vim.ui.input reports nil for empty string

[Shatur]

Describe the bug

The following code

vim.ui.input({ prompt = 'Data: ' }, function(data) vim.notify(vim.inspect(data)) end)

prints nil for both cancelled dialog and empty input. I would expect to have an empty string on empty input.

System information

• OS: linux
• Neovim version: 0.7
• Dressing config: defaults

To Reproduce Steps to reproduce the behavior:

1. :vim.ui.input({ prompt = 'Data: ' }, function(data) vim.notify(vim.inspect(data)) end)
2. Press <CR>

[stevearc]

This is intentional behavior. The built-in vim.ui.input explicitly treats an empty return string as nil, so we have to do the same to preserve compatibility. https://github.com/neovim/neovim/blob/0adc66171a355a12494d87ebb767d509540c7ef9/runtime/lua/vim/ui.lua#L92-L96

[Shatur]

Oh, I see... But how can I know if a user canceled the dialog or set an empty string?

[stevearc]

Unfortunately, you cannot. I believe this is a limitation of the input() function, which seems to return an empty string when canceled. Since it can't distinguish between empty input and cancel, vim.ui.input can't either.