Save nvim-dap breakpoints with session

[laoumh]

Hello everyone!

I just wrote a little module to save nvim-dap breakpoints along with the session. The solution is based off of mfussenegger/nvim-dap#198 (comment) and uses auto-session's Command Hooks to trigger saving, loading and deleting the breakpoints file.

Module intended behavior:

• Saves the session breakpoints to a .json file with the same name and in the same dir as the session .vim file (including named sessions)
• Deletes the breakpoints file if there's no breakpoints when the session is saved
• Deletes the breakpoints file if the session is deleted
• When breakpoints are being restored, the module loads the target file to a hidden buffer, if needed. This is because nvim-dap depends that the file is loaded to a buffer to set a breakpoint in it.

What made writing this module seamless were functions like current_session_name(), made available at auto-session.lib, and the command hooks feature, that allow triggering actions at save, restore and delete session events.

Here is the code:

-- Suppose this file is saved as <nvim-config-path>/lua/utils/session-breakpoints.lua

--[[ Helper functions ]]
local function get_breakpoints_path()
  local Lib = require('auto-session.lib')
  local session_dir = require('auto-session').get_root_dir()
  local session_name = Lib.current_session_name()
  local bp_path = session_dir .. Lib.escape_session_name(session_name) .. '.json'
  return bp_path
end


local function open_file(fpath, mode)
  local fp = io.open(fpath, mode)
  assert(fp, "Couldn't open file " .. fpath)
  return fp
end


local function get_buffer_number(fpath)
  local bufnr = vim.fn.bufnr(fpath, true)
  -- Load the file if it wasn't loaded by the session
  if vim.fn.bufloaded(bufnr) == 0 then
    vim.api.nvim_buf_call(bufnr, vim.cmd.edit)
  end
  return bufnr
end


--[[ Module functions ]]
local M = {}

function M.save_session_breakpoints()
  local savepath = get_breakpoints_path()
  local Breakpoints = require('dap.breakpoints')
  local breakpoints_by_buf = Breakpoints.get()

  if vim.tbl_isempty(breakpoints_by_buf)  then
    -- If there's no breakpoints but the breakpoint file exists,
    -- erase the file
    if vim.fn.filereadable(savepath) > 0 then
      vim.fn.delete(savepath)
    end
    return nil
  end

  -- Map breakpoints to corresponding file
  local breakpoints_by_file = {}
  for buf, buf_bps in pairs(breakpoints_by_buf) do
    local fname = vim.api.nvim_buf_get_name(buf)
    breakpoints_by_file[fname] = buf_bps
  end

  -- Save breakpoints
  local fp = open_file(savepath, 'w')
  fp:write(vim.fn.json_encode(breakpoints_by_file))
  fp:close()
  vim.notify("Saved breakpoints: " .. savepath)
end


function M.restore_session_breakpoints()
  local bp_path = get_breakpoints_path()
  -- If no breakpoints file, there's nothing to do
  if vim.fn.filereadable(bp_path) == 0 then
    return nil
  end
  local fp = open_file(bp_path, 'r')
  local content = fp:read('*a')
  local breakpoints_by_file = vim.fn.json_decode(content)
  fp:close()

  local Breakpoints = require('dap.breakpoints')
  for fname, breakpoints in pairs(breakpoints_by_file) do
    local bufnr = get_buffer_number(fname)
    for _, bp in pairs(breakpoints) do
      local line = bp.line
      local opts = {
        condition = bp.condition,
        log_message = bp.logMessage,
        hit_condition = bp.hitCondition
      }
      Breakpoints.set(opts, bufnr, line)
    end
  end
end


function M.delete_session_breakpoints()
  local bp_path = get_breakpoints_path()
  vim.fn.delete(bp_path)
end


return M

Then attach the module functions to the command hooks when setting up auto-sessions:

local session_breakpoints = require('utils.session-breakpoints')

require('auto-session').setup({
  -- ... other configs ...
  post_save_cmds = { 
    ...
    session_breakpoints.save_session_breakpoints,
  },
  post_restore_cmds = { 
    ...
    session_breakpoints.restore_session_breakpoints,
  },
  pre_delete_cmds = { 
    ...
    session_breakpoints.delete_session_breakpoints 
  },
},

Suggestions and corrections are welcomed!

[rmagatti]

That's pretty cool @laoumh. This could be a good addition to the wiki, and we could mention it in a new "advanced hooks usage" section in the README as well

[laoumh]

@rmagatti ok, I'll make a wiki addition. Any naming suggestion for the top page, like "Recipes" or "Command Hooks"?

[rmagatti]

Advanced Hooks Usage would be my suggestion or even just Example Hooks

[laoumh]

Hello @rmagatti!

It seems the workflow for Wikis is a little different, I can't directly open a PR to it. And, right now, it seems the Wiki isn't open for external editing. From the Docs:

By default, only people with write access to your repository can make changes to wikis, although you can allow everyone on GitHub.com to contribute to a wiki in a public repository.

There is a convoluted suggestion to recreate the Wiki in my own fork, make the changes and submit the link, but you would have to merge the changes yourself.

So, would you like to open the Wiki for community editing or for yourself to merge the addition?

[rmagatti]

Hey @laoumh sorry about the wait, I've enabled wiki editing by anyone. Thanks again!

[cameronr]

We now support saving extra data along with a session and have a recipe for saving DAP breakpoints in the readme