Revert "restore cursor to same line of code, not same line of buffer (#989)"

This reverts commit 65c5a0d9f1.

Edge cases were discovered on the pull request post merge.

plugin/black.vim

@@ -114,29 +114,7 @@ def Black():
     string_normalization=not bool(int(vim.eval("g:black_skip_string_normalization"))),
     is_pyi=vim.current.buffer.name.endswith('.pyi'),
   )
-  (cursor_line, cursor_column) = vim.current.window.cursor
+  buffer_str = '\n'.join(vim.current.buffer) + '\n'
-  cb = vim.current.buffer[:]
-  cb_bc = cb[0:cursor_line]
-  # Format all code before the cursor.
-  # Detect unclosed blocks, close them with pass.
-  last_line = cb_bc[-1]
-  if last_line.rstrip().endswith(":"):
-      cb_bc[-1] = last_line + " pass"
-  # Determine old:new cursor location mapping
-  buffer_str_before = '\n'.join(cb_bc)+'\n'
-  try:
-    new_buffer_str_before = black.format_file_contents(buffer_str_before, fast=fast, mode=mode)
-    new_cb = new_buffer_str_before.split('\n')[:-1]
-    new_cursor_line = len(new_cb)
-    new_cursor = (new_cursor_line, cursor_column)
-  except black.NothingChanged:
-    new_cursor_line = cursor_line
-    new_cursor = (new_cursor_line, cursor_column)
-  except Exception as exc:
-    print(exc)
-  # Now we know where the cursor should be
-  # when we format the entire buffer. Do it:
-  buffer_str = '\n'.join(cb) + '\n'
   try:
     new_buffer_str = black.format_file_contents(buffer_str, fast=fast, mode=mode)
   except black.NothingChanged:
@@ -144,12 +122,10 @@ def Black():
   except Exception as exc:
     print(exc)
   else:
-    # Replace the buffer
+    cursor = vim.current.window.cursor
-    new_cb = new_buffer_str.split('\n')[:-1]
+    vim.current.buffer[:] = new_buffer_str.split('\n')[:-1]
-    vim.current.buffer[:] = new_cb
-    # Restore the cursor to its rightful place
     try:
-      vim.current.window.cursor = new_cursor
+      vim.current.window.cursor = cursor
     except vim.error:
       vim.current.window.cursor = (len(vim.current.buffer), 0)
     print(f'Reformatted in {time.time() - start:.4f}s.')