feat(cloudfront): define lambda@edge as resolvable resource (#2861)

* feat(cloudfront): define lambda@edge as resolvable resource

This declaration is required for deploying custom resources as lamdba
association, which by itself is required to deploy a lambda@edge for a
stack which is in a different region as 'us-east-1'.

Relates to #1575

* test: simplified test case by just test resources required for the case

* 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.

* refactor: resolve conflicts

* refactor: update based on review

* refactor: use version arn as function arn

* Fixing package.json

* Fix tests

Author: KnisterPeter

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

@@ -90,4 +90,4 @@
     "node": ">= 8.10.0"
   },
   "stability": "experimental"
-}
+}

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

@@ -1,8 +1,9 @@
-import { expect } from '@aws-cdk/assert';
+import { expect, haveResourceLike } from '@aws-cdk/assert';
+import * as lambda from '@aws-cdk/aws-lambda';
 import s3 = require('@aws-cdk/aws-s3');
 import cdk = require('@aws-cdk/core');
 import { Test } from 'nodeunit';
-import { CloudFrontWebDistribution, ViewerProtocolPolicy } from '../lib';
+import { CloudFrontWebDistribution, LambdaEdgeEventType, ViewerProtocolPolicy } from '../lib';
 
 // tslint:disable:object-literal-key-quotes
 
@@ -321,4 +322,58 @@ export = {
     test.done();
   },
 
+  'distribution with resolvable lambda-association'(test: Test) {
+    const stack = new cdk.Stack();
+    const sourceBucket = new s3.Bucket(stack, 'Bucket');
+
+    const lambdaFunction = new lambda.SingletonFunction(stack, 'Lambda', {
+      uuid: 'xxxx-xxxx-xxxx-xxxx',
+      code: lambda.Code.inline('foo'),
+      handler: 'index.handler',
+      runtime: lambda.Runtime.NODEJS_8_10
+    });
+
+    new CloudFrontWebDistribution(stack, 'AnAmazingWebsiteProbably', {
+      originConfigs: [
+        {
+          s3OriginSource: {
+            s3BucketSource: sourceBucket
+          },
+          behaviors: [
+            {
+              isDefaultBehavior: true,
+              lambdaFunctionAssociations: [{
+                eventType: LambdaEdgeEventType.ORIGIN_REQUEST,
+                lambdaFunction: lambdaFunction.latestVersion
+              }]
+            }
+          ]
+        }
+      ]
+    });
+
+    expect(stack).to(haveResourceLike('AWS::CloudFront::Distribution', {
+      "DistributionConfig": {
+        "DefaultCacheBehavior": {
+          "LambdaFunctionAssociations": [
+            {
+              "EventType": "origin-request",
+              "LambdaFunctionARN": {
+                "Fn::Join": [
+                  "",
+                  [
+                    { "Fn::GetAtt": [ "SingletonLambdaxxxxxxxxxxxxxxxx69D4268A", "Arn" ] },
+                    ":$LATEST"
+                  ]
+                ]
+              }
+            }
+          ],
+        },
+      }
+    }));
+
+    test.done();
+  },
+
 };

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

@@ -1,5 +1,6 @@
 import cloudwatch = require('@aws-cdk/aws-cloudwatch');
-import { Construct } from '@aws-cdk/core';
+import { Construct, Fn } from '@aws-cdk/core';
+import { Function } from './function';
 import { IFunction, QualifiedFunctionBase } from './function-base';
 import { CfnVersion } from './lambda.generated';
 
@@ -72,6 +73,30 @@ export interface VersionAttributes {
  */
 export class Version extends QualifiedFunctionBase implements IVersion {
 
+  /**
+   * Construct a Version object from a Version ARN.
+   *
+   * @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 {
+    const version = extractVersionFromArn(versionArn);
+    const lambda = Function.fromFunctionArn(scope, `${id}Function`, versionArn);
+
+    class Import extends QualifiedFunctionBase implements IVersion {
+      public readonly version = version;
+      public readonly lambda = lambda;
+      public readonly functionName = `${lambda.functionName}:${version}`;
+      public readonly functionArn = versionArn;
+      public readonly grantPrincipal = lambda.grantPrincipal;
+      public readonly role = lambda.role;
+
+      protected readonly canCreatePermissions = false;
+    }
+    return new Import(scope, id);
+  }
+
   public static fromVersionAttributes(scope: Construct, id: string, attrs: VersionAttributes): IVersion {
     class Import extends QualifiedFunctionBase implements IVersion {
       public readonly version = attrs.version;
@@ -131,3 +156,20 @@ export class Version extends QualifiedFunctionBase implements IVersion {
     });
   }
 }
+
+/**
+ * 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));
+}

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

@@ -0,0 +1,33 @@
+import { expect } from '@aws-cdk/assert';
+import cdk = require('@aws-cdk/core');
+import { Test } from 'nodeunit';
+import lambda = require('../lib');
+
+// tslint:disable:object-literal-key-quotes
+
+export = {
+  'can import a Lambda version by ARN'(test: Test) {
+    // GIVEN
+    const stack = new cdk.Stack();
+
+    // WHEN
+    const version = lambda.Version.fromVersionArn(stack, 'Version', 'arn:aws:lambda:region:account-id:function:function-name:version');
+
+    new cdk.CfnOutput(stack, 'ARN', { value: version.functionArn });
+    new cdk.CfnOutput(stack, 'Name', { value: version.functionName });
+
+    // THEN
+    expect(stack).toMatch({
+      Outputs: {
+        ARN: {
+          Value: "arn:aws:lambda:region:account-id:function:function-name:version"
+        },
+        Name: {
+          Value: "function-name:version"
+        }
+      }
+    });
+
+    test.done();
+  },
+};