feat!: merge configs in conform.formatters with defaults (#140)

This breaking change should make it significantly easier to modify formatters. While I expect 99% of configs to be backwards-compatible, this can still potentially cause problems. If you:

* define a formatter in the `formatters` option
* that has the same name as a built-in formatter
* and omits a property from the original formatter (e.g. leaves out `range_args` or `cwd`)

Then you may encounter breaking behavior from this commit, because now your config definition will be merged with the built-in definition, and so will inherit those omitted properties. This config merging behavior can be opted-out of by adding `inherit = false` to your formatter config.

1 files changed, 11 insertions, 0 deletions

diff --git a/lua/conform/util.lua b/lua/conform/util.lua
index 8a0073a..bbb711a 100644
--- a/lua/conform/util.lua
+++ b/lua/conform/util.lua
@@ -156,6 +156,17 @@ M.add_formatter_args = function(formatter, extra_args, opts)
   end
 end
 
+---@param config conform.FormatterConfig
+---@param override conform.FormatterConfigOverride
+---@return conform.FormatterConfig
+M.merge_formatter_configs = function(config, override)
+  local ret = vim.tbl_deep_extend("force", config, override)
+  if override.prepend_args then
+    M.add_formatter_args(ret, override.prepend_args, { append = false })
+  end
+  return ret
+end
+
 ---@param bufnr integer
 ---@return integer
 M.buf_get_changedtick = function(bufnr)