Prettier: Using Different Args Based On Filetypes

[DennisTheMenace780]

At my work we use Ruby and Typescript (monolith), and we're looking at integrating the prettier/plugin-ruby to format the Ruby code we use. We also use Prettier to format our Typescript code.

Reading the BUILTIN_CONFIG.md it seems we can add custom filetypes, so I should be able to tell Prettier to attach on Ruby files, that seems easy enough. Now, the Ruby plugin gets installed and ran via the following command ./node_modules/.bin/prettier --plugin=@prettier/plugin-ruby --write '**/*'.

But of course the command to run the formatter for Typescript is going to be different, so I need to figure out a way to dynamically tell none-ls to use a specific command on Ruby files, and a different command on Typescript files; That is the main problem I am trying to solve for.

Reading the BUILTIN_CONFIG.md#arguments section, it appears that using a function to specify what the extra arguments should be might be hte way to go here. However, it's not clear to me how I can insert the filetype into that function so that when I have Ruby files a different command runs than the one used for Typescript files. A basic example is provided in the docs for dynamic args:

local sources = {
    null_ls.builtins.formatting.prettier.with({
        extra_args = function(params)
            return params.options
                and params.options.tabSize
                and {
                    "--tab-width",
                    params.options.tabSize,
                }
        end,
    }),
}

So for now, i'll open this up for discussion and I would love to hear what others think. I'll be using this thread to chip away at the problem as I work towards solving it, unless someone has a suggestion right out of the gate.

[DennisTheMenace780]

From MAIN.md#params it seems that the params.options refers to the options supplied by the language server protocol. I wasn't sure what tabSize refers to, however, if we take a look at the LSP specification then it becomes apparent that tabSize is the option for the language protocol, and therefor, we can probably use params.options.languageId as a way to change the prettier command at runtime based on the language we're working with.

Will have to experiment and report back.

[DennisTheMenace780]

Alright, so params.options.languageId wasn't the play, but fortunately the params object has a filetype associated with it, so right now I have my null-ls.lua set up like this:

local log = require("null-ls.logger")

local null_ls_status_ok, null_ls = pcall(require, "null-ls")
if not null_ls_status_ok then
	return
end

local formatting = null_ls.builtins.formatting

null_ls.setup({
	debug = true,
	sources = {
		formatting.prettier.with({
			extra_args = function(params)
				if params then
					log:info(params.filetype)
				end

				return {
					"--config",
					"--arrow-parens",
					"avoid",
				}
			end,
			extra_filetypes = { "rb", "ruby" },
		}),
	},
	diagnostics_format = "[#{c}] #{m} (#{s})",
})

I was able to see in the null-ls.log that my log was showing up with typescriptreact, as well as the commands I passed in above:

[INFO  Tue 12 Mar 18:46:35 2024] /Users/dennisjosephgray/.config/nvim/lua/user/lsp/null-ls.lua:34: typescriptreact
[DEBUG Tue 12 Mar 18:46:35 2024] /Users/dennisjosephgray/.local/share/nvim/site/pack/packer/start/null-ls.nvim/lua/null-ls/helpers/generator_factory.lua:321: spawning command "/Users/dennisjosephgray/jobber/Jobber/node_modules/.bin/prettier" at /Users/dennisjosephgray/jobber/Jobber with args { "--stdin-filepath", "/Users/dennisjosephgray/jobber/Jobber/<sanitized-file-path>.tsx", "--config", "--arrow-parens", "avoid" }

This gives me confidence that i'm on the right track for getting the plugin to execute the Ruby plugin.

[DennisTheMenace780]

Great news! It got figured out. It turns out to be quite simple, but this works for me:

null_ls.setup({
	debug = false,
	sources = {
		formatting.prettier.with({
			extra_args = function(params)
				if params.filetype == "ruby" then
					return { "--plugin=@prettier/plugin-ruby" }
				end

				return {
					"--config",
					"--arrow-parens",
					"avoid",
				}
			end,
			extra_filetypes = { "ruby" },
		}),
	},
	diagnostics_format = "[#{c}] #{m} (#{s})",
})

For others interested, I think this will be a great starting point for you to continue building off of, but the key elements of getting prettier/ruby to work are here.