From cf4f9538ba1a3375cde16fad0e78432bbb23eecd Mon Sep 17 00:00:00 2001
From: Kim K <koomen@protonmail.com>
Date: Wed, 15 May 2019 21:49:01 +0200
Subject: [PATCH] feat: Do not delete/insert comment if nothing has changed

---
 autoload/doge/comment.vim  | 27 +++++++++++++++++++++++++++
 autoload/doge/generate.vim | 24 ++++++++++++++++++------
 2 files changed, 45 insertions(+), 6 deletions(-)
 create mode 100644 autoload/doge/comment.vim

diff --git a/autoload/doge/comment.vim b/autoload/doge/comment.vim
new file mode 100644
index 00000000..00f5ab9e
--- /dev/null
+++ b/autoload/doge/comment.vim
@@ -0,0 +1,27 @@
+" ==============================================================================
+" Filename: comment.vim
+" Maintainer: Kim Koomen <koomen@protonail.com>
+" License: MIT
+" ==============================================================================
+
+let s:save_cpo = &cpoptions
+set cpoptions&vim
+
+function! doge#comment#has_changed(old_comment, new_comment) abort
+  if len(a:old_comment) != len(a:new_comment)
+    return 1
+  endif
+
+  for l:old_line in a:old_comment
+    let l:old_line_idx = index(a:old_comment, l:old_line)
+    let l:new_line = get(a:new_comment, l:old_line_idx)
+    if trim(l:old_line) !=# trim(l:new_line)
+      return 1
+    endif
+  endfor
+
+  return 0
+endfunction
+
+let &cpoptions = s:save_cpo
+unlet s:save_cpo
diff --git a/autoload/doge/generate.vim b/autoload/doge/generate.vim
index 7e94c22f..da4dbba7 100644
--- a/autoload/doge/generate.vim
+++ b/autoload/doge/generate.vim
@@ -89,7 +89,15 @@ function! doge#generate#pattern(pattern) abort
 
   if l:has_old_comment
     let l:cursor_pos = getpos('.')
-    execute(l:old_comment_start_lnum . 'd' . l:old_comment_lines_amount)
+
+    " Preserve the old comment before deleting.
+    let l:old_comment = getline(l:old_comment_start_lnum, l:old_comment_end_lnum)
+    let l:comment_has_changed = doge#comment#has_changed(l:old_comment, l:comment)
+
+    " Delete the old comment.
+    if l:comment_has_changed
+      execute(l:old_comment_start_lnum . 'd' . l:old_comment_lines_amount)
+    endif
 
     " If we have deleted a comment that is 'below' the function expression then
     " our cursor moved a line too much, so revert its position. This is the
@@ -112,11 +120,15 @@ function! doge#generate#pattern(pattern) abort
     let l:comment_lnum_inherited_indent = line('.')
   endif
 
-  " Write the comment.
-  call append(
-        \ l:comment_lnum_insert_position,
-        \ map(l:comment, {k, line -> doge#indent#line(l:comment_lnum_inherited_indent, line)})
-        \ )
+  " Write the comment if it changed.
+  if l:comment_has_changed
+    call append(
+          \ l:comment_lnum_insert_position,
+          \ map(l:comment, {k, line -> doge#indent#line(l:comment_lnum_inherited_indent, line)})
+          \ )
+  else
+    echo '[DoGE] Comment is up-to-date, skipping'
+  endif
 
   if l:has_old_comment
     call setpos('.', l:cursor_pos)