feat: Add Prettier formatter

nix/neovim-overlay.nix

@@ -130,6 +130,7 @@ with final.pkgs.lib; let
     shfmt
     stylua
     biome
+    nodePackages.prettier
   ];
 in {
   # This is the neovim derivation returned by the overlay.

nvim/lua/lib/init.lua

@@ -2,6 +2,7 @@
 local M = {}
 
 M.lsp = require('lib.lsp')
+M.prettier = require('lib.prettier')
 
 ---Find the root of a project based on `vim.g.root_spec`. Defaults to
 ---`{ '.git' }` if unset.

nvim/lua/lib/prettier.lua

@@ -0,0 +1,54 @@
+---@class lib.prettier
+local M = {}
+
+---@alias ConformCtx {buf: number, filename: string, dirname: string}
+
+M.supported = {
+  'css',
+  'graphql',
+  'handlebars',
+  'html',
+  'javascript',
+  'javascriptreact',
+  'json',
+  'jsonc',
+  'less',
+  'markdown',
+  'markdown.mdx',
+  'scss',
+  'typescript',
+  'typescriptreact',
+  'vue',
+  'yaml',
+}
+
+---Check if a parser exists for the given context.
+---@param ctx ConformCtx
+function M.has_parser(ctx)
+  local ft = vim.bo[ctx.buf].filetype --[[@as string]]
+
+  -- Default filetypes are always supported.
+  if vim.tbl_contains(M.supported, ft) then
+    return true
+  end
+
+  -- Otherwise, check if a parser can be inferred.
+  local inferred = vim.fn.system({ 'prettier', '--file-info', ctx.filename })
+
+  ---@type boolean, string?
+  local ok, parser = pcall(function()
+    return vim.fn.json_decode(inferred).inferredParser
+  end)
+
+  return ok and parser and parser ~= vim.NIL
+end
+
+---Check if a Prettier config file exists in the current context.
+---@param ctx ConformCtx
+function M.has_config(ctx)
+  vim.fn.system({ 'prettier', '--find-config-path', ctx.filename })
+
+  return vim.v.shell_error == 0
+end
+
+return M

nvim/lua/plugins/formatting/conform-nvim.lua

@@ -32,25 +32,40 @@ return {
         return { timeout_ms = 3000, lsp_format = 'fallback' }
       end,
 
+      -- Prettier is last but only activated if there is a config available,
+      -- thereby giving it priority only when it is wanted.
       formatters_by_ft = {
-        css = { 'biome' },
+        css = { 'biome', 'prettier' },
         fish = { 'fish_indent' },
-        graphql = { 'biome' },
-        javascript = { 'biome' },
-        javascriptreact = { 'biome' },
-        json = { 'biome' },
-        jsonc = { 'biome' },
+        graphql = { 'biome', 'prettier' },
+        handlebars = { 'prettier' },
+        html = { 'prettier' },
+        javascript = { 'biome', 'prettier' },
+        javascriptreact = { 'biome', 'prettier' },
+        json = { 'biome', 'prettier' },
+        jsonc = { 'biome', 'prettier' },
         lua = { 'stylua' },
+        less = { 'prettier' },
+        markdown = { 'prettier' },
+        ['markdown.mdx'] = { 'prettier' },
+        scss = { 'prettier' },
         sh = { 'shfmt' },
-        typescript = { 'biome' },
-        typescriptreact = { 'biome' },
-        vue = { 'biome' },
+        typescript = { 'biome', 'prettier' },
+        typescriptreact = { 'biome', 'prettier' },
+        vue = { 'biome', 'prettier' },
+        yaml = { 'prettier' },
       },
 
       formatters = {
         biome = {
           require_cwd = true,
         },
+        prettier = {
+          condition = function(_, ctx)
+            return MarleyVim.prettier.has_parser(ctx)
+              and MarleyVim.prettier.has_config(ctx)
+          end,
+        },
       },
     })