fix(format): add config defaults and proper type hints

lua/util.lua

@@ -88,22 +88,22 @@ end
 ---| '"in_place"'
 
 ---@class ow.FormatOptions
----@field buf integer Buffer to apply formatting to
+---@field buf? integer Buffer to apply formatting to
 ---@field cmd string[] Command to run. The following keywords get replaces by the specified values:
----                    * %file%         - path to the current file
+---                    * %file%         - path to the file for `buf`
----                    * %filename%     - name of the current file
+---                    * %filename%     - name of the file for `buf`
 ---                    * %row_start%    - first row of selection
 ---                    * %row_end%      - last row of selection
 ---                    * %col_start%    - first column position of selection
 ---                    * %col_end%      - last column position of selection
 ---                    * %byte_start%   - byte count of first cell in selection
 ---                    * %byte_end%     - byte count of last cell in selection
----@field output OutputStream What stream to use as the result. May be one of `stdout`, `stderr` or `in_place`.
+---@field output? OutputStream What stream to use as the result. May be one of `stdout`, `stderr` or `in_place`.
----@field auto_indent boolean Perform auto indent on formatted range
+---@field auto_indent? boolean Perform auto indent on formatted range
----@field only_selection boolean Only send the selected lines to `stdin`
+---@field only_selection? boolean Only send the selected lines to `stdin`
----@field ignore_ret boolean Ignore non-zero return codes
+---@field ignore_ret? boolean Ignore non-zero return codes
----@field ignore_stderr boolean Ignore stderr output when not using stderr for output
+---@field ignore_stderr? boolean Ignore stderr output when not using stderr for output
----@field env table<string, string> Map of environment variables
+---@field env? table<string, string> Map of environment variables
 local FormatOptions = {}
 FormatOptions.__index = FormatOptions
 
@@ -111,17 +111,17 @@ function FormatOptions.from_opts(opts)
     return setmetatable({
         buf = opts.buf or vim.api.nvim_get_current_buf(),
         cmd = opts.cmd,
-        output = opts.output,
+        output = opts.output or "stdout",
         auto_indent = opts.auto_indent or false,
         only_selection = opts.only_selection or false,
-        ignore_ret = opts.ignore_ret,
+        ignore_ret = opts.ignore_ret or false,
-        ignore_stderr = opts.ignore_stderr,
+        ignore_stderr = opts.ignore_stderr or false,
         env = opts.env,
     }, FormatOptions)
 end
 
 --- Format buffer
----@param opts table
+---@param opts ow.FormatOptions
 function Util.format(opts)
     opts = FormatOptions.from_opts(opts)