fix(workflows): require a cases block on switch steps

src/specify_cli/workflows/steps/switch/__init__.py

@@ -96,6 +96,19 @@ def validate(self, config: dict[str, Any]) -> list[str]:
                 f"Switch step {config.get('id', '?')!r} is missing "
                 f"'expression' field."
             )
+        # Every other control-flow step requires its branch payload: ``if``
+        # requires ``then``, ``fan-out`` requires ``items`` and ``step``,
+        # ``fan-in`` a non-empty ``wait_for``, ``gate`` a ``message``. Without
+        # the same check, a switch whose ``cases:`` block is missing or mistyped
+        # (``case:`` is the obvious slip) validates clean and then reports
+        # COMPLETED with ``matched_case: "__default__"`` -- a default it may not
+        # even declare -- having dispatched nothing. That is the "silent empty
+        # result + COMPLETED" wiring bug the fan-in guard exists to prevent.
+        if "cases" not in config:
+            errors.append(
+                f"Switch step {config.get('id', '?')!r} is missing "
+                f"'cases' field."
+            )
         cases = config.get("cases", {})
         if not isinstance(cases, dict):
             errors.append(

tests/test_workflows.py

@@ -3309,6 +3309,38 @@ def test_validate_missing_expression(self):
         errors = step.validate({"id": "test", "cases": {}})
         assert any("missing 'expression'" in e for e in errors)
 
+    def test_validate_missing_cases(self):
+        """`cases` is the switch's branch payload and must be required.
+
+        Every other control-flow step requires its own: `if` requires `then`,
+        `fan-out` requires `items` and `step`, `fan-in` a non-empty `wait_for`,
+        `gate` a `message`. Without it, a `case:` typo validated clean and then
+        reported COMPLETED with `matched_case: "__default__"` having dispatched
+        nothing.
+        """
+        from specify_cli.workflows.steps.switch import SwitchStep
+
+        step = SwitchStep()
+
+        # Absent entirely.
+        errors = step.validate({"id": "route", "expression": "{{ inputs.x }}"})
+        assert any("missing 'cases'" in e for e in errors), errors
+
+        # The realistic slip: `case:` instead of `cases:`.
+        errors = step.validate(
+            {"id": "route", "expression": "{{ inputs.x }}", "case": {"a": []}}
+        )
+        assert any("missing 'cases'" in e for e in errors), errors
+
+    def test_validate_accepts_an_empty_cases_mapping(self):
+        """An explicitly declared but empty `cases:` is still a declaration."""
+        from specify_cli.workflows.steps.switch import SwitchStep
+
+        errors = SwitchStep().validate(
+            {"id": "route", "expression": "{{ inputs.x }}", "cases": {}}
+        )
+        assert not any("missing 'cases'" in e for e in errors), errors
+
     def test_validate_invalid_cases_and_default(self):
         from specify_cli.workflows.steps.switch import SwitchStep