Feat: Conditon for extensions

[HiPhish]

Requested feature

Currently Lualine only looks at the file type in order to determine whether to use an extension. I would like more control by being able to specify a condition boolean thunk as well:

local my_extension = {
    sections = {
        lualine_a = {'filename'}
    },
    filetypes = {'help'}
    condition = function()
        return vim.bo.buftype == 'help'
    end
}

Motivation

Some buffers can be opened like any normal file for editing, or they can be opened for reading only. Help files are the prime example: when writing a help file I want all the usual status line components, but when I open the file by using the :help command I would like to load the extension instead.

I already have in my Vim configuration in after/ftplugin/help.vim the following to hide line numbers and format characters when reading documentation (where they are only distracting) but to keep them when writing documentation:

if &buftype == 'help'
    setlocal foldcolumn=0 nonumber
    finish
endif

setlocal conceallevel=0

I also have similar settings for info and markdown buffers as well by checking for buftype nofile instead.

[hoob3rt]

can't this already be achieved with

local my_extension = {
  sections = {
    lualine_a = {
      {'filename', condition = function() return vim.bo.buftype == 'help' end}
    }
  },
  filetypes = {'help'}
}

Granted this can get pretty rough if you want to create a sophisticated extension.

I like it so I will try creating a pr with it sooner than later. This change should also affect disabled_filetypes. We can change it to condition as well for more control

[HiPhish]

I don't think your example would be sufficient, but I could be wrong. Let's say my default status line contains the mode, file name and position. Let's say I want help files to show the position and file name.

default = {
    sections = {
        lualine_a = {'mode'}
        lualine_b = {'filename'}
        lualine_z = {'position'}
    }
}

extension = {
    sections = {
        lualine_a = {'position'}
        lualine_z = {'filename'}
    }
}

If the condition does not match I want to fall back on the default. Your example looks like it only turns off individual components, but not the entire extension itself. I would have to repeat the default configuration inside the extension configuration:

extension = {
    sections = {
        lualine_a = {
            {'position', condition = is_readonly},
            {'mode', condition = function() return not is_readonly() end}
        },
        lualine_b = {
            {'filename', condition = function() return not is_readonly() end}
        },
        lualine_z = {
            {'filename', condition = is_readonly},
            {'position', condition = function() return not is_readonly() end}
        }
    }
}

Please correct me if I am wrong.

[stale[bot]]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions.

[artem-nefedov]

I would be interested in this as well. Specifically, my usecase is I want to make an extension that works in terminal buffers only, but terminal buffers don't have a filetype.