Fix issue when multiple test processes output data to neotest.

[tlxpro]

I was experimenting with https://github.com/HiPhish/neotest-busted and I had issues with data being corrupted when read after multiple commands to busted completed concurrently. Seems like the issue is with multiple calls to uv_fs_write. According to libuv/libuv#3820 (comment), the responsabilty to control concurrent access to same file must lie with the user.

NVIM v0.11.0-nightly+1fb606b
Build type: Release
LuaJIT 2.1.1713773202
OSX

[rcarriga]

I'm not sure if this actually fixes the issue as you're just sending the write to a new coroutine, you could still have several concurrent writes. Your test is failing for me locally.

I've just pushed a change to prevent concurrent writes, can you check with the latest master if you still the issue?

[tlxpro]

With the new coroutine the async context is no longer managed by libuv as it calls the sync version of fs_write.

local ok, write_err = vim.uv.fs_write(output_fd, data, nil)
assert(ok, write_err)

The test fail on latest master. But doesn't If I use fs_write sync.

[rcarriga]

Ah sorry yes, I've changed it now so it will await the write. I still don't get the test passing with the sync version you have above or with the nio version I've implemented unfortunately

[tlxpro]

It might be due to how my system open files, I have a not so recent version of OSX. 10.15.

It didn't change anything for me when I tried this, but this might work for you.

local open_err, output_fd = nio.uv.fs_open(output_path, "w", tonumber("4010666", 8)) -- with O_SYNC
assert(not open_err, open_err)

[tlxpro]

Just tested again. Is nio.uv.fs_write equivalent to vim.uv.fs_write because the former doesn't work.