set a breakpoint automatically on launch?

[jyn514]

Problem Statement

i have a codebase with an assert() macro. i want to break on any line where an assertion fails, across any run of this program, without having to set a breakpoint manually each time i open vim.

Possible Solutions

my first thought was to add some kind of hook to dap.configurations.cpp. but i don't see any hook that looks relevant? dap.listeners.on_config is not what i want because it runs before the process attaches, not after.

Considered Alternatives

manually create the breakpoint each time i open vim. this is tedious and feels like it shouldn't be necessary.

[mfussenegger]

I'm not sure I follow. You can call dap.set_breakpoint at any time before sessions start?

And depending on the debug adapter you can configure the exception breakpoints so that it automatically stops when it encounters an exception.

You can configure these e.g. like:

require('dap').defaults.fallback.exception_breakpoints = {'raised'}

See :help dap.set_exception_breakpoints()

[jyn514]

oh! you're absolutely right, i could hook this when nvim loads the workspace, it doesn't have to be after the session has started. thanks :)

And depending on the debug adapter you can configure the exception breakpoints so that it automatically stops when it encounters an exception.

that doesn't work for this codebase because it doesn't use unwinding/c++ exceptions.

[jyn514]

You can call dap.set_breakpoint at any time before sessions start?

wait hold on, i don't understand - that says "Creates or removes a breakpoint at the current line." i guess that means "at the current cursor"? is there a way to set a breakpoint that's not tied to the cursor?

[mfussenegger]

There will be with #1388

In the meantime you can either temporarly change the cursor (nvim_win_set_cursor) before calling set_breakpoint or you could use the internal API (

nvim-dap/lua/dap/breakpoints.lua

Line 107 in 12b846b

function M.toggle(opts, bufnr, lnum)

) - but keep in mind that this internal API can change/break from one commit to the next with no deprecation warnings.

[jyn514]

my first thought was to add some kind of hook to dap.configurations.cpp. but i don't see any hook that looks relevant? dap.listeners.on_config is not what i want because it runs before the process attaches, not after.

for posterity: i found a way to do this, it's dap.listeners.after['event_initialized']['plugin'] = function() end; documented here: https://microsoft.github.io/debug-adapter-protocol/specification#Events_Initialized and in :h dap-listeners