# Buggy code
def validate_and_expand(self) -> List[str]:
    raw = self._normalize_raw()
    result: List[str] = []
    ini_dir = self.root
    for at, line in enumerate(raw.splitlines(), start=1):
        if line.startswith("#"):
            continue
        line = re.sub(r"\s#.*", "", line).strip()
        if not line:
            continue
        if line.startswith("-"):  # handle flags
            words = re.findall(r"\S+", line)
            first = words[0]
            if first in self.VALID_OPTIONS["no_arg"]:
                if len(words) != 1:
                    raise ValueError(line)
                else:
                    result.append(" ".join(words))
            elif first in self.VALID_OPTIONS["one_arg"]:
                if len(words) != 2:
                    raise ValueError(line)
                else:
                    if first == "-r":
                        path = Path(line[3:].strip())
                        if not path.is_absolute():
                            path = ini_dir / path
                        req_file = RequirementsFile(
                            path.read_text(), allow_short_req_file=False, root=self.root
                        )
                        result.extend(req_file.validate_and_expand())
                    else:
                        result.append(" ".join(words))
            else:
                raise ValueError(line)
        else:
            try:
                req = Requirement(line)
                result.append(str(req))
            except InvalidRequirement as exc:
                if is_url(line) or any(
                    line.startswith(f"{v}+") and is_url(line[len(v) + 1 :]) for v in VCS
                ):
                    result.append(line)
                else:
                    path = ini_dir / line
                    try:
                        is_valid_file = path.exists() and path.is_file()
                    except (
                        OSError
                    ):  # https://bugs.python.org/issue42855 # pragma: no cover
                        is_valid_file = False  # pragma: no cover
                    if not is_valid_file:
                        raise ValueError(f"{at}: {line}") from exc
                    result.append(str(path))
    return result


# Traceback (ValueError)
$ tox4 -e docs                                                                                                                  [10:45:55]
docs: internal error
Traceback (most recent call last):
File "/Users/ssbarnea/.local/pipx/venvs/tox/lib/python3.9/site-packages/tox/session/cmd/run/single.py", line 41, in _evaluate
tox_env.ensure_setup(recreate=recreate)
File "/Users/ssbarnea/.local/pipx/venvs/tox/lib/python3.9/site-packages/tox/tox_env/api.py", line 169, in ensure_setup
self.setup()
File "/Users/ssbarnea/.local/pipx/venvs/tox/lib/python3.9/site-packages/tox/tox_env/python/runner.py", line 44, in setup
self.install_deps()
File "/Users/ssbarnea/.local/pipx/venvs/tox/lib/python3.9/site-packages/tox/tox_env/python/runner.py", line 68, in install_deps
requirement_file_content = requirements_file.validate_and_expand()
File "/Users/ssbarnea/.local/pipx/venvs/tox/lib/python3.9/site-packages/tox/tox_env/python/req_file.py", line 105, in validate_and_expand
raise ValueError(line)
ValueError: -c/Users/ssbarnea/c/a/ansible-lint/docs/requirements.txt
docs: FAIL ✖ in 0.13 seconds
docs: FAIL code 2 (0.13 seconds)
evaluation failed :( (0.20 seconds)
FAIL: 2

# Fixed code
def validate_and_expand(self) -> List[str]:
    raw = self._normalize_raw()
    result: List[str] = []
    ini_dir = self.root
    for at, line in enumerate(raw.splitlines(), start=1):
        if line.startswith("#"):
            continue
        line = re.sub(r"\s#.*", "", line).strip()
        if not line:
            continue
        if line.startswith("-"):  # handle flags
            words = re.findall(r"\S+", line)
            first = words[0]
            if first in self.VALID_OPTIONS["no_arg"]:
                if len(words) != 1:
                    raise ValueError(line)
                else:
                    result.append(" ".join(words))
            elif first in self.VALID_OPTIONS["one_arg"]:
                if len(words) != 2:
                    raise ValueError(line)
                else:
                    if first in ("-r", "--requirement", "-c", "--constraint"):
                        path = Path(line[len(first) + 1 :].strip())
                        if not path.is_absolute():
                            path = ini_dir / path
                        req_file = RequirementsFile(
                            path.read_text(), allow_short_req_file=False, root=self.root
                        )
                        result.extend(req_file.validate_and_expand())
                    else:
                        result.append(" ".join(words))
            else:
                raise ValueError(line)
        else:
            try:
                req = Requirement(line)
                result.append(str(req))
            except InvalidRequirement as exc:
                if is_url(line) or any(
                    line.startswith(f"{v}+") and is_url(line[len(v) + 1 :]) for v in VCS
                ):
                    result.append(line)
                else:
                    path = ini_dir / line
                    try:
                        is_valid_file = path.exists() and path.is_file()
                    except (
                        OSError
                    ):  # https://bugs.python.org/issue42855 # pragma: no cover
                        is_valid_file = False  # pragma: no cover
                    if not is_valid_file:
                        raise ValueError(f"{at}: {line}") from exc
                    result.append(str(path))
    return result