# 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 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


# Traceback (ValueError)
Traceback (most recent call last):
File "/home/domdf/Python/01 GitHub Repos/03 Libraries/wordle/venv/lib/python3.8/site-packages/tox/session/cmd/run/single.py", line 41, in _evaluate
tox_env.ensure_setup(recreate=recreate)
File "/home/domdf/Python/01 GitHub Repos/03 Libraries/wordle/venv/lib/python3.8/site-packages/tox/tox_env/api.py", line 169, in ensure_setup
self.setup()
File "/home/domdf/Python/01 GitHub Repos/03 Libraries/wordle/venv/lib/python3.8/site-packages/tox/tox_env/python/runner.py", line 44, in setup
self.install_deps()
File "/home/domdf/Python/01 GitHub Repos/03 Libraries/wordle/venv/lib/python3.8/site-packages/tox/tox_env/python/runner.py", line 68, in install_deps
requirement_file_content = requirements_file.validate_and_expand()
File "/home/domdf/Python/01 GitHub Repos/03 Libraries/wordle/venv/lib/python3.8/site-packages/tox/tox_env/python/req_file.py", line 94, in validate_and_expand
raise ValueError(line)
ValueError: -r /home/domdf/Python/01 GitHub Repos/03 Libraries/wordle/tests/requirements.txt
py36: FAIL ✖ in 0.42 seconds
py36: FAIL code 2 (0.42 seconds)
evaluation failed :( (0.49 seconds)

# 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 = [i for i in re.split(r"(?<!\\)\s", line) if i]
            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"):
                        raw_path = line[len(first) + 1 :].strip()
                        unescaped_path = re.sub(r"\\(\s)", r"\1", raw_path)
                        path = Path(unescaped_path)
                        if not path.is_absolute():
                            path = ini_dir / path
                        if not path.exists():
                            raise ValueError(
                                f"requirement file path {str(path)!r} does not exist"
                            )
                        req_file = RequirementsFile(
                            path.read_text(), within_tox_ini=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