fix(s3-deployment): fails when destinationKeyPrefix is a token with…

… a long string representation (aws#22163)

We have a limitation on the length of `destinationKeyPrefix` to be no more than 104 characters. This is because it is used to tag the destination bucket, and tag keys cannot be longer than 128 characters (we prefix the prefix).

However, this validation should not apply when `destinationKeyPrefix` is a token, because in that case it's simply validating the length of the string representation of a token, which doesn't make sense.

----

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

@@ -372,8 +372,8 @@ export class BucketDeployment extends Construct {
     // the tag key limit of 128
     // '/this/is/a/random/key/prefix/that/is/a/lot/of/characters/do/we/think/that/it/will/ever/be/this/long?????'
     // better to throw an error here than wait for CloudFormation to fail
-    if (tagKey.length > 128) {
-      throw new Error('The BucketDeployment construct requires that the "destinationKeyPrefix" be <=104 characters');
+    if (!cdk.Token.isUnresolved(tagKey) && tagKey.length > 128) {
+      throw new Error('The BucketDeployment construct requires that the "destinationKeyPrefix" be <=104 characters.');
     }
 
     /*

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

@@ -1150,6 +1150,28 @@ test('throws if destinationKeyPrefix is too long', () => {
 
 });
 
+test('skips destinationKeyPrefix validation if token', () => {
+
+  // GIVEN
+  const stack = new cdk.Stack();
+  const bucket = new s3.Bucket(stack, 'Dest');
+
+  // WHEN
+  // trick the cdk into creating a very long token
+  const prefixToken = cdk.Token.asString(5, { displayHint: 'longlonglonglonglonglonglonglonglonglonglonglonglonglonglonglonglonglonglonglonglonglonglonglonglonglonglonglonglonglonglonglong' });
+  new s3deploy.BucketDeployment(stack, 'DeployWithVpc2', {
+    sources: [s3deploy.Source.asset(path.join(__dirname, 'my-website'))],
+    destinationBucket: bucket,
+    destinationKeyPrefix: prefixToken,
+    memoryLimit: 256,
+  });
+
+  Template.fromStack(stack).hasResourceProperties('Custom::CDKBucketDeployment', {
+    DestinationBucketKeyPrefix: 5,
+  });
+
+});
+
 test('bucket has multiple deployments', () => {
 
   // GIVEN