Compare VSCode tmp files against original

src/darker/__main__.py

@@ -125,6 +125,7 @@ def _reformat_single_file(  # pylint: disable=too-many-arguments,too-many-locals
 
     """
     src = root / relative_path
+    rev1_relative_path = _get_rev1_path(relative_path)
     edited_linenums_differ = EditedLinenumsDiffer(root, revrange)
 
     # 4. run black
@@ -156,7 +157,7 @@ def _reformat_single_file(  # pylint: disable=too-many-arguments,too-many-locals
         # 2. diff the given revision and worktree for the file
         # 3. extract line numbers in the edited to-file for changed lines
         edited_linenums = edited_linenums_differ.revision_vs_lines(
-            relative_path, rev2_isorted, context_lines
+            rev1_relative_path, rev2_isorted, context_lines
         )
         if enable_isort and not edited_linenums and rev2_isorted == rev2_content:
             logger.debug("No changes in %s after isort", src)
@@ -199,6 +200,24 @@ def _reformat_single_file(  # pylint: disable=too-many-arguments,too-many-locals
     return last_successful_reformat
 
 
+def _get_rev1_path(path: Path) -> Path:
+    """Return the relative path to the file in the old revision
+
+    This is usually the same as the relative path on the command line. But in the
+    special case of VSCode temporary files (like ``file.py.12345.tmp``), we actually
+    want to diff against the corresponding ``.py`` file instead.
+
+    """
+    if path.suffixes[-3::2] != [".py", ".tmp"]:
+        # The file name is not like `*.py.<HASH>.tmp`. Return it as such.
+        return path
+    # This is a VSCode temporary file. Drop the hash and the `.tmp` suffix to get the
+    # original file name for retrieving the previous revision to diff against.
+    path_with_hash = path.with_suffix("")
+    original_path = path_with_hash.with_suffix("")
+    return original_path
+
+
 def modify_file(path: Path, new_content: TextDocument) -> None:
     """Write new content to a file and inform the user by logging"""
     logger.info("Writing %s bytes into %s", len(new_content.string), path)

src/darker/tests/test_main.py

@@ -1,6 +1,6 @@
 """Unit tests for :mod:`darker.__main__`"""
 
-# pylint: disable=unused-argument
+# pylint: disable=unused-argument,too-many-arguments,use-dict-literal,protected-access
 
 import logging
 import re
@@ -331,6 +331,85 @@ def test_format_edited_parts_historical(git_repo, rev1, rev2, expect):
     assert list(result) == [(paths["a.py"], a_py[x[0]], a_py[x[1]]) for x in expect]
 
 
+@pytest.mark.kwparametrize(
+    dict(),
+    dict(relative_path="file.py.12345.tmp"),
+    dict(
+        rev2_content="import  modified\n\nprint( original )\n",
+        rev2_isorted="import  modified\n\nprint( original )\n",
+        expect="import modified\n\nprint( original )\n",
+    ),
+    dict(
+        rev2_content="import  original\n\nprint(modified )\n",
+        rev2_isorted="import  original\n\nprint(modified )\n",
+        expect="import  original\n\nprint(modified)\n",
+    ),
+    dict(
+        relative_path="file.py.12345.tmp",
+        rev2_content="import  modified\n\nprint( original )\n",
+        rev2_isorted="import  modified\n\nprint( original )\n",
+        expect="import modified\n\nprint( original )\n",
+    ),
+    dict(
+        relative_path="file.py.12345.tmp",
+        rev2_content="import  original\n\nprint(modified )\n",
+        rev2_isorted="import  original\n\nprint(modified )\n",
+        expect="import  original\n\nprint(modified)\n",
+    ),
+    relative_path="file.py",
+    rev1="HEAD",
+    rev2=":WORKTREE",
+    rev2_content="import  original\nprint( original )\n",
+    rev2_isorted="import  original\nprint( original )\n",
+    enable_isort=False,
+    black_config={},
+    expect="import  original\nprint( original )\n",
+)
+def test_reformat_single_file(
+    git_repo,
+    relative_path,
+    rev1,
+    rev2,
+    rev2_content,
+    rev2_isorted,
+    enable_isort,
+    black_config,
+    expect,
+):
+    """Test for ``_reformat_single_file``"""
+    git_repo.add(
+        {"file.py": "import  original\nprint( original )\n"}, commit="Initial commit"
+    )
+    result = darker.__main__._reformat_single_file(
+        git_repo.root,
+        Path(relative_path),
+        RevisionRange(rev1, rev2),
+        TextDocument(rev2_content),
+        TextDocument(rev2_isorted),
+        enable_isort,
+        black_config,
+    )
+
+    assert result.string == expect
+
+
+@pytest.mark.kwparametrize(
+    dict(path="file.py", expect="file.py"),
+    dict(path="subdir/file.py", expect="subdir/file.py"),
+    dict(path="file.py.12345.tmp", expect="file.py"),
+    dict(path="subdir/file.py.12345.tmp", expect="subdir/file.py"),
+    dict(path="file.py.tmp", expect="file.py.tmp"),
+    dict(path="subdir/file.py.tmp", expect="subdir/file.py.tmp"),
+    dict(path="file.12345.tmp", expect="file.12345.tmp"),
+    dict(path="subdir/file.12345.tmp", expect="subdir/file.12345.tmp"),
+)
+def test_get_rev1_path(path, expect):
+    """``_get_rev1_path`` drops two suffixes from ``.py.<HASH>.tmp``"""
+    result = darker.__main__._get_rev1_path(Path(path))
+
+    assert result == Path(expect)
+
+
 @pytest.mark.kwparametrize(
     dict(arguments=["--diff"], expect_stdout=A_PY_DIFF_BLACK),
     dict(arguments=["--isort"], expect_a_py=A_PY_BLACK_ISORT),
@@ -439,7 +518,7 @@ def test_main(
     expect_retval,
     root_as_cwd,
     tmp_path_factory,
-):  # pylint: disable=too-many-arguments
+):
     """Main function outputs diffs and modifies files correctly"""
     if root_as_cwd:
         cwd = git_repo.root