":read :cmd" reads :cmd output into a buffer

[sidesteps]

trafficstars

Problem

Vims' internal pager 'more' sucks: can't search when neovim opens output in it.

Expected behavior

ability to search when paging with neovims internal pager 'more'

[clason]

Duplicate/part of https://github.com/neovim/neovim/issues/22478 See also https://github.com/neovim/neovim/issues/27811

[clason]

And

For example open any help topic with :help and try searching with '/', you can't, can you?

Of course you can; :help opens a full buffer.

[justinmk]

See also https://github.com/neovim/neovim/issues/5054

Proposal

A short-term, high-leverage, low-cost improvement would be to add :read :<cmd> which opens any :<cmd> output into a buffer. Bram also was favorable to that idea.

Would be nice to see a PR for that... Let's use this issue to track that idea.

Implementation notes

• One way to implement this is to re-use the internals of :help execute() : https://github.com/neovim/neovim/blob/e049c6e4c08a141c94218672e770f86f91c27a11/src/nvim/eval/funcs.c#L1592-L1594
  • Or rather than directly using those internals, the C code can invoke vimscript:

    execute(printf("put=execute('%s')", substitute(escape(<q-args>, '"')
    

• Note also that "mods" should be supported, i.e. :split read :foo should collect the output of :foo before` splitting the window (otherwise this isn't useful).
• A good place for tests would be test/functional/ex_cmds/ . There is currently no read_spec.lua in there, but perhaps could use test/functional/ex_cmds/write_spec.lua as a starting point.

[clason]

For the sake of completeness, we already have :read at home: :put=execute('cmd') (just missing opening a new buffer). Of course, that is hard enough to know about (and even remember) for a shortcut to be valuable. In fact, we have previously discussed adding even more sugar in the form of, say :^ (which is still free real estate, iirc) in analogy to :=.

Open question: do we want to restrict this to Lua command (which, let's be honest, is the primary use case these days)? Or keep :read for vimscript and add :^ as Lua sugar?

[justinmk]

The door is open for those questions, but adding :read :cmd in "vimscript" should be rather low-risk, and makes sense as a first step before the other stuff.

do we want to restrict this to Lua command

why? Ex commands for interactive command line shouldn't require (explicit use of) Lua.

[clason]

why? Ex commands for interactive command line shouldn't require (explicit use of) Lua.

Because that allows us to make the sugar sweeter, as we did for := (which is arguably the most frequent -- but of course not the only -- way to see the pager these days). The point of my comment is to make sure whatever is added also applies to :=.

[justinmk]

The point of my comment is to make sure whatever is added also applies to :=.

I would expect :read :=... to be supported since any :read :<cmd> should simply capture the output of whatever follows :read :.

[lewis6991]

https://github.com/AndrewRadev/bufferize.vim does this which is just a light wrapper around :redir.

We could upstream a form of this without introducing another ex command in C.

[justinmk]

We could upstream a form of this without introducing another ex command in C.

That's the idea. And this doesn't introduce any new Ex command, it only enhances :read in the same way that it already works for :read !....

:read is a basic feature and it absolutely doesn't make sense to introduce a new command or interface for this. :read is the interface for this kind of thing.

The impl of :read doesn't need to be in C, but that's just a detail anyway. The interface is what matters.

[sidesteps]

Reading output of cmd-line command into a buffer is useful.

It does not solve the original issue, (which is now renamed to something completely different:))

The use case is to quickly lookup info in large, read-only info pages. Reading the output of a command into a buffer so that you can do search is not it.

Example is :highlight command. It outputs hundreds of lines that need to be searchable to be useful.

[sidesteps]

If paged output of the command would open in a split window (as :help does) that would be a solution I guess.

[clason]

... which is exactly what is being proposed here.

[justinmk]

Also, I mentioned that https://github.com/neovim/neovim/issues/5054 tracks more elaborate "builtin pager" changes. That is why I renamed this issue to track the more near-term solution of enhancing :read.

[bwalshe]

I had a go at this, but I am not sure I have the right approach. Could I get some feedback before going any further please?

https://github.com/bwalshe/neovim/blob/read_cmd_to_buffer/src/nvim/ex_docmd.c#L5643

[tris203]

I had a go at this, but I am not sure I have the right approach. Could I get some feedback before going any further please?

https://github.com/bwalshe/neovim/blob/read_cmd_to_buffer/src/nvim/ex_docmd.c#L5643

Your best option will be to open a draft PR. People will give feedback there