do_filter() behaves differently under nvim than vim (less doesn't work)

[aktau]

Interested in how the new do_filter -> os_call_shell -> ... chain was working out for is, I tried a few things in the source directory:

$ vim
:!less CMakeLists.txt
# can scroll around and do other things that less does

$ ./build/bin/nvim
:!less CMakeLists.txt
# less prints the entire file and then exits, being indistinguishable from cat

I tried to run it directly from the commandline (wrongly) and got this assertion:

➜  neovim git:(master) ./build/bin/nvim -s ":less CMakeLists.txt"
Cannot open for reading: ":less CMakeLists.txt"
Assertion failed: (0), function uv_close, file /Users/aktau/github/neovim/neovim/.deps/build/src/libuv/src/unix/core.c, line 160.
[1]    806 abort      ./build/bin/nvim -s ":less CMakeLists.txt"

ping @tarruda, any ideas? (the regular vim used was 7.4.488).

[tarruda]

This was probably introduced in #1365 because os_call_shell no longer lets the child process inherit nvim std file descriptors. less is simply one of the programs that behave differently if stdout is a tty.

Essentially this is the same problem reported in #1044: While it could be easily fixed at the moment, it will stop working once Nvim externalizes its UI, because it no longer will be a terminal program.

[aktau]

This was probably introduced in #1365

I had an inkling. I'm wondering if this sort of feature is being used by a lot of people... since we don't be able to emulate it with nvim as a server.

[aktau]

@tarruda what about emulating a pty and updating a dynamic buffer? That would it could possibly work with remote clients as well.

[tarruda]

I'm wondering if this sort of feature is being used by a lot of people

If there are, then these people won't be losing a lot by migrating to nvim. Here's a way of invoking a terminal program from Nvim that currently that works: <ctrl+z>less CMakeLists.txt<cr>

This feature is as useful as the :shell command which was removed from Nvim some months ago. I won't be surprised if this feature is broken in gVim as the :shell command was.

@tarruda what about emulating a pty and updating a dynamic buffer? That would it could possibly work with remote clients as well.

Yes, terminal emulation is something that fits well into a plugin, and could have a much cleaner implementation(no 'updatetime' hacks) in Nvim, though right now this would probably require python for it's pty libraries.

[aktau]

If there are, then these people won't be losing a lot by migrating to nvim. Here's a way of invoking a terminal program from Nvim that currently that works: <ctrl+z>less CMakeLists.txt

True. Can this be triggered from a script? (the backgrounding, et cetera).

[tarruda]

True. Can this be triggered from a script? (the backgrounding, et cetera).

The backgrounding can be entered with the :suspend command or simply mapping something to <c-z>, typing something on the command-line after backgrounding would more complicated

[justinmk]

Closing this as "wontfix", :term is the workaround.