feat: add undojoin as a format option (#488)

* feat: add new format option: undojoin

This option allow user to automatically perform undojoin command before
formatting. This is useful if the user uses an autosave plugin + format
on save, because in case of undo, it will undo the last change AND the
formatting. Without this option, it will only undo the formatting.

* fix: passed linting

* fix: apply undojoin for LSP formatting

* doc: fix type annotations for apply_format

* doc: regenerate documentation

---------

Co-authored-by: Steven Arcangeli <stevearc@stevearc.com>

1 files changed, 19 insertions, 3 deletions

diff --git a/lua/conform/runner.lua b/lua/conform/runner.lua
index c0a19cd..333c16f 100644
--- a/lua/conform/runner.lua
+++ b/lua/conform/runner.lua
@@ -9,6 +9,7 @@ local M = {}
 ---@class (exact) conform.RunOpts
 ---@field exclusive boolean If true, ensure only a single formatter is running per buffer
 ---@field dry_run boolean If true, do not apply changes and stop after the first formatter attempts to do so
+---@field undojoin boolean Use undojoin to merge formatting changes with previous edit
 
 ---@param formatter_name string
 ---@param ctx conform.Context
@@ -168,8 +169,18 @@ end
 ---@param new_lines string[]
 ---@param range? conform.Range
 ---@param only_apply_range boolean
+---@param dry_run boolean
+---@param undojoin boolean
 ---@return boolean any_changes
-M.apply_format = function(bufnr, original_lines, new_lines, range, only_apply_range, dry_run)
+M.apply_format = function(
+  bufnr,
+  original_lines,
+  new_lines,
+  range,
+  only_apply_range,
+  dry_run,
+  undojoin
+)
   if bufnr == 0 then
     bufnr = vim.api.nvim_get_current_buf()
   end
@@ -251,6 +262,9 @@ M.apply_format = function(bufnr, original_lines, new_lines, range, only_apply_ra
 
   if not dry_run then
     log.trace("Applying text edits: %s", text_edits)
+    if undojoin then
+      vim.cmd.undojoin()
+    end
     vim.lsp.util.apply_text_edits(text_edits, bufnr, "utf-8")
     log.trace("Done formatting %s", bufname)
   end
@@ -535,7 +549,8 @@ M.format_async = function(bufnr, formatters, range, opts, callback)
           output_lines,
           range,
           not all_support_range_formatting,
-          opts.dry_run
+          opts.dry_run,
+          opts.undojoin
         )
       end
       callback(err, did_edit)
@@ -609,7 +624,8 @@ M.format_sync = function(bufnr, formatters, timeout_ms, range, opts)
     final_result,
     range,
     not all_support_range_formatting,
-    opts.dry_run
+    opts.dry_run,
+    opts.undojoin
   )
   return err, did_edit
 end