From bf00d025095b7b7a7490a5a36be2ab7b27042283 Mon Sep 17 00:00:00 2001
From: Rico Huijbers <rix0rrr@gmail.com>
Date: Tue, 16 Feb 2021 14:36:03 +0000
Subject: [PATCH] Don't fail on a concatenated ARN

---
 packages/@aws-cdk/core/lib/resource.ts        |  5 ++-
 packages/@aws-cdk/core/lib/token.ts           | 25 +++++++++++-
 .../core/test/cross-environment-token.test.ts | 39 +++++++++++++++++++
 3 files changed, 66 insertions(+), 3 deletions(-)

diff --git a/packages/@aws-cdk/core/lib/resource.ts b/packages/@aws-cdk/core/lib/resource.ts
index a3a021715cde2..6445fe718c547 100644
--- a/packages/@aws-cdk/core/lib/resource.ts
+++ b/packages/@aws-cdk/core/lib/resource.ts
@@ -239,7 +239,10 @@ export abstract class Resource extends CoreConstruct implements IResource {
  * If the given value is NOT a Reference, just return a simple Lazy.
  */
 function mimicReference(refSource: any, producer: IStringProducer): string {
-  const reference = Tokenization.reverse(refSource);
+  const reference = Tokenization.reverse(refSource, {
+    // If this is an ARN concatenation, just fail to extract a reference.
+    failConcat: false,
+  });
   if (!Reference.isReference(reference)) {
     return Lazy.uncachedString(producer);
   }
diff --git a/packages/@aws-cdk/core/lib/token.ts b/packages/@aws-cdk/core/lib/token.ts
index f92a2560cac7c..e17227d0f8ef5 100644
--- a/packages/@aws-cdk/core/lib/token.ts
+++ b/packages/@aws-cdk/core/lib/token.ts
@@ -164,9 +164,16 @@ export class Tokenization {
    *
    * In case of a string, the string must not be a concatenation.
    */
-  public static reverse(x: any): IResolvable | undefined {
+  public static reverse(x: any, options: ReverseOptions = {}): IResolvable | undefined {
     if (Tokenization.isResolvable(x)) { return x; }
-    if (typeof x === 'string') { return Tokenization.reverseCompleteString(x); }
+    if (typeof x === 'string') {
+      if (options.failConcat === false) {
+        // Handle this specially because reverseCompleteString might fail
+        const fragments = Tokenization.reverseString(x);
+        return fragments.length === 1 ? fragments.firstToken : undefined;
+      }
+      return Tokenization.reverseCompleteString(x);
+    }
     if (Array.isArray(x)) { return Tokenization.reverseList(x); }
     if (typeof x === 'number') { return Tokenization.reverseNumber(x); }
     return undefined;
@@ -220,6 +227,20 @@ export class Tokenization {
   }
 }
 
+/**
+ * Options for the 'reverse()' operation
+ */
+export interface ReverseOptions {
+  /**
+   * Fail if the given string is a concatenation
+   *
+   * If `false`, just return `undefined`.
+   *
+   * @default true
+   */
+  readonly failConcat?: boolean;
+}
+
 /**
  * Options to the resolve() operation
  *
diff --git a/packages/@aws-cdk/core/test/cross-environment-token.test.ts b/packages/@aws-cdk/core/test/cross-environment-token.test.ts
index 9b59ac80f4729..a0d833996121c 100644
--- a/packages/@aws-cdk/core/test/cross-environment-token.test.ts
+++ b/packages/@aws-cdk/core/test/cross-environment-token.test.ts
@@ -269,6 +269,11 @@ test.each([undefined, 'SomeName'])('stack.exportValue() on name attributes with
   expect(templateA).toEqual(templateM);
 });
 
+test('can instantiate resource with constructed physicalname ARN', () => {
+  const stack = new Stack();
+  new MyResourceWithConstructedArnAttribute(stack, 'Resource');
+});
+
 class MyResource extends Resource {
   public readonly arn: string;
   public readonly name: string;
@@ -293,3 +298,37 @@ class MyResource extends Resource {
     });
   }
 }
+
+/**
+ * Some resources build their own Arn attribute by constructing strings
+ *
+ * This will be because the L1 doesn't expose a `{ Fn::GetAtt: ['Arn'] }`.
+ *
+ * They won't be able to `exportValue()` it, but it shouldn't crash.
+ */
+class MyResourceWithConstructedArnAttribute extends Resource {
+  public readonly arn: string;
+  public readonly name: string;
+
+  constructor(scope: Construct, id: string, physicalName?: string) {
+    super(scope, id, { physicalName });
+
+    const res = new CfnResource(this, 'Resource', {
+      type: 'My::Resource',
+      properties: {
+        resourceName: this.physicalName,
+      },
+    });
+
+    this.name = this.getResourceNameAttribute(res.ref.toString());
+    this.arn = this.getResourceArnAttribute(Stack.of(this).formatArn({
+      resource: 'my-resource',
+      resourceName: res.ref.toString(),
+      service: 'myservice',
+    }), {
+      resource: 'my-resource',
+      resourceName: this.physicalName,
+      service: 'myservice',
+    });
+  }
+}