bug: Python error under watched variables when stepping through code

[Shock9616]

Did you check docs and existing issues?

• I have read all the plugin docs
• I have searched the existing issues
• I have searched the existing issues of plugins related to this issue

Neovim version (nvim -v)

v0.11.0

Operating system/version

macOS 15.3.2

Describe the bug

When I start a debugging session, I can select variables to watch as usual and their values are correctly displayed. However, when I begin to step through the code, the variables' values are replaced with the following python error:

Traceback (most recent call last):
    File "/Users/myusername/.local/share/nvim/mason/packages/codelldb/extension/adapter/scripts/codelldb/interface.pv". line 204, in evaluate_as_sbvalue
        value = evaluate_in_context(pycode, exec_context, eval_context)
                ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

There's definitely more to the error but I can't see it as you can see in this picture (I maxxed my display's resolution to get this much) and I can't figure out any way to see the rest of it

If there's a way to get the full error I'll happily get it for you.

Steps To Reproduce

1. Use the following minimal config

-- repro.lua
local root = vim.fn.fnamemodify("./.repro", ":p")

for _, name in ipairs({ "config", "data", "state", "cache" }) do
	vim.env[("XDG_%s_HOME"):format(name:upper())] = root .. "/" .. name
end

local lazypath = root .. "/plugins/lazy.nvim"
if not vim.loop.fs_stat(lazypath) then
	vim.fn.system({ "git", "clone", "--filter=blob:none", "https://github.com/folke/lazy.nvim.git", lazypath })
end
vim.opt.runtimepath:prepend(lazypath)

local plugins = {
	"folke/LazyVim",
	{
		"mfussenegger/nvim-dap",
		dependencies = {
			{
				"igorlfs/nvim-dap-view",
				opts = {},
			},
		},
		config = function()
			local dap = require("dap")

			dap.adapters.codelldb = {
				type = "executable",
				command = "codelldb",
			}

			dap.configurations.c = {
				{
					name = "Launch file",
					type = "codelldb",
					request = "launch",
					program = function()
						return vim.fn.input("Path to executable: ", vim.fn.getcwd() .. "/", "file")
					end,
					cwd = "${workspaceFolder}",
					stopOnEntry = false,
				},
			}
		end,
	},
	{
		"williamboman/mason.nvim",
		opts = {},
	},
}
require("lazy").setup(plugins, {
	root = root .. "/plugins",
})

2. Open Mason and install codelldb
3. Open a C program and compile with debug info
4. Set a breakpoint and start the debugger
5. Watch a variable
6. Step through the program
7. See the error in watch window

Here's a video example:

error.mp4

Expected Behavior

The variable's value should continue to be displayed/updated with no error.

[igorlfs]

Hello! Thanks for reporting! I can reproduce.

There's definitely more to the error but I can't see it as you can see in this picture

Indeed. Unfortunately, virtual lines are a bit awkward when it comes to that. There's a new option to make it less awkward, and enabling it on my end, I can see the full error and it boils to

can't evaluate expressions when the process is running

I'm not sure why this is happening, though. In the meantime, as a workaround, you can add

"expressions": "native"

To your DAP configuration.

Or using Lua:

expressions = "native"

You can read more about this setting here.

[Shock9616]

Ok sounds good! Glad it's reproducable at least 😅

Thanks for the workaround!

[igorlfs]

Can you report this issue upstream? It looks it's caused by a race condition on the adapter side. And even if that's not the case, I'm sure the codelldb maintainers will have some insight. Though, if that goes sideways, the plan is to introduce a small delay before evaluating the expressions.

[Shock9616]

Sure I can do that! Just to make sure, you want me to report to vadimcn/codelldb?

[igorlfs]

Yep!

[Shock9616]

Hey so vadimcn replied and asked for the verbose log, I can't seem to find a way to add that to my config. Am I going to have to create a vscode launch.json file to get that to work or something?

[igorlfs]

Hey so vadimcn replied and asked for the verbose log, I can't seem to find a way to add that to my config.

That requires a VSCode-specific setting, I'm afraid. A workspace configuration (to be more accurate), which is a VSCode thing.

Am I going to have to create a vscode launch.json file to get that to work or something?

launch.json hosts debugging configurations instead of workspace configurations. These debugging configurations can be used with any client, including nvim-dap. Generally speaking, I recommend using it over having predefined configurations in your neovim config. But that's beside the point.

What you can do instead is enabling nvim-dap's verbose logging via :lua require('dap').set_log_level('TRACE'). This will log as much information as nvim-dap gets, but it may not be enough, if that verboseLogging, VSCode-specific setting, enhances logs somehow. But that should get you started.

[igorlfs]

Hello!

Can you try #49? It should fix this issue from nvim-dap-view's side (and without any dirty workarounds).

I've noticed that either the exact same (or a very similar) issue also affects the JS debug adapter, and with the aforementioned PR, it's alright.

[igorlfs]

Closed by #49. If you still manage to reproduce, ping me so I'll reopen this issue.