Re: Bug/non-determinism in output of maparg() and map commands

2017-05-26 20:43 GMT+03:00 Bram Moolenaar <Bram@moolenaar.net>:
>
> Brett Stahlman wrote:
>
>> >> On Tuesday, May 23, 2017 at 8:25:33 AM UTC-5, Brett Stahlman wrote:
>> >> > On Tue, May 23, 2017 at 4:35 AM, Bram Moolenaar <Bram@moolenaar.net> wrote:
>> >> > >
>> >> > > Brett Stahlman wrote:
>> >> > >
>> >> %--snip--%
>> >> > >
>> >> > > The best solution is probably to also add the raw rhs, with the terminal
>> >> > > codes replaced. This won't work when changing the terminal type, but
>> >> > > that is very unlikely to happen.
>> >> >
>> >> > You mean adding a key such as "raw_rhs" to the dictionary returned by
>> >> > maparg()? If so, then yes this would help, but there would still need to
>> >> > be a way to determine lhs, which is currently even more ambiguous than
>> >> > rhs. While it's true that I probably already have lhs if I'm calling
>> >> > maparg(), I need a way to determine which lhs(s) is/are ambiguous with a
>> >> > given lhs. Mapcheck() gives me only the rhs of the conflicting map. To
>> >> > save and restore, I'd need to know the lhs in canonical form as well.
>> >>
>> >> Perhaps mapcheck() could take an optional arg requesting something more than a simple boolean return. When called with this extra arg, mapcheck() could return a conflicting/ambiguous lhs (or list thereof) in some canonical format (possibly determined by the value of the extra arg itself). As long as the format returned could be fed to maparg(), it would be possible to find conflicting mappings, remove them temporarily, and subsequently restore them...
>> >
>> > If you define a mapping you will want to know whether the mapping
>> > already exists and needs to be restored. For that you can use maparg(),
>> > no need to use mapcheck().
>> >
>> > Not sure why you would want to remove "conflicting" mappings. Perhaps
>> > when you map the ; key, and the user has ;x mapped? Then you would need
>> > a list. Adding a maplist() function would be better than adding
>> > arguments to mapcheck().
>>
>> Yes. Very much like that. I'm implementing a sort of transient mode, in
>> which I'll "shadow" existing maps with very short (generally single
>> character) mappings, which are expected to be ambiguous/conflicting with
>> existing maps, and even builtin operators. Of course, when I exit the
>> transient mode, I'd need to restore the mappings that were shadowed.
>>
>> The global and builtin maps are not a problem, since the transient maps use
>> <buffer> and <nowait>; however, without parsing the output of one of the :map
>> functions, I have no way of knowing which buf-local mappings will be ambiguous
>> with the transient maps I'm defining. And parsing the :map output is
>> problematic for the reasons already mentioned: e.g., no way to tell the
>> difference between function key <F8> and the corresponding 4 characters. I'd
>> actually considered taking some sort of iterative approach: e.g., trying all
>> possible permutations of lhs as input to maparg() and testing the results, in
>> an attempt to deduce the canonical form, but this would be extremely messy,
>> and I don't even know whether it would be deterministic... The maplist()
>> function you mentioned, if it returned all ambiguous left hand sides in
>> canonical form, or even a list of the corresponding maparg()-style
>> dictionaries, would be perfect. Of course, there would also need to be a way
>> to get the rhs's canonical form: e.g., the extra "raw_rhs" key in the maparg()
>> or maplist() dictionary.
>
> OK, so for this you would use maplist() to get the list of mappings to
> disable, use maparg() to get the current mapping, clear the mapping, do
> your stuff, then restore the cleared mappings. You then need to make
> sure you restore the mappings exactly as they were, even when your
> "stuff" fails miserably.
>
> It's a lot easier if we would have a way to temporarily disable
> mappings. It's mostly the same as above, but you won't need to use
> maparg() to get the current mapping and the restore operation. Instead
> you would disable instead of clear, and later re-enable instead of
> restore. Still need to make sure the re-enbling does happen, no change
> in that part.

Not sure I understood what exactly you suggest to disable/restore. All
mappings at once with one command? I would actually disagree here: I
need something similar for translit3, but it only remaps
single-character mappings, leaving most of other user mappings alone.
One mapping at a time? It would be good, but given that request is
temporary remapping naming the functionality enable/disable looks
strange. And there are still issues with determining {lhs}.

One of the logical variants would be `:map <push> {lhs}
{new-rhs}`/`:unmap <push> {lhs}`+`:map <pop> {lhs}`, but this is hard
to implement and is rather limited, though less limited then
enable/disable everything variant.

I would instead suggest a function mappings_dump()/mappings_add():
first is similar to `nvim[_buf]_get_keymap` and should dump all
mappings as a list of maparg()-like dictionaries. Second should define
mappings being given a list of them. Of course, this means that
dictionaries need to be fixed to allow correctly saving/restoring.

The advantages:

1. Easier to implement. Code for creating a maparg() dictionary is
already there, iterating over all mappings is not a problem. Results
needs to be incompatible with maparg() or use additional keys though:
e.g. Neovim altered the contents of `noremap` and `buffer` keys: first
is now 0, 1 or 2 (you can't correctly restore a mapping if you can't
distinguish `map <script>` and `noremap`) and second is a buffer
number or zero.
2. More flexible: you can save and restore everything, push or pop
individual mappings, create a temporary mapping which is just like
mapping X, but has `<Plug>(Translit3TemporaryMap)` lhs instead (to be
returned from `<expr>` mappings in order to select either plugin
behaviour or fall back to previously present user mapping instead).

I can imagine other usages enable/disable or push/pop could not
achieve: generating configuration with mappings like :mkvimrc, but
allows doing adjustments (parsing `:mkvimrc` output is not fun,
especially if you want to be forward compatible), creating a plugin
which analyses how often different mappings are used (need to copy all
mappings to temporary then replace existing mappings with plugin
ones).
3. This is also forward compatible: just need to state in the
documentation that new significant keys may be added in the future to
the dictionaries so they should be preserved.

>
> Big advantage is that if we evern add functionality to mappings, it will
> keep working, while your save/restore pair probably fails.
>
> Ah, your later post goes in the same direction.
>
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>
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