def _check_version_exists()

in gym/envs/registration.py [0:0]

• 29 lines of code
• 18 McCabe index (conditional complexity)

def _check_version_exists(ns: Optional[str], name: str, version: Optional[int]):
    """Check if an env version exists in a namespace. If it doesn't, print a helpful error message.
    This is a complete test whether an environment identifier is valid, and will provide the best available hints.

    Args:
        ns: The environment namespace
        name: The environment space
        version: The environment version

    Raises:
        DeprecatedEnv: The environment doesn't exist but a default version does
        VersionNotFound: The ``version`` used doesn't exist
        DeprecatedEnv: Environment version is deprecated
    """
    if get_env_id(ns, name, version) in registry:
        return

    _check_name_exists(ns, name)
    if version is None:
        return

    message = f"Environment version `v{version}` for environment `{get_env_id(ns, name, None)}` doesn't exist."

    env_specs = [
        spec_
        for spec_ in registry.values()
        if spec_.namespace == ns and spec_.name == name
    ]
    env_specs = sorted(env_specs, key=lambda spec_: int(spec_.version or -1))

    default_spec = [spec_ for spec_ in env_specs if spec_.version is None]

    if default_spec:
        message += f" It provides the default version {default_spec[0].id}`."
        if len(env_specs) == 1:
            raise error.DeprecatedEnv(message)

    # Process possible versioned environments

    versioned_specs = [spec_ for spec_ in env_specs if spec_.version is not None]

    latest_spec = max(versioned_specs, key=lambda spec: spec.version, default=None)  # type: ignore
    if latest_spec is not None and version > latest_spec.version:
        version_list_msg = ", ".join(f"`v{spec_.version}`" for spec_ in env_specs)
        message += f" It provides versioned environments: [ {version_list_msg} ]."

        raise error.VersionNotFound(message)

    if latest_spec is not None and version < latest_spec.version:
        raise error.DeprecatedEnv(
            f"Environment version v{version} for `{get_env_id(ns, name, None)}` is deprecated. "
            f"Please use `{latest_spec.id}` instead."
        )