fix(formatter): Avoid rewriting the file if it has not been changed

We use djLint as part of treefmt [1] to reformat HTML templates
tree-wide, and treefmt looks at file modification time to determine
if it was reformatted or not. And with --fail-on-change option
passed, it exits with status 1 when it thinks files are modified.

This patch makes djLint not rewrite the file if there are no changes
to write back, which makes treefmt --fail-on-change do the right
thing.

[1]: https://github.com/numtide/treefmt

src/djlint/reformat.py

@@ -52,7 +52,9 @@ def reformat_file(config: Config, this_file: Path) -> dict:
 
     beautified_code = formatter(config, rawcode)
 
-    if config.check is not True or config.stdin is True:
+    if (
+        config.check is not True and beautified_code != rawcode
+    ) or config.stdin is True:
         this_file.write_bytes(beautified_code.encode("utf8"))
 
     out = {

tests/test_djlint/test_djlint.py

@@ -23,6 +23,7 @@
 
 
 # pylint: disable=C0116
+from os.path import getmtime
 from pathlib import Path
 from typing import TextIO
 
@@ -174,6 +175,16 @@ def test_reformatter_simple_error(runner: CliRunner, tmp_file: TextIO) -> None:
     assert "1 file was updated." in result.output
 
 
+def test_reformatter_no_error(runner: CliRunner, tmp_file: TextIO) -> None:
+    write_to_file(tmp_file.name, b"<div>\n    <p>nice stuff here</p>\n</div>\n")
+    old_mtime = getmtime(tmp_file.name)
+    result = runner.invoke(djlint, [tmp_file.name, "--reformat"])
+    assert result.exit_code == 0
+    assert "0 files were updated." in result.output
+    new_mtime = getmtime(tmp_file.name)
+    assert new_mtime == old_mtime
+
+
 def test_check_reformatter_simple_error_quiet(
     runner: CliRunner, tmp_file: TextIO
 ) -> None: