bug#63959: python-mode does not keep indentation in square brackets []

["Andreas Röhler" <andreas.roehler@easy-emacs.de>]

Am 18.06.23 um 17:20 schrieb Konstantin Kharlamov:
> On Sun, 2023-06-18 at 23:56 +0900, kobarity wrote:
>> I wrote:
>>> Eli Zaretskii wrote:
>>>>> From: Konstantin Kharlamov <hi-angel@yandex.ru>
>>>>> Date: Thu, 08 Jun 2023 12:39:23 +0300
>>>>>
>>>>> Usually in programming modes, when previous indentation is kind of
>>>>> "special",
>>>>> the new lines should keep the indentation from the previous line.
>>>>> However, it
>>>>> doesn't work in this case.
>>>>>
>>>>>
>>>>> # Steps to reproduce
>>>>>
>>>>> 1. Create file `test.py` with following content:
>>>>>
>>>>>      for infix in [ # some description
>>>>>                    "_cdata", "_cmeta", "_corig", "_cpool", "_cvol",
>>>>> "_wcorig",
>>>>>                    "indentation is broken here", "bar"]:
>>>>>          print(infix)
>>>>>
>>>>> 2. Open it as `emacs -Q test.py`
>>>>> 3. Put a caret on the 3rd line (which says "indentation is broken"
>>>>> 4. Press TAB
>>>>>
>>>>>
>>>>> ## Expected
>>>>>
>>>>> Indentation won't change
>>>>>
>>>>> ## Actual
>>>>>
>>>>> The line goes back by 4 spaces or so
>>>>>
>>>>> # Additional information
>>>>>
>>>>> emacs version: compiled from latest git a week ago, commit 5cace109d2b
>>>> kobarity, any comments?
>>> I think the current Python mode tries to indent based on parens,
>>> regardless of the indentation of the previous line.  However, it would
>>> also be reasonable to maintain the indentation of the previous line.
>>> I will see if I can implement it.
>> Attached is a patch to implement it.  I introduced a new indent
>> context `:inside-paren-continuation-line' for the continuation lines
>> within paren.  The indent context respects the indentation of the
>> previous line.
>>
>> However, it may happen that the previous line is indented for the
>> inner paren as in the ERT `python-indent-inside-paren-2':
>>
>> data = {'key': {
>>      'objlist': [
>>          {'pk': 1,
>>           'name': 'first'},
>>          {'pk': 2,
>>           'name': 'second'}
>>      ]
>> }}
>>
>> The line "{'pk': 2," is considered as the continuation line, but it
>> should not respect the indentation of the PREVIOUS line "'name':
>> 'first'},".  So skipping such lines with inner parens were needed.
>> It searches backward for the line which starts with the item of the
>> same opening paren as the target line.
>>
>> In the case of the above example, if the target line is "{'pk': 2,",
>> its opening paren is "[" in the line "'objlist': [".  It first checks
>> the previous line "'name': 'first'},", but its opening paren is "{" in
>> "{'pk': 1,".  So this line is skipped.  Next, it checks the line
>> "{'pk': 1," and its opening paren is "[" in the line "'objlist': [",
>> which is same as the target line.  So the target line's indentation
>> will be as same as the line "{'pk': 1,".
>>
>> It would be helpful if you could try this patch.
> Thank you, tested, works for me!
>
>> Does anyone think we should have a customize variable that switches
>> between the traditional behavior of ignoring the indentation of the
>> previous line and this new behavior?
> I doubt it's useful. It is in general how indentation works in many modes, and I
> don't think there ever been a variable to disable that. Stefan Monnier in
> particular has a paper called "SMIE: weakness is power", where such indentation
> is shortly discussed.
>
>
> IMO the question of previous lines indentation isn't raised here, as a more specific rule applies: inside a non-empty list
> indent with its first element. Whereas if list starts empty, as with "[" here, next indents as that line plus offset.