fix(cfn-include): no longer concatenate elements of Fn::Join without tokens (#9476)

Fn.join() has some logic inside of it to simplify the expressions to concatenate the
array elements that do not contain any Tokens inside of them.
We don't want to do it in cfn-include though,
as that causes a diff from the original template.
So, wrap the array given as the second argument to Fn::Join into a Token,
to prevent the concatenation logic from triggering.

----

*By submitting this pull request, I confirm that my contribution is made under the terms of the Apache-2.0 license*

Author: skinny85

packages/@aws-cdk/cloudformation-include/test/test-templates/user-data.json

@@ -0,0 +1,30 @@
+{
+  "Resources": {
+    "LaunchConfig": {
+      "Type" : "AWS::AutoScaling::LaunchConfiguration",
+      "Properties": {
+        "ImageId": "ami-01e24be29428c15b2",
+        "InstanceType": "t1.micro",
+        "UserData": {
+          "Fn::Base64": {
+            "Fn::Join": ["", [
+              "#!/bin/bash -xe\n",
+              "yum update -y aws-cfn-bootstrap\n",
+
+              "/opt/aws/bin/cfn-init -v ",
+              "         --stack ", { "Ref" : "AWS::StackName" },
+              "         --resource LaunchConfig ",
+              "         --configsets wordpress_install ",
+              "         --region ", { "Ref" : "AWS::Region" }, "\n",
+
+              "/opt/aws/bin/cfn-signal -e $? ",
+              "         --stack ", { "Ref" : "AWS::StackName" },
+              "         --resource WebServerGroup ",
+              "         --region ", { "Ref" : "AWS::Region" }, "\n"
+            ]]
+          }
+        }
+      }
+    }
+  }
+}

packages/@aws-cdk/cloudformation-include/test/valid-templates.test.ts

@@ -184,6 +184,14 @@ describe('CDK Include', () => {
     );
   });
 
+  test('can ingest a UserData script, and output it unchanged', () => {
+    includeTestTemplate(stack, 'user-data.json');
+
+    expect(stack).toMatchTemplate(
+      loadTestFileToJsObject('user-data.json'),
+    );
+  });
+
   test('can ingest a template with intrinsic functions and conditions, and output it unchanged', () => {
     includeTestTemplate(stack, 'functions-and-conditions.json');
 

packages/@aws-cdk/core/lib/cfn-parse.ts

@@ -7,6 +7,7 @@ import {
 } from './cfn-resource-policy';
 import { CfnTag } from './cfn-tag';
 import { ICfnFinder } from './from-cfn';
+import { Lazy } from './lazy';
 import { CfnReference } from './private/cfn-reference';
 import { IResolvable } from './resolvable';
 import { isResolvableObject, Token } from './token';
@@ -359,7 +360,11 @@ export class CfnParser {
         // where the first element is the delimiter,
         // and the second is the list of elements to join
         const value = this.parseValue(object[key]);
-        return Fn.join(value[0], value[1]);
+        // wrap the array as a Token,
+        // as otherwise Fn.join() will try to concatenate
+        // the non-token parts,
+        // causing a diff with the original template
+        return Fn.join(value[0], Lazy.listValue({ produce: () => value[1] }));
       }
       case 'Fn::Cidr': {
         const value = this.parseValue(object[key]);