Support Literal types in script runner

[alicederyn]

Pre-bug-report checklist

1. This bug can be reproduced using pure Argo YAML

• Yes 👉 Please report a bug to the Argo Workflows GitHub 👈
• No

If yes, it is more likely to be an Argo bug unrelated to Hera. Please double check before submitting an issue to Hera.

2. This bug occurs in Hera when...

• exporting to YAML
• submitting to Argo
• running on Argo with the Hera runner
• other:

Bug report

Describe the bug
A clear and concise description of what the bug is:

Using a function with a Literal argument in the runner results in the following trace:

Error log if applicable:

Traceback (most recent call last):
  File "/.../python3.9/runpy.py", line 197, in _run_module_as_main
    return _run_code(code, main_globals, None,
  File ".../python3.9/runpy.py", line 87, in _run_code
    exec(code, run_globals)
  File ".../python3.9/site-packages/hera/workflows/runner.py", line 6, in <module>
    _run()
  File "/.../python3.9/site-packages/hera/workflows/_runner/util.py", line 254, in _run
    result = _runner(args.entrypoint, kwargs_list)
  File ".../python3.9/site-packages/hera/workflows/_runner/util.py", line 228, in _runner
    return function(**kwargs)
  File ".../python3.9/site-packages/hera/workflows/_runner/util.py", line 58, in inner
    filtered_kwargs = {key: _parse(value, key, f) for key, value in kwargs.items() if _is_kwarg_of(key, f)}
  File ".../python3.9/site-packages/hera/workflows/_runner/util.py", line 58, in <dictcomp>
    filtered_kwargs = {key: _parse(value, key, f) for key, value in kwargs.items() if _is_kwarg_of(key, f)}
  File ".../python3.9/site-packages/hera/workflows/_runner/util.py", line 89, in _parse
    if _is_str_kwarg_of(key, f) or _is_artifact_loaded(key, f) or _is_output_kwarg(key, f):
  File ".../python3.9/site-packages/hera/workflows/_runner/util.py", line 142, in _is_str_kwarg_of
    return issubclass(type_, str)
TypeError: issubclass() arg 1 must be a class

To Reproduce
Full Hera code to reproduce the bug:

from typing import Literal
from hera.workflows import Workflow, script

@script(constructor="runner", image="my-image")
def literal_str(my_str: Literal["foo", "bar"]):
    print(my_str)

with Workflow(name="my-workflow", entrypoint="steps") as w:
    with Steps(name="steps"):
        literal_str(arguments={"my_str": "foo"})

Expected behavior
A clear and concise description of what you expected to happen:

• For unsupported types, the error should indicate which argument had the issue, and that it is due to an unsupported type; at the moment, the key is lost, and the error message is not obvious.
• Ideally:
  • no error
  • _is_str_kwarg_of should return True
  • Parameter.enum should be inferred to be ["foo", "bar"]

Environment

• Hera Version: 5.16.2
• Python Version: 3.9.18
• Argo Version: 3.4.16.7