Generalize swiper-all function for different buffer lists

[apella]

Recently a colleague asked me if it was possible to get the same
behaviour as swiper-all with only the buffers of the current
project.

The solution I wrote for him involved a copy of swiper-all-function
as the list of buffers was not variable. I think this is something
that might be useful for others so here's half of that work to allow
others to do the same: search through a custom list of buffers with
all the niceties of swiper-all.

I haven't done the paperwork for the copyright assignment to the FSF
yet so I can't provide swiper-projectile. When I have the paperwork
done I can make a separate PR for that if people are interested.

[basil-conto]

Thanks!

search through a custom list of buffers with all the niceties of swiper-all

I've never really used this functionality, so I'm curious: where does swiper-multi fit in here? How much overlap is there between that and swiper-all? Are there any opportunities for sharing/merging functionality? Could/should swiper-multi be extended instead of swiper-all?

I haven't done the paperwork for the copyright assignment to the FSF yet so I can't provide swiper-projectile. When I have the paperwork done I can make a separate PR for that if people are interested.

I'd personally be more interested in an implementation that uses the built-in and extensible project.el, which is also available from GNU ELPA and GNU-devel ELPA, rather than the third-party projectile. TIA.

[basil-conto]

Nit: Search for STR in all given BUFFERS.

[basil-conto]

Nit: This let* can be a plain let, right?

[apella]

yes, I don't see why not

[apella]

I've never really used this functionality, so I'm curious: where does swiper-multi fit in here? How much overlap is there between that and swiper-all? Are there any opportunities for sharing/merging functionality? Could/should swiper-multi be extended instead of swiper-all?

I haven't really used it either but this question was a good prompt for me to go and learn more about swiper.
swiper-multi doesn't fit this purpose because it means you have to manually select the buffers first. That takes time if you just want to do a quick search in some of the buffers.

swiper-all has some exclusions: With some exceptions, buffers that aren't backed by a file are not searched.
If the two functions were combined and you selected those buffers in swiper-multi then you wouldn't get any results back.

That said, there is some overlap:
swiper-all-action and swiper-multi-action-2 do the same thing but in a slightly different way.
In this case, I think having the different names might actually be helpful. That way, if people change one, they don't break the other.

[basil-conto]

Thanks for looking into this.

swiper-multi doesn't fit this purpose because it means you have to manually select the buffers first.

But in theory it could be extended to take a list of buffers, just like this PR extends swiper-all - hence my question about the two.

If the two functions were combined and you selected those buffers in swiper-multi then you wouldn't get any results back.

Are you saying that swiper-multi fails on non-file-visiting buffers? If so, that sounds like a bug to me.

swiper-all-action and swiper-multi-action-2 do the same thing but in a slightly different way. In this case, I think having the different names might actually be helpful. That way, if people change one, they don't break the other.

Why not merge them into a single function that can be parameterised to behave in one or the other way?