inlay_hint: "Failed to delete autocmd" error when closing a buffer

[MariaSolOs]

Problem

With the latest nightly release, I'm seeing the following error every time I close a buffer:

So far I've seen this happen with Lua and Rust files.

Note that this doesn't happen with NVIM v0.10.0-dev-692+g86ce3878d.

Steps to reproduce

The only inlay-hint related setup I have is this pair of autocommands that toggles inlay hints:

    if buf_client.supports_method 'textDocument/inlayHint' then
        local inlay_hints_group = vim.api.nvim_create_augroup('ToggleInlayHints', { clear = false })

        -- Initial inlay hint display.
        local mode = vim.api.nvim_get_mode().mode
        vim.lsp.inlay_hint(bufnr, mode == 'n' or mode == 'v')

        vim.api.nvim_create_autocmd('InsertEnter', {
            group = inlay_hints_group,
            buffer = bufnr,
            callback = function()
                vim.lsp.inlay_hint(bufnr, false)
            end,
        })
        vim.api.nvim_create_autocmd('InsertLeave', {
            group = inlay_hints_group,
            buffer = bufnr,
            callback = function()
                vim.lsp.inlay_hint(bufnr, true)
            end,
        })
    end

The rest of my LSP configuration is here.

Expected behavior

For there to be no error.

Neovim version (nvim -v)

NVIM v0.10.0-dev-709+gce56ad2ba

Vim (not Nvim) behaves the same?

No

Operating system/version

Mac Ventura 13.4.1

Terminal name/version

kitty 0.28.1

$TERM environment variable

xterm-kitty

Installation

bob

[MariaSolOs]

This seems to have been caused by #24411. Moreover, I'm not the only one seeing this error, see DNLHC/glance.nvim#57

[MariaSolOs]

As extra information: I discovered that this always happens when using bwipeout, but not with bdelete (at least I haven't seen it happen yet). This kind of explains the error since the former removes the buffer-local autocommands.

[justinmk]

@catlee

[catlee]

I'm having some problems reproducing this. It doesn't happen all the time, I wonder if there's something racing between bwipeout deleting buffer-local autocommands and the disable() function trying to delete the autocommands as well.

When trying to debug this, I discovered that we are calling nvim_buf_attach each time the inlay hints are enabled. This results in many callbacks being registered on the buffer, and so disable is called multiple times when closing the buffer.

This is a result of my previous PR which removed the enabled field from the internal inlay_hint state table.

I think we need to re-introduce that field, since there doesn't seem to be another way to track when we've registered buffer event handlers, nor is there a way to un-register them?

[justinmk]

since there doesn't seem to be another way to track when we've registered buffer event handlers, nor is there a way to un-register them?

To unregister a particular handler one would need to remember the id returned by nvim_create_autocmd()

[MariaSolOs]

@catlee thank you for looking into it! If it helps, I could always reproduce it with this command here.

[catlee]

since there doesn't seem to be another way to track when we've registered buffer event handlers, nor is there a way to un-register them?

To unregister a particular handler one would need to remember the id returned by nvim_create_autocmd()

I'm referring to the buffer callbacks here: https://github.com/neovim/neovim/blob/master/runtime/lua/vim/lsp/inlay_hint.lua#L153.

After setting up on_detach / on_reload callbacks, there doesn't seem to be a way to un-register them.

[catlee]

@catlee thank you for looking into it! If it helps, I could always reproduce it with this command here.

Thanks. It only reproduces for me when I have multiple buffers open.

[justinmk]

:help nvim_buf_detach() mentions :help api-lua-detach:

In-process Lua callbacks can detach by returning `true`. This will detach all
callbacks attached with the same |nvim_buf_attach()| call.

I almost missed that 😅

[catlee]

:help nvim_buf_detach() mentions :help api-lua-detach:

In-process Lua callbacks can detach by returning `true`. This will detach all
callbacks attached with the same |nvim_buf_attach()| call.

I almost missed that 😅

Thanks, that's good to know. I'm not sure how I can use that in this case.

The current code ends up calling nvim_buf_attach every time inlay hints are enabled. If the user toggles hints on/off multiple times without triggering the on_detach or on_reload buffer events, then we end up registering the callbacks multiple times.