[Step Function] 8.1 Fix subscription filter creation failure

serverless/src/step_function/forwarder.ts

@@ -11,9 +11,10 @@ export const SUBSCRIPTION_FILTER_PREFIX = "LogGroupDatadogSubscriptionFilter";
  */
 export function addForwarder(resources: Resources, config: Configuration, stateMachine: StateMachine): void {
   log.debug(`Subscribing the forwarder to the log group...`);
-  const logGroup = findLogGroup(resources, stateMachine);
+  const [logGroupKey, logGroup] = findLogGroup(resources, stateMachine);
   const subscriptionFilter = {
     Type: "AWS::Logs::SubscriptionFilter",
+    DependsOn: logGroupKey,
     Properties: {
       LogGroupName: logGroup.Properties.LogGroupName,
       DestinationArn: config.stepFunctionForwarderArn,

serverless/src/step_function/log.ts

@@ -168,8 +168,9 @@ export const buildLogGroupName = (stateMachine: StateMachine, env: string | unde
  *    "Fn::GetAtt": ["MyStateMachineLogGroup", "Arn"]
  *    which is the most common way of referencing a log group.
  * We can add support for other cases when users request it.
+ * @returns [logGroupKey, logGroup]
  */
-export function findLogGroup(resources: Resources, stateMachine: StateMachine): LogGroup {
+export function findLogGroup(resources: Resources, stateMachine: StateMachine): [string, LogGroup] {
   const logConfig = stateMachine.properties.LoggingConfiguration;
 
   if (!logConfig?.Destinations) {
@@ -189,5 +190,5 @@ export function findLogGroup(resources: Resources, stateMachine: StateMachine):
   }
   const logGroupKey = logGroupArn[FN_GET_ATT][0];
   const logGroup = resources[logGroupKey];
-  return logGroup;
+  return [logGroupKey, logGroup];
 }

serverless/test/step_function/forwarder.spec.ts

@@ -13,17 +13,21 @@ describe("addForwarder", () => {
     const stateMachine = {
       resourceKey: "MyStateMachine",
     } as any;
-    (findLogGroup as jest.Mock).mockReturnValue({
-      Properties: {
-        LogGroupName: "/aws/lambda/my-function",
+    (findLogGroup as jest.Mock).mockReturnValue([
+      "MyStateMachineLogGroup",
+      {
+        Properties: {
+          LogGroupName: "/aws/lambda/my-function",
+        },
       },
-    });
+    ]);
 
     addForwarder(resources, config, stateMachine);
 
     const subscriptionFilterKey = stateMachine.resourceKey + SUBSCRIPTION_FILTER_PREFIX;
     expect(resources[subscriptionFilterKey]).toEqual({
       Type: "AWS::Logs::SubscriptionFilter",
+      DependsOn: "MyStateMachineLogGroup",
       Properties: {
         LogGroupName: "/aws/lambda/my-function",
         DestinationArn: config.stepFunctionForwarderArn,

serverless/test/step_function/log.spec.ts

@@ -174,7 +174,8 @@ describe("findLogGroup", () => {
       },
     };
 
-    const logGroup = findLogGroup(resources, stateMachine);
+    const [logGroupKey, logGroup] = findLogGroup(resources, stateMachine);
+    expect(logGroupKey).toBe("MyStateMachineLogGroup");
     expect(logGroup.Type).toBe("AWS::Logs::LogGroup");
     expect(logGroup.Properties.LogGroupName).toBe("/aws/vendedlogs/states/MyStateMachine-Logs-dev");
   });