chore: give every coverage pragma a reason (TS6)

eof_fixer/fixer.py

@@ -13,7 +13,7 @@
 
 def _assert_never(value: NoReturn) -> NoReturn:
     """Static-exhaustiveness guard: ty errors if any union member can reach here."""
-    raise AssertionError(value)  # pragma: no cover
+    raise AssertionError(value)  # pragma: no cover - ty proves every call unreachable (ADR-0002)
 
 
 @dataclasses.dataclass(frozen=True)
@@ -72,7 +72,7 @@ def _detect_trailing(file_obj: IO[bytes]) -> _EofAction:
         if remaining.startswith(sequence):
             return Truncate(position + len(sequence))
 
-    raise AssertionError("unreachable")  # pragma: no cover  # noqa: EM101
+    raise AssertionError("unreachable")  # noqa: EM101  # pragma: no cover - remaining is all \n/\r, so a sequence matches
 
 
 def fix_file(file_obj: IO[bytes], *, check: bool) -> bool:
@@ -99,7 +99,7 @@ def fix_file(file_obj: IO[bytes], *, check: bool) -> bool:
                 file_obj.seek(offset)
                 file_obj.truncate()
             return True
-        case _:  # pragma: no cover
+        case _:  # pragma: no cover - exhaustiveness guard; ty verifies every _EofAction is matched
             _assert_never(action)
 
 

tests/test_discovery.py

@@ -107,7 +107,7 @@ def test_ignore_rules_come_only_from_gitignore_files_in_the_tree(tmp_path: pathl
     (info / "exclude").write_text("*.log\n")
     (tmp_path / "a.log").write_text("x")
 
-    def _no_subprocess(*args: object, **kwargs: object) -> None:  # pragma: no cover
+    def _no_subprocess(*args: object, **kwargs: object) -> None:  # pragma: no cover - runs only if discovery spawns one
         message = f"discovery spawned a subprocess: {args} {kwargs}"
         raise AssertionError(message)
 
@@ -125,7 +125,7 @@ def test_symlinks_are_skipped(tmp_path: pathlib.Path) -> None:
     link = tmp_path / "link.txt"
     try:
         link.symlink_to(target)
-    except (OSError, NotImplementedError):  # pragma: no cover
+    except (OSError, NotImplementedError):  # pragma: no cover - only where the OS refuses symlinks
         pytest.skip("symlinks not available on this platform")
     result = _walk(tmp_path)
     assert "target.txt" in result

tests/test_fixer.py

@@ -151,7 +151,7 @@ def test_symlink_does_not_crash(tmp_path: pathlib.Path) -> None:
     link = tmp_path / "l.txt"
     try:
         link.symlink_to(target)
-    except (OSError, NotImplementedError):  # pragma: no cover
+    except (OSError, NotImplementedError):  # pragma: no cover - only where the OS refuses symlinks
         pytest.skip("symlinks not available on this platform")
     fixed = _names(fix_directory(tmp_path))
     assert "t.txt" in fixed