nvim: Add json formatting, auto gather filetypes

Added json to be formatted by prettier like the other javascript-close
filetypes.

Switched the static list of filetypes to automatically format on save to
be replaced by automatically gathering all filetypes set up for
formatter.nvim since I want everything formatted anyway.

nvim/.config/nvim/lua/plug/_format.lua

@@ -2,22 +2,14 @@ local augroup = require('helpers.augroup')
 
 -- for each filetype autoformat on save
 -- TODO can automatically gather from formatter table keys?
-local filetypes =
-    'bash,cpp,go,html,javascript,lua,python,rust,sh,typescript,zsh'
-augroup({
-    {
-        'FileType', filetypes, 'autocmd', 'BufWritePost', '<buffer>',
-        'FormatWrite'
-    }
-}, 'formatonsave')
-
 local prettierfmt = {
     function()
+        local set_quotes = "--single-quote"
+        if vim.bo.filetype == "json" then set_quotes = "--double-quote" end
         return {
             exe = "prettier",
             args = {
-                "--stdin-filepath", vim.api.nvim_buf_get_name(0),
-                '--single-quote'
+                "--stdin-filepath", vim.api.nvim_buf_get_name(0), set_quotes
             },
             stdin = true
         }
@@ -27,9 +19,7 @@ local shfmt = {
     function() return {exe = "shfmt", args = {"-i 4"}, stdin = true} end
 }
 
-require('formatter').setup({
-    logging = false,
-    filetype = {
+local formatters = {
     bash = shfmt,
     cpp = {
         function()
@@ -44,20 +34,14 @@ require('formatter').setup({
     go = {function() return {exe = "goimports", stdin = true} end},
     html = prettierfmt,
     javascript = prettierfmt,
+    json = prettierfmt,
     lua = {
         function()
-                return {
-                    exe = "lua-format",
-                    args = {"--indent-width", 4},
-                    stdin = true
-                }
-            end
-        },
-        python = {
-            function()
-                return {exe = "black", args = {"-"}, stdin = true}
+            return
+                {exe = "lua-format", args = {"--indent-width", 4}, stdin = true}
         end
     },
+    python = {function() return {exe = "black", args = {"-"}, stdin = true} end},
     rust = {
         function()
             return {exe = "rustfmt", args = {"--emit=stdout"}, stdin = true}
@@ -67,4 +51,12 @@ require('formatter').setup({
     typescript = prettierfmt,
     zsh = shfmt
 }
-})
+
+require('formatter').setup({logging = false, filetype = formatters})
+
+-- gather filetypes to autocorrect for each activated formatter above
+local filetype = ""
+for k, _ in pairs(formatters) do filetype = filetype .. "," .. k end
+augroup({
+    {'FileType', filetype, 'autocmd', 'BufWritePost', '<buffer>', 'FormatWrite'}
+}, 'formatonsave')