Implemented #1638 / #1644: Provide a flag to ensure same file handle …

…is used after sorting.

CHANGELOG.md

@@ -12,6 +12,7 @@ Find out more about isort's release policy [here](https://pycqa.github.io/isort/
   - Implemented #1661: Added "wemake" profile.
   - Implemented #1669: Parallel (`-j`) now defaults to number of CPU cores if no value is provided.
   - Implemented #1668: Added a safeguard against accidental usage against /.
+  - Implemented #1638 / #1644: Provide a flag `--overwrite-in-place` to ensure same file handle is used after sorting.
 
 ### 5.7.0 December 30th 2020
   - Fixed #1612: In rare circumstances an extra comma is added after import and before comment.

isort/api.py

@@ -384,7 +384,10 @@ def sort_file(
                                     ):
                                         return False
                             source_file.stream.close()
-                            tmp_file.replace(source_file.path)
+                            if config.overwrite_in_place:
+                                source_file.path.write_bytes(tmp_file.read_bytes())
+                            else:
+                                tmp_file.replace(source_file.path)
                             if not config.quiet:
                                 print(f"Fixing {source_file.path}")
                     finally:

isort/main.py

@@ -207,6 +207,14 @@ def _build_arg_parser() -> argparse.ArgumentParser:
         dest="write_to_stdout",
         action="store_true",
     )
+    general_group.add_argument(
+        "--overwrite-in-place",
+        help="Tells isort to overwrite in place using the same file handle."
+        "Comes at a performance and memory usage penalty over it's standard "
+        "approach but ensures all file flags and modes stay unchanged.",
+        dest="overwrite_in_place",
+        action="store_true",
+    )
     general_group.add_argument(
         "--show-config",
         dest="show_config",

isort/settings.py

@@ -206,6 +206,7 @@ class _Config:
     follow_links: bool = True
     indented_import_headings: bool = True
     honor_case_in_force_sorted_sections: bool = False
+    overwrite_in_place: bool = False
 
     def __post_init__(self):
         py_version = self.py_version

tests/unit/test_api.py

@@ -34,6 +34,11 @@ def test_sort_file(imperfect) -> None:
     assert imperfect.read() == fixed_content
 
 
+def test_sort_file_in_place(imperfect) -> None:
+    assert api.sort_file(imperfect, overwrite_in_place=True)
+    assert imperfect.read() == fixed_content
+
+
 def test_sort_file_to_stdout(capsys, imperfect) -> None:
     assert api.sort_file(imperfect, write_to_stdout=True)
     out, _ = capsys.readouterr()

tests/unit/test_main.py

@@ -78,6 +78,7 @@ def test_parse_args():
     assert main.parse_args(["--csi"]) == {"combine_straight_imports": True}
     assert main.parse_args(["--combine-straight-imports"]) == {"combine_straight_imports": True}
     assert main.parse_args(["--dont-follow-links"]) == {"follow_links": False}
+    assert main.parse_args(["--overwrite-in-place"]) == {"overwrite_in_place": True}
 
 
 def test_ascii_art(capsys):