fix(aws-events): ergonomics improvements to CloudWatch Events (#1570)

Fixes the following things for CloudWatch events:

* Support newlines in CloudWatch Events textTemplate as intended, by making a newline-separated list of JSON strings. Fixes #1514.
*  `jsonTemplate` now accepts arbitrary objects. They will be JSONified automatically. Fixes #1198.
* Explicitly implement `IEventRuleTarget` on stepfunctions StateMachine so that Java/.NET users can trigger StateMachines using CloudWatch Events. Fixes part of #1275.

examples/cdk-examples-typescript/cloudwatch-events/cdk.json

@@ -0,0 +1,3 @@
+{
+  "app": "node index"
+}

examples/cdk-examples-typescript/cloudwatch-events/index.ts

@@ -0,0 +1,25 @@
+import events = require('@aws-cdk/aws-events');
+import sns = require('@aws-cdk/aws-sns');
+import cdk = require('@aws-cdk/cdk');
+
+const app = new cdk.App();
+
+class CloudWatchEventsExample extends cdk.Stack {
+  constructor(scope: cdk.App, id: string) {
+    super(scope, id);
+
+    const topic = new sns.Topic(this, 'TestTopic');
+
+    const event = new events.EventRule(this, 'Rule', {
+      scheduleExpression: 'rate(1 minute)'
+    });
+
+    event.addTarget(topic, {
+      textTemplate: 'one line\nsecond line'
+    });
+  }
+}
+
+new CloudWatchEventsExample(app, 'CWE-Example');
+
+app.run();

examples/cdk-examples-typescript/package.json

@@ -37,6 +37,7 @@
     "@aws-cdk/aws-rds": "^0.22.0",
     "@aws-cdk/aws-s3": "^0.22.0",
     "@aws-cdk/aws-sns": "^0.22.0",
+    "@aws-cdk/aws-events": "^0.22.0",
     "@aws-cdk/aws-sqs": "^0.22.0",
     "@aws-cdk/cdk": "^0.22.0",
     "@aws-cdk/runtime-values": "^0.22.0"

packages/@aws-cdk/aws-events/lib/rule.ts

@@ -116,6 +116,7 @@ export class EventRule extends Construct implements IEventRule {
    */
   public addTarget(target?: IEventRuleTarget, inputOptions?: TargetInputTemplate) {
     if (!target) { return; }
+    const self = this;
 
     const targetProps = target.asEventRuleTarget(this.ruleArn, this.node.uniqueId);
 
@@ -145,11 +146,15 @@ export class EventRule extends Construct implements IEventRule {
       let inputTemplate: any;
 
       if (inputOptions.jsonTemplate) {
-        inputTemplate = inputOptions.jsonTemplate;
-      } else if (typeof(inputOptions.textTemplate) === 'string') {
-        inputTemplate = JSON.stringify(inputOptions.textTemplate);
+        inputTemplate = typeof inputOptions.jsonTemplate === 'string'
+            ? inputOptions.jsonTemplate
+            : self.node.stringifyJson(inputOptions.jsonTemplate);
       } else {
-        inputTemplate = `"${inputOptions.textTemplate}"`;
+        inputTemplate = typeof(inputOptions.textTemplate) === 'string'
+            // Newline separated list of JSON-encoded strings
+            ? inputOptions.textTemplate.split('\n').map(x => self.node.stringifyJson(x)).join('\n')
+            // Some object, stringify it, then stringify the string for proper escaping
+            : self.node.stringifyJson(self.node.stringifyJson(inputOptions.textTemplate));
       }
 
       return {

packages/@aws-cdk/aws-events/test/test.rule.ts

@@ -1,4 +1,4 @@
-import { expect, haveResource } from '@aws-cdk/assert';
+import { expect, haveResource, haveResourceLike } from '@aws-cdk/assert';
 import cdk = require('@aws-cdk/cdk');
 import { Stack } from '@aws-cdk/cdk';
 import { Test } from 'nodeunit';
@@ -351,5 +351,122 @@ export = {
     test.deepEqual(importedRule.ruleArn, 'arn:of:rule');
 
