Debug Adapter Protocol implementation

[hariamoor-zz]

Termdebug only works for gdb, which is a major disappointment for the users who've wanted an integrated debugger for years, but don't compile in gcc (or perhaps not at all).

Vimspector implements the Debug Adapter Protocol (DAP) for Vim, which is a common interface to interop with a lot of different debuggers. The author is working to integrate it with Neovim, but is running into some issues concerning our API; see the discussion and his current progress.

Given that we've already merged a debugger plugin from Vim and that we already like to work with protocols like LSP (DAP is the LSP of debuggers, you could say), would you consider an upgrade of termdebug to implement DAP and interface with a multitude of debuggers?

[bfredl]

This would be a welcome contribution. But there is no requirement that it be based on termdebug, likely it is better to develop a DAP client in Lua from scratch (and borrow pieces from termdebug if they be useful).

[hariamoor-zz]

But there is no requirement that it be based on termdebug

Then, for sake of cohesiveness, we should plan to deprecate our support for termdebug. That way, there isn't one Vim-compatible interface for gdb and one non-Vim-compatible interface for everything else.

Edit: This is, of course, when the planned DAP implementation is stable.

[hariamoor-zz]

@bfredl I'm ready to get a PR going if you don't have any other questions or objections. My plan is to write and test the core functionality in Lua, but bind it to the Neovim interface with VimL. I'd also appreciate your continued support in code review on this!

Edit: Forgot to mention that I was planning to start with a fork of Vimspector, as given above, and then port the Python parts to Lua. Then, we could rethink the interface if necessary (I don't think it should be), and start writing configurations for different debuggers.

[justinmk]

Then, for sake of cohesiveness, we should plan to deprecate our support for termdebug

Maybe. No rush, but if we end up with something like vim.lsp then we can kiss TermDebug goodbye.

Forgot to mention that I was planning to start with a fork of Vimspector, as given above, and then port the Python parts to Lua

That might be a useful experiment, but it might be "too much". I would start small (TermDebug might be a better starting point). See what core pieces are missing. E.g. I can imagine that a popup abstraction will be helpful.

NB: don't create dozens of new files scattered everywhere. Keep everything in one file, runtime/lua/vim/dap.lua .