Disable template name conflict detection (#1153)

**Pull Request Checklist**
- [X] Fixes #1151
- [X] Tests added
- [X] Documentation/examples added
- [x] [Good commit messages](https://cbea.ms/git-commit/) and/or PR
title

**Description of PR**
Currently, template name conflict detection is causing a stack overflow
when run on a recursive template.

This PR removes template name conflict detection, which was added in
#1054.

---------

Signed-off-by: Alice Purcell <alicederyn@gmail.com>

examples/workflows/steps/recursive-steps.yaml

@@ -0,0 +1,33 @@
+apiVersion: argoproj.io/v1alpha1
+kind: WorkflowTemplate
+metadata:
+  name: my-workflow
+spec:
+  entrypoint: steps
+  templates:
+  - name: sub-steps
+    steps:
+    - - name: random-roll
+        template: random-roll
+    - - arguments:
+          parameters:
+          - name: input-num
+            value: '{{steps.random-roll.outputs.result}}'
+        name: recurse
+        template: sub-steps
+        when: '{{steps.random-roll.outputs.result}} != 0'
+  - name: random-roll
+    script:
+      command:
+      - python
+      image: python:3.8
+      source: |-
+        import os
+        import sys
+        sys.path.append(os.getcwd())
+        import random
+        return random.randint(0, 2)
+  - name: steps
+    steps:
+    - - name: sub-steps
+        template: sub-steps

examples/workflows/steps/recursive_steps.py

@@ -0,0 +1,22 @@
+from hera.workflows import Step, Steps, WorkflowTemplate, script
+
+
+@script(constructor="inline")
+def random_roll():
+    import random
+
+    return random.randint(0, 2)
+
+
+with WorkflowTemplate(name="my-workflow", entrypoint="steps") as w:
+    with Steps(name="sub-steps") as sub_steps:
+        random_number = random_roll()
+        Step(
+            name="recurse",
+            arguments={"input-num": random_number.result},
+            template=sub_steps,
+            when=f"{random_number.result} != 0",
+        )
+
+    with Steps(name="steps"):
+        sub_steps()

src/hera/workflows/_context.py

@@ -8,7 +8,7 @@
 from typing import List, Optional, TypeVar, Union
 
 from hera.shared import BaseMixin
-from hera.workflows.exceptions import InvalidType, TemplateNameConflict
+from hera.workflows.exceptions import InvalidType
 from hera.workflows.protocol import Subbable, TTemplate
 
 TNode = TypeVar("TNode", bound="SubNodeMixin")
@@ -102,8 +102,6 @@ def add_sub_node(self, node: Union[SubNodeMixin, TTemplate]) -> None:
             found = False
             for t in pieces[0].templates:
                 if t.name == node.template.name:
-                    if t != node.template:
-                        raise TemplateNameConflict(f"Found multiple templates with the same name: {t.name}")
                     found = True
                     break
             if not found:

src/hera/workflows/exceptions.py

@@ -26,7 +26,7 @@ class InvalidDispatchType(WorkflowsException):
 
 
 class TemplateNameConflict(WorkflowsException):
-    """Exception raised when multiple Templates are found with the same name.."""
+    """Currently unused."""
 
     ...
 

tests/test_unit/test_context.py

@@ -1,7 +1,7 @@
 import pytest
 
-from hera.workflows import DAG, Steps, WorkflowTemplate, script
-from hera.workflows.exceptions import NodeNameConflict, TemplateNameConflict
+from hera.workflows import DAG, Step, Steps, WorkflowTemplate, script
+from hera.workflows.exceptions import NodeNameConflict
 
 
 class TestContextNameConflicts:
@@ -10,24 +10,30 @@ class TestContextNameConflicts:
     and that no two Task/Step nodes have the same name.
     """
 
-    def test_conflict_on_templates_with_same_name(self):
-        """Multiple templates can't have the same name."""
-        name = "name-of-dag-and-script"
+    def test_allows_recursive_steps(self):
+        """Recursive steps should not cause an error.
 
-        @script(name=name)
-        def example():
-            print("hello")
+        See https://github.com/argoproj-labs/hera/issues/1151
+        """
 
-        with pytest.raises(TemplateNameConflict):
-            with WorkflowTemplate(name="my-workflow", entrypoint=name), DAG(name=name):
-                example()
+        @script(constructor="inline")
+        def random_roll():
+            import random
 
-        with pytest.raises(TemplateNameConflict):
-            with WorkflowTemplate(
-                name="my-workflow",
-                entrypoint=name,
-            ), Steps(name=name):
-                example()
+            return random.randint(0, 2)
+
+        with WorkflowTemplate(name="my-workflow", entrypoint="steps"):
+            with Steps(name="sub-steps") as st:
+                random_number = random_roll()
+                Step(
+                    name="recurse",
+                    arguments={"input-num": random_number.result},
+                    template=st,
+                    when=f"{random_number.result} != 0",
+                )
+
+            with Steps(name="steps"):
+                st()
 
     def test_no_conflict_on_tasks_with_different_names_using_same_template(self):
         """Task nodes can have different names for the same script template."""