequiel Gallina]

On 02/20/2013 11:01 AM, Stefan Monnier wrote:
>> FWIW this very small change corrected the python-info-current-defun behavior
>> and was able to pass the test suite I've been working on.
> I don't doubt it works, I'm just pointing out that it would be better to
> place the save-match-data elsewhere.  The general rule is: put the
> save-match-data between the "match" and the corresponding "get
> match-data" rather than around some code that might modify the match-data.
Thanks for the clarification, I pushed a change for this in revno 111284.
>> So far my local test/automated/python-tests.el is covering
>> indentation, movement and python-info-* functions completely.  Would it
>> be OK to introduce these tests into the emacs-24 branch?
> Yes, it's OK to add files to emacs-24/test/...
Pushed in revno 111283.
>> In this regard, I have a change in the works that will cause python.el to
>> stop messing with match-data so much (use of looking-at-p instead of
>> looking-at and such), and document those functions that are intended to.
>> If everyone agrees I could get this to the emacs-24 branch.
> I generally recommend not to go down that route.  Instead, just make sure
> all the match-{beginning/end/string} calls come right after the
> corresponding search, and if not, place a save-match-data around the
> intermediate code.

That's good, I will not get picky about match-data modification. In any 
case these replacements of looking-at and string-match are part of a set 
of good and fairly cheap refactors (partially based on 
https://github.com/fgallina/python.el/pull/121).



Thanks,
Fabián