Update panic handling (#1119)

Recover panics from validation by converting to PanicError - this will
fail the update but not the WFT and will not trigger the
WorkflowPanicPolicy. Panics from update execution still propagate out
and will be handled by the task processing loop in accordance with the
WorkflowPanicPolicy.

internal/internal_update.go

@@ -326,6 +326,12 @@ func newUpdateHandler(
 
 // validate invokes the update's validation function.
 func (h *updateHandler) validate(ctx Context, input []interface{}) (err error) {
+	defer func() {
+		if p := recover(); p != nil {
+			st := getStackTraceRaw("update validator [panic]:", 7, 0)
+			err = newPanicError(fmt.Sprintf("update validator panic: %v", p), st)
+		}
+	}()
 	_, err = executeFunctionWithWorkflowContext(ctx, h.validateFn, input)
 	return err
 }

internal/internal_update_test.go

@@ -87,7 +87,7 @@ var testSDKFlags = newSDKFlags(
 	&workflowservice.GetSystemInfoResponse_Capabilities{SdkMetadata: true},
 )
 
-func TestUpdateHandlerPanicsPropagate(t *testing.T) {
+func TestUpdateHandlerPanicHandling(t *testing.T) {
 	t.Parallel()
 
 	env := &workflowEnvironmentImpl{
@@ -107,12 +107,15 @@ func TestUpdateHandlerPanicsPropagate(t *testing.T) {
 	in := UpdateInput{Name: t.Name(), Args: []interface{}{}}
 
 	t.Run("ValidateUpdate", func(t *testing.T) {
-		defer func() { require.NotNil(t, recover(), "expected a panic") }()
-		_ = interceptor.inboundInterceptor.ValidateUpdate(ctx, &in)
+		err = interceptor.inboundInterceptor.ValidateUpdate(ctx, &in)
+		var panicerr *PanicError
+		require.ErrorAs(t, err, &panicerr,
+			"panic during validate should be converted to an error to fail the update")
 	})
 	t.Run("ExecuteUpdate", func(t *testing.T) {
-		defer func() { require.NotNil(t, recover(), "expected a panic") }()
-		_, _ = interceptor.inboundInterceptor.ExecuteUpdate(ctx, &in)
+		require.Panics(t, func() {
+			_, _ = interceptor.inboundInterceptor.ExecuteUpdate(ctx, &in)
+		}, "panic during execution should be propagated to reach the WorkflowPanicPolicy")
 	})
 }