fix(middleware-sdk-rds): stop throw when source id key is optional (#2770)

Author: AllanZhengYP

packages/middleware-sdk-rds/src/index.ts

@@ -17,18 +17,10 @@ import { formatUrl } from "@aws-sdk/util-format-url";
 
 const regARN = /arn:[\w+=/,.@-]+:[\w+=/,.@-]+:([\w+=/,.@-]*)?:[0-9]+:[\w+=/,.@-]+(:[\w+=/,.@-]+)?(:[\w+=/,.@-]+)?/;
 
-const sourceIds: string[] = [
-  "SourceDBSnapshotIdentifier",
-  "SourceDBInstanceIdentifier",
-  "ReplicationSourceIdentifier",
-  "SourceDBClusterSnapshotIdentifier",
-  "SourceDBInstanceArn",
-];
-
 const sourceIdToCommandKeyMap: { [key: string]: string } = {
   SourceDBSnapshotIdentifier: "CopyDBSnapshot",
   SourceDBInstanceIdentifier: "CreateDBInstanceReadReplica",
-  ReplicationSourceIdentifier: "CreateDBCluster",
+  ReplicationSourceIdentifier: "CreateDBCluster", // This key is optional.
   SourceDBClusterSnapshotIdentifier: "CopyDBClusterSnapshot",
   SourceDBInstanceArn: "StartDBInstanceAutomatedBackupsReplication",
 };
@@ -47,24 +39,20 @@ interface PreviouslyResolved {
  * Config of the middleware to automatically add presigned URL to request.
  * The presigned URL is generated by sigV4
  */
-
 export function crossRegionPresignedUrlMiddleware(options: PreviouslyResolved): InitializeMiddleware<any, any> {
   return <Output extends MetadataBearer>(next: InitializeHandler<any, Output>): InitializeHandler<any, Output> =>
     async (args: InitializeHandlerArguments<any>): Promise<InitializeHandlerOutput<Output>> => {
       const { input } = args;
       const region = await options.region();
-      let command, sourceId;
-      for (const id of sourceIds) {
-        if (input.hasOwnProperty(id)) {
-          sourceId = id;
-          command = sourceIdToCommandKeyMap[id];
-        }
-      }
-      if (!sourceId) {
-        throw new Error("Source identifier key not set");
-      }
-      if (!input.PreSignedUrl && isARN(input[sourceId]) && region !== getEndpointFromARN(input[sourceId])) {
-        const sourceRegion = getEndpointFromARN(input[sourceId]);
+      const sourceIdKey = Object.keys(sourceIdToCommandKeyMap).filter((sourceKeyId) =>
+        input.hasOwnProperty(sourceKeyId)
+      )[0];
+      // Source id is optional.
+      if (!sourceIdKey) return next(args);
+
+      const command = sourceIdToCommandKeyMap[sourceIdKey];
+      if (!input.PreSignedUrl && isARN(input[sourceIdKey]) && region !== getEndpointFromARN(input[sourceIdKey])) {
+        const sourceRegion = getEndpointFromARN(input[sourceIdKey]);
         const resolvedEndpoint = await options.endpoint();
         resolvedEndpoint.hostname = `rds.${sourceRegion}.amazonaws.com`;
         const request = new HttpRequest({
@@ -78,7 +66,7 @@ export function crossRegionPresignedUrlMiddleware(options: PreviouslyResolved):
             Version: version,
             KmsKeyId: input.KmsKeyId,
             DestinationRegion: region,
-            [sourceId]: input[sourceId],
+            [sourceIdKey]: input[sourceIdKey],
           },
         });
         const signer = new SignatureV4({