feat(api) Allow adding expresion to watch

[przepompownia]

Similarly to dapui.eval it'd be good to can add (especially from visual selection) expression to watches. It seems that currently Watches:add_watch is called only for manually typed expressions.

[przepompownia]

I did not found the solution in the previous API but in the new API the example

local function watchExpression(expression)
  dapui.elements.watches.add(expression)
end

vim.api.nvim_create_user_command('DapiUIAddToWatch', function (opts)
  watchExpression(opts.args)
end , {nargs = 1})

shows that it's possible 🎉

[przepompownia]

In my local env have added both cmd and visualmode:
https://github.com/przepompownia/nvim-arctgx/blob/f2350ce06ccd9fbaf6d5b0891429d9c63be308e5/bundleConfig/nvim-dap-ui.lua#L40-L51

I suspect that exposing such feature in the way similar to dapui.eval would make many users happy.

[rcarriga]

Ha didn't even get to post the update before you spotted it, great to hear it being used already 😄

I suspect that exposing such feature in the way similar to dapui.eval would make many users happy.

Great idea, I've added the same ability in the latest commit!

[przepompownia]

Thanks. I looked into the change to ensure if it allows selection in both directions 👍

It would be good to add some docs about the new feature too.