bug#69305: outline-minor-mode for tabulated-list-mode

[Juri Linkov]

>> >> But tabulated-list-groups is not a defcustom.
>> >> There are no defcustoms here.
>> >
>> > Buffer-menu-group-by _is_ a defcustom, and it is documented thusly:
>> >
>> >   +  "If non-nil, buffers are grouped by function.
>> >   +This function takes one argument: a list of entries in the same format
>> >   +as in `tabulated-list-entries', and should return a list in the format
>> >   +suitable for `tabulated-list-groups'.
>> >
>> > So you are inviting users to write functions that return values of a
>> > certain format, but the format's documentation IMO doesn't make it
>> > clear how to specify a grouping, and for its important part alludes to
>> > another variable (tabulated-list-entries), whose documentation is
>> > suitable for different kind of uses, not for grouping of entries.
>> 
>> The format 'tabulated-list-entries' is input.
>> The format 'tabulated-list-groups' is output.
>
> Yes, I'm well aware of that.
>
>> > Since tabulated-list-groups is such an important part of the
>> > documentation of Buffer-menu-group-by, the doc string of
>> > tabulated-list-groups is in effect part of the doc string of
>> > Buffer-menu-group-by, and should IMO be worded as appropriate for user
>> > options.
>> 
>> The docstring of 'tabulated-list-groups' already
>> sufficiently documents the format:
>
> No, it doesn't document it sufficiently.  As I already said several
> times.
>
>>   (defvar-local tabulated-list-groups nil
>>     "Groups displayed in the current Tabulated List buffer.
>>   This should be either a function, or a list.
>>   If a list, each element has the form (GROUP-NAME ENTRIES),
>>   where:
>> 
>>    - GROUP-NAME is a group name as a string, which is displayed
>>      at the top line of each group.
>> 
>>    - ENTRIES is a list described in `tabulated-list-entries'.
>> 
>> There is no need to duplicate the description of linked
>> 'tabulated-list-entries'.
>
> This is not about duplication.  This is about adding information that
> currently isn't there.
>
>> And here it's clear that the function should add GROUP-NAME to
>> groups from 'tabulated-list-entries'.
>
> Which doesn't clarify the issue at hand even a single bit.

Sorry, I don't understand what is missing here.
Please show an example of changes that you want.