feat(s3): imported buckets can have an explicit region

However, while this set the region on the object itself, it didn't adjust the
various region-aware properties of imported buckets (e.g., regional domain
names). This change makes the regional properties of the imported bucket use the
correct region.

fixes #9556

packages/@aws-cdk/aws-s3/README.md

@@ -135,6 +135,17 @@ const byName = Bucket.fromBucketName(this, 'BucketByName', 'my-bucket');
 const byArn  = Bucket.fromBucketArn(this, 'BucketByArn', 'arn:aws:s3:::my-bucket');
 ```
 
+The bucket's region defaults to the current stack's region, but can also be explicitly set in cases where one of the bucket's
+regional properties needs to contain the correct values.
+
+```ts
+const myCrossRegionBucket = Bucket.fromBucketAttributes(this, 'CrossRegionImport', {
+  bucketArn: 'arn:aws:s3:::my-bucket',
+  region: 'us-east-1',
+});
+// myCrossRegionBucket.bucketRegionalDomainName === 'my-bucket.s3.us-east-1.amazonaws.com'
+```
+
 ### Bucket Notifications
 
 The Amazon S3 notification feature enables you to receive notifications when

packages/@aws-cdk/aws-s3/lib/bucket.ts

@@ -1125,7 +1125,7 @@ export class Bucket extends BucketBase {
    */
   public static fromBucketAttributes(scope: Construct, id: string, attrs: BucketAttributes): IBucket {
     const stack = Stack.of(scope);
-    const region = stack.region;
+    const region = attrs.region ?? stack.region;
     const urlSuffix = stack.urlSuffix;
 
     const bucketName = parseBucketName(scope, attrs);

packages/@aws-cdk/aws-s3/test/test.bucket.ts

@@ -697,6 +697,22 @@ export = {
 
       test.done();
     },
+
+    'import can explicitly set bucket region'(test: Test) {
+      const stack = new cdk.Stack(undefined, undefined, {
+        env: { region: 'us-east-1' },
+      });
+
+      const bucket = s3.Bucket.fromBucketAttributes(stack, 'ImportedBucket', {
+        bucketName: 'myBucket',
+        region: 'eu-west-1',
+      });
+
+      test.equals(bucket.bucketRegionalDomainName, `myBucket.s3.eu-west-1.${stack.urlSuffix}`);
+      test.equals(bucket.bucketWebsiteDomainName, `myBucket.s3-website-eu-west-1.${stack.urlSuffix}`);
+
+      test.done();
+    },
   },
 
   'grantRead'(test: Test) {