Allow fixit error to be ignored inline

This is necessary as a workaround to a bug in fixit
(Instagram/Fixit#405).

CHANGELOG.md

@@ -6,6 +6,21 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/).
 
 ## Unreleased
 
+### Added
+
+- Silence `fixit` errors with *inline* comments.
+
+  `fixit` does not always respect `lint-fixme` comments when they are on the
+  line above the line causing the error. This is a known bug and is reported
+  in https://github.com/Instagram/Fixit/issues/405.
+
+  In some of these cases (e.g. decorators), placing the comment on the same line
+  as the error can ensure it is respected. The `fixme-inline` linter option
+  allows the comments to be added inline instead of on the lien above.
+
+  N.B. This might prevent the comments from being successfully removed by the
+  `fix fixit` command, if there are other errors ignored on the same line.
+
 ## 1.1.0 (2023-11-24)
 
 ### Added

silence_lint_error/silence_lint_error.py

@@ -114,6 +114,28 @@ def silence_violations(
         return ''.join(new_lines)
 
 
+class FixitInline(Fixit):
+    """An alternative `fixit` implementation that adds `lint-fixme` comment inline.
+
+    This is sometimes necessary because `fixit` does not always respect `lint-fixme`
+    comments when they are on the line above the line causing the error. This is a
+    known bug and is reported in https://github.com/Instagram/Fixit/issues/405.
+
+    In some of these cases, placing the comment on the same line as the error can
+    ensure it is respected (e.g. for decorators).
+    """
+
+    def silence_violations(
+        self, src: str, violations: Sequence[Violation],
+    ) -> str:
+        [rule_name] = {violation.rule_name for violation in violations}
+        linenos_to_silence = {violation.lineno for violation in violations}
+        return comments.add_error_silencing_comments(
+            src, linenos_to_silence,
+            'lint-fixme', rule_name,
+        )
+
+
 class Flake8:
     name = 'flake8'
 
@@ -193,6 +215,7 @@ def silence_violations(
 
 LINTERS: dict[str, type[Linter]] = {
     'fixit': Fixit,
+    'fixit-inline': FixitInline,
     'flake8': Flake8,
     'ruff': Ruff,
 }

tests/silence_lint_error/fixit_test.py

@@ -139,6 +139,42 @@ def f(x):
 """
 
 
+def test_main_inline(tmp_path: Path, capsys: pytest.CaptureFixture[str]):
+    python_module = tmp_path / 't.py'
+    python_module.write_text(
+        """\
+x = None
+isinstance(x, str) or isinstance(x, int)
+
+def f(x):
+    return isinstance(x, str) or isinstance(x, int)
+""",
+    )
+
+    ret = main(
+        ('fixit-inline', 'fixit.rules:CollapseIsinstanceChecks', str(python_module)),
+    )
+
+    assert ret == 1
+    assert python_module.read_text() == """\
+x = None
+isinstance(x, str) or isinstance(x, int)  # lint-fixme: CollapseIsinstanceChecks
+
+def f(x):
+    return isinstance(x, str) or isinstance(x, int)  # lint-fixme: CollapseIsinstanceChecks
+"""  # noqa: B950
+
+    captured = capsys.readouterr()
+    assert captured.out == f"""\
+{python_module}
+"""
+    assert captured.err == """\
+-> finding errors with fixit
+found errors in 1 files
+-> adding comments to silence errors
+"""
+
+
 def test_main_no_violations(
         tmp_path: Path, capsys: pytest.CaptureFixture[str],
 ):