fix: properly handle buffer deletion

[tomtomjhj]

Problems

• If dap-view buffer is :bwipeout-ed, subsequent close() raises invalid buffer error while attempting to nvim_buf_delete (= bwipeout) the buffer because the buffer is not removed from the state.
• quit_buf_autocmd is weird. BufDelete is invoked when a buffer becomes unlisted. So, since dap-view buffer is already unlisted, closing it with commands like :q does not invoke the BufDelete autocmd.

Solution:

• Let close() check the validity of the buffer first.
• Use BufWipeout autocmd.
• Let the BufWipeout callback first remove the buffer from dap-view state to avoid deleting the buffer inside BufWipeout (E937).

[igorlfs]

Not gonna lie, I'm not an expert when it comes to wiping out buffers and such.

quit_buf_autocmd is weird.

Indeed, I yoinked it from nvim-tree, and then made some modifications. Do you think it's possible to get rid of it completely? We could create autocmd with a pattern to match dap-view's buffers.

[tomtomjhj]

Not gonna lie, I'm not an expert when it comes to wiping out buffers and such.

haha terms used in nvim's api is somewhat different from the legacy vim stuff, adding more confusion to the already confusing vim autocmd system.

Do you think it's possible to get rid of it completely? We could create autocmd with a pattern to match dap-view's buffers.

That would also work, as long as it is a BufWipeout. What I thought is weird was that it was using BufDelete, which won't be triggered at all. I believe the fixed implementation I proposed in this PR should also be fine.

[igorlfs]

Thanks for the contribution!

For now, we'll stick with the quit_buf_autocmd. I may refactor that when we finally get multi session support.