Recursive YAML generation fail (hera 5.16.1)

[gcemaj]

Pre-bug-report checklist

1. This bug can be reproduced using pure Argo YAML

• [ ] Yes 👉 Please report a bug to the Argo Workflows GitHub 👈
• [x] 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...

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

Bug report

Describe the bug Cannot generate YAML when building recursive steps, this works in hera <= 5.14.*

Error log if applicable:

  File "/.../hera/workflows/_meta_mixins.py", line 376, in __call__
    return Step(template=self, **kwargs)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/.../pydantic/v1/main.py", line 349, in __init__
    __pydantic_self__._init_private_attributes()
  File "/.../hera/shared/_global_config.py", line 181, in _init_private_attributes
    self.__hera_init__()
  File "/.../hera/workflows/_context.py", line 30, in __hera_init__
    _context.add_sub_node(self)
  File "/.../hera/workflows/_context.py", line 105, in add_sub_node
    if t != node.template:
   .
   .
   .
   .
Maximum depth exceeded...

To Reproduce Full Hera code to reproduce the bug:

from hera.expr import g
from hera.workflows import Parameter, Steps, WorkflowTemplate, Step

@script(constructor="inline")
def do(input_num: Annotated[int, Parameter(description="a number")]) -> Annotated[int, Parameter(name="output-num")]:
    return input_num - 1

def get_workflow_template() -> WorkflowTemplate:
    with WorkflowTemplate(
        name="<name>",
        entrypoint="steps",
    ) as wt:
        with Steps(name="sub-steps", inputs=[Parameter(name="input-num", value=5)]) as st:
            do_output = do(arguments={"input-num": f"{g.inputs.parameters.get('input-num'):$}"})
            Step(
                name="recurse",
                arguments={
                    "input-num": do_output.get_parameter('output-num').value,
                },
                template=st,
                when=f"{do_output.get_parameter('output-num')} <= 0",
            )

        with Steps(name="steps"):
            st(
                arguments={
                    "input-num": 10
                }
            )

        return wt

Expected behavior For the YAML to be properly generated, for this minimal example it shoudl be something like

apiVersion: argoproj.io/v1alpha1
kind: WorkflowTemplate
metadata:
  name: <name>
spec:
  entrypoint: steps
  templates:
  - inputs:
      parameters:
      - name: input-num
        value: '5'
    name: sub-steps
    steps:
    - - arguments:
          parameters:
          - name: input-num
            value: '{{inputs.parameters.input-num}}'
        name: do
        template: do
    - - arguments:
          parameters:
          - name: input-num
            value: '{{steps.do.outputs.parameters.output-num}}'
        name: recurse
        template: sub-steps
        when: '{{steps.do.outputs.parameters.output-num}} <= 0'
  - inputs:
      parameters:
      - description: a number
        name: input_num
    name: do
    outputs:
      parameters:
      - name: output-num
    script:
      command:
      - python
      image: <image>
      source: |-
        import os
        import sys
        sys.path.append(os.getcwd())
        import json
        try: input_num = json.loads(r'''{{inputs.parameters.input_num}}''')
        except: input_num = r'''{{inputs.parameters.input_num}}'''

        """Prints out a message."""
        return input_num - 1
  - name: steps
    steps:
    - - arguments:
          parameters:
          - name: input-num
            value: '10'
        name: sub-steps
        template: sub-steps

Environment

• Hera Version: 5.16.1
• Python Version: 3.10
• Argo Version: 3.X.X

Additional context Add any other context about the problem here.

[alicederyn]

Looks like this issue was introduced in https://github.com/argoproj-labs/hera/pull/1054 (merged in 5.16.0)