feat: allow to create a version from an arn

This commit allows to reference a lambda from a different region and use
that as function association.

packages/@aws-cdk/aws-cloudfront/lib/web_distribution.ts

@@ -365,7 +365,7 @@ export interface LambdaFunctionAssociation {
   /**
    * A version of the lambda to associate or a resolvable resource
    */
-  readonly lambdaFunction: lambda.IVersion | cdk.IResolvable;
+  readonly lambdaFunction: lambda.IVersion;
 }
 
 export enum LambdaEdgeEventType {
@@ -719,10 +719,6 @@ export class CloudFrontWebDistribution extends cdk.Construct implements IDistrib
   }
 
   private toBehavior(input: BehaviorWithOrigin, protoPolicy?: ViewerProtocolPolicy) {
-    function isResolvable(resolvableOrVersion: cdk.IResolvable | lambda.IVersion): resolvableOrVersion is cdk.IResolvable {
-      return Boolean((resolvableOrVersion as cdk.IResolvable).resolve);
-    }
-
     let toReturn = {
       allowedMethods: this.METHOD_LOOKUP_MAP[input.allowedMethods || CloudFrontAllowedMethods.GET_HEAD],
       cachedMethods: this.METHOD_LOOKUP_MAP[input.cachedMethods || CloudFrontAllowedCachedMethods.GET_HEAD],
@@ -745,12 +741,6 @@ export class CloudFrontWebDistribution extends cdk.Construct implements IDistrib
             if (!fna.lambdaFunction) {
               return undefined;
             }
-            if (isResolvable(fna.lambdaFunction)) {
-              return {
-                eventType: fna.eventType,
-                lambdaFunctionArn: fna.lambdaFunction,
-              };
-            }
             return {
               eventType: fna.eventType,
               lambdaFunctionArn: fna.lambdaFunction.versionArn,

packages/@aws-cdk/aws-cloudfront/package.json

@@ -72,6 +72,7 @@
   },
   "dependencies": {
     "@aws-cdk/aws-certificatemanager": "^0.34.0",
+    "@aws-cdk/aws-cloudformation": "^0.34.0",
     "@aws-cdk/aws-iam": "^0.34.0",
     "@aws-cdk/aws-kms": "^0.34.0",
     "@aws-cdk/aws-lambda": "^0.34.0",
@@ -81,6 +82,7 @@
   "homepage": "https://github.com/awslabs/aws-cdk",
   "peerDependencies": {
     "@aws-cdk/aws-certificatemanager": "^0.34.0",
+    "@aws-cdk/aws-cloudformation": "^0.34.0",
     "@aws-cdk/aws-iam": "^0.34.0",
     "@aws-cdk/aws-kms": "^0.34.0",
     "@aws-cdk/aws-lambda": "^0.34.0",

packages/@aws-cdk/aws-cloudfront/test/test.basic.ts

@@ -1,4 +1,5 @@
 import { expect, haveResource } from '@aws-cdk/assert';
+import * as cloudformation from '@aws-cdk/aws-cloudformation';
 import * as lambda from '@aws-cdk/aws-lambda';
 import * as s3 from '@aws-cdk/aws-s3';
 import * as cdk from '@aws-cdk/cdk';
@@ -327,14 +328,15 @@ export = {
     const stack = new cdk.Stack();
     const sourceBucket = new s3.Bucket(stack, 'Bucket');
 
-    const lambdaFunction = new lambda.Function(stack, 'Lambda', {
+    const lambdaFunction = new lambda.SingletonFunction(stack, 'Lambda', {
+      uuid: 'xxxx-xxxx-xxxx-xxxx',
       code: lambda.Code.inline('foo'),
       handler: 'index.handler',
       runtime: lambda.Runtime.Nodejs810
     });
 
-    const lambdaVersion = new lambda.Version(stack, 'LambdaVersion', {
-      lambda: lambdaFunction
+    const customResource = new cloudformation.CustomResource(stack, 'CustomResource', {
+      provider: cloudformation.CustomResourceProvider.lambda(lambdaFunction)
     });
 
     new CloudFrontWebDistribution(stack, 'AnAmazingWebsiteProbably', {
@@ -348,7 +350,11 @@ export = {
               isDefaultBehavior: true,
               lambdaFunctionAssociations: [{
                 eventType: LambdaEdgeEventType.OriginRequest,
-                lambdaFunction: cdk.Token.asAny(lambdaVersion.versionArn)
+                lambdaFunction: lambda.Version.fromVersionArn(
+                  stack,
+                  'LambdaEdgeVersion',
+                  customResource.getAtt('Output').toString()
+                )
               }]
             }
           ]
@@ -394,7 +400,7 @@ export = {
             {
               "EventType": "origin-request",
               "LambdaFunctionARN": {
-                "Ref": "LambdaVersionFA49E61E"
+                "Fn::GetAtt": ["CustomResource", "Output"]
               }
             }
           ]

packages/@aws-cdk/aws-lambda/lib/lambda-version.ts

@@ -1,4 +1,5 @@
-import { Construct, IResource, Resource } from '@aws-cdk/cdk';
+import { Construct, Fn, IResource, Resource } from '@aws-cdk/cdk';
+import { Function } from './function';
 import { IFunction } from './function-base';
 import { CfnVersion } from './lambda.generated';
 
@@ -82,10 +83,24 @@ export interface VersionAttributes {
  */
 export class Version extends Resource implements IVersion {
 
+  /**
+   * @param scope The cdk scope creating this resource
+   * @param id The cdk id of this resource
+   * @param versionArn The version ARN to create this version from
+   */
+  public static fromVersionArn(scope: Construct, id: string, versionArn: string): IVersion {
+    return Version.fromVersionAttributes(scope, id, {
+      version: extractVersionFromArn(versionArn),
+      lambda: Function.fromFunctionArn(scope, `${id}Function`, versionArn),
+      versionArn
+    });
+  }
+
   public static fromVersionAttributes(scope: Construct, id: string, attrs: VersionAttributes): IVersion {
     class Import extends Resource implements IVersion {
       public readonly version = attrs.version;
       public readonly lambda = attrs.lambda;
+      public readonly versionArn = attrs.versionArn;
     }
     return new Import(scope, id);
   }
@@ -108,3 +123,20 @@ export class Version extends Resource implements IVersion {
     this.lambda = props.lambda;
   }
 }
+
+/**
+ * Given an opaque (token) ARN, returns a CloudFormation expression that extracts the version
+ * name from the ARN.
+ *
+ * Version ARNs look like this:
+ *
+ *   arn:aws:lambda:region:account-id:function:function-name:version
+ *
+ * ..which means that in order to extract the `version` component from the ARN, we can
+ * split the ARN using ":" and select the component in index 7.
+ *
+ * @returns `FnSelect(7, FnSplit(':', arn))`
+ */
+function extractVersionFromArn(arn: string) {
+  return Fn.select(7, Fn.split(':', arn));
+}