Workaround for empty setBreakpoints response

[mfussenegger]

Looks like delve can send a response that is nil:

.config/nvim/pack/plugins/start/nvim-dap/lua/dap.lua:760: attempt to index local 'resp' (a nil value)

This is with the following adapter config:

  dap.adapters.go = {
    type = 'server',
    host = '127.0.0.1',
    port = 46545
  }

recording.mp4

[theHamsta]

Yeah, I changed this also sometimes but was not sure whether I was doing something wrong. Probably good to check from this case.

[mfussenegger]

I'm actually not sure what is really going on.

From the log it looks like the response is sent twice:

[ DEBUG ] 2021-03-03T22:47:38Z+0100 ] ...rdi/.config/nvim/pack/plugins/start/nvim-dap/lua/dap.lua:837 ]	{
  body = {
    breakpoints = { {
        line = 7,
        source = {},
        verified = true
      } }
  },
  command = "setBreakpoints",
  request_seq = 1,
  seq = 0,
  success = true,
  type = "response"
}
[ WARN ] 2021-03-03T22:47:38Z+0100 ] ...rdi/.config/nvim/pack/plugins/start/nvim-dap/lua/dap.lua:842 ]	"No callback for "	{
  body = {
    breakpoints = { {
        line = 7,
        source = {},
        verified = true
      } }
  },
  command = "setBreakpoints",
  request_seq = 1,
  seq = 0,
  success = true,
  type = "response"
}

The first clears the callback, so the second time there is the No callback for warning.
What I don't get is that although there is a body in the log, it somewhere goes missing.

An assertion like this:

nvim-dap/lua/dap.lua

Lines 847 to 848 in 7dc11c3

	if decoded.success then
	assert(decoded.body, 'There must be a body in a successful response')

Triggers an error.

[mfussenegger]

Looks like the root cause of the issue is that seq is not being increased in delve, and nvim-dap currently relies on that to set the request_seq numbers.

The setBreakpoints response isn't sent twice, that was just the duplicate logging that confused me. But the launch and setBreakpoints have the same request_seq:

[ DEBUG ] 2021-03-03T23:08:14Z+0100 ] ...rdi/.config/nvim/pack/plugins/start/nvim-dap/lua/dap.lua:837 ]	{
  command = "launch",
  request_seq = 1,
  seq = 0,
  success = true,
  type = "response"
}
[ DEBUG ] 2021-03-03T23:08:14Z+0100 ] ...rdi/.config/nvim/pack/plugins/start/nvim-dap/lua/dap.lua:837 ]	{
  body = {
    breakpoints = { {
        line = 7,
        source = {},
        verified = true
      } }
  },
  command = "setBreakpoints",
  request_seq = 1,
  seq = 0,
  success = true,
  type = "response"
}

Given that this sequence numbering issue can lead to other problems I'm not sure if the PR here should be merged as is.

See go-delve/delve#2245 for a bug report

[mfussenegger]

#117 is the proper fix