Run-time check for update validator signature (#723)

* Failing test
* Fix

Author: dandavison

temporalio/workflow.py

@@ -1512,6 +1512,13 @@ def _apply_to_class(
                         f"Multiple update methods found for {defn_name} "
                         f"(at least on {name} and {updates[update_defn.name].fn.__name__})"
                     )
+                elif update_defn.validator and not _parameters_identical_up_to_naming(
+                    update_defn.fn, update_defn.validator
+                ):
+                    issues.append(
+                        f"Update validator method {update_defn.validator.__name__} parameters "
+                        f"do not match update method {update_defn.fn.__name__} parameters"
+                    )
                 else:
                     updates[update_defn.name] = update_defn
 

tests/test_workflow.py

@@ -418,3 +418,26 @@ def test_workflow_init_not__init__():
     with pytest.raises(ValueError) as err:
         workflow.init(BadWorkflowInit.not__init__)
     assert "@workflow.init may only be used on the __init__ method" in str(err.value)
+
+
+class BadUpdateValidator:
+    @workflow.update
+    def my_update(self, a: str):
+        pass
+
+    @my_update.validator  # type: ignore
+    def my_validator(self, a: int):
+        pass
+
+    @workflow.run
+    async def run(self):
+        pass
+
+
+def test_workflow_update_validator_not_update():
+    with pytest.raises(ValueError) as err:
+        workflow.defn(BadUpdateValidator)
+    assert (
+        "Update validator method my_validator parameters do not match update method my_update parameters"
+        in str(err.value)
+    )