     test.done();
-  }
+  },
+
+  'json template': {
+    'can just be a JSON object'(test: Test) {
+      // GIVEN
+      const stack = new Stack();
+      const rule = new EventRule(stack, 'Rule', {
+        scheduleExpression: 'rate(1 minute)'
+      });
+
+      // WHEN
+      rule.addTarget(new SomeTarget(), {
+        jsonTemplate: { SomeObject: 'withAValue' },
+      });
+
+      // THEN
+      expect(stack).to(haveResourceLike('AWS::Events::Rule', {
+        Targets: [
+          {
+            InputTransformer: {
+              InputTemplate: "{\"SomeObject\":\"withAValue\"}"
+            },
+          }
+        ]
+      }));
+      test.done();
+    },
+  },
+
+  'text templates': {
+    'strings with newlines are serialized to a newline-delimited list of JSON strings'(test: Test) {
+      // GIVEN
+      const stack = new Stack();
+      const rule = new EventRule(stack, 'Rule', {
+        scheduleExpression: 'rate(1 minute)'
+      });
+
+      // WHEN
+      rule.addTarget(new SomeTarget(), {
+        textTemplate: 'I have\nmultiple lines',
+      });
+
+      // THEN
+      expect(stack).to(haveResourceLike('AWS::Events::Rule', {
+        Targets: [
+          {
+            InputTransformer: {
+              InputTemplate: "\"I have\"\n\"multiple lines\""
+            },
+          }
+        ]
+      }));
+
+      test.done();
+    },
+
+    'escaped newlines are not interpreted as newlines'(test: Test) {
+      // GIVEN
+      const stack = new Stack();
+      const rule = new EventRule(stack, 'Rule', {
+        scheduleExpression: 'rate(1 minute)'
+      });
+
+      // WHEN
+      rule.addTarget(new SomeTarget(), {
+        textTemplate: 'this is not\\na real newline',
+      });
+
+      // THEN
+      expect(stack).to(haveResourceLike('AWS::Events::Rule', {
+        Targets: [
+          {
+            InputTransformer: {
+              InputTemplate: "\"this is not\\\\na real newline\""
+            },
+          }
+        ]
+      }));
+
+      test.done();
+    },
+
+    'can use Tokens in text templates'(test: Test) {
+      // GIVEN
+      const stack = new Stack();
+      const rule = new EventRule(stack, 'Rule', {
+        scheduleExpression: 'rate(1 minute)'
+      });
+
+      const world = new cdk.Token(() => 'world');
+
+      // WHEN
+      rule.addTarget(new SomeTarget(), {
+        textTemplate: `hello ${world}`,
+      });
+
+      // THEN
+      expect(stack).to(haveResourceLike('AWS::Events::Rule', {
+        Targets: [
+          {
+            InputTransformer: {
+              InputTemplate: "\"hello world\""
+            },
+          }
+        ]
+      }));
+
+      test.done();
+    }
+  },
 };
+
+class SomeTarget implements IEventRuleTarget {
+  public asEventRuleTarget() {
+    return {
+      id: 'T1', arn: 'ARN1', kinesisParameters: { partitionKeyPath: 'partitionKeyPath' }
+    };
+  }
+}

packages/@aws-cdk/aws-stepfunctions/lib/state-machine.ts

@@ -40,7 +40,7 @@ export interface StateMachineProps {
 /**
  * Define a StepFunctions State Machine
  */
-export class StateMachine extends cdk.Construct implements IStateMachine {
+export class StateMachine extends cdk.Construct implements IStateMachine, events.IEventRuleTarget {
     /**
      * Import a state machine
      */

packages/@aws-cdk/aws-stepfunctions/test/test.state-machine-resources.ts

@@ -1,4 +1,5 @@
-import { expect, haveResource } from '@aws-cdk/assert';
+import { expect, haveResource, haveResourceLike } from '@aws-cdk/assert';
+import events = require('@aws-cdk/aws-events');
 import iam = require('@aws-cdk/aws-iam');
 import cdk = require('@aws-cdk/cdk');
 import { Test } from 'nodeunit';
@@ -134,7 +135,36 @@ export = {
         });
 
         test.done();
-    }
+    },
+
+    'State machine can be used as Event Rule target'(test: Test) {
+        // GIVEN
+        const stack = new cdk.Stack();
+        const rule = new events.EventRule(stack, 'Rule', {
+                scheduleExpression: 'rate(1 minute)'
+        });
+        const stateMachine = new stepfunctions.StateMachine(stack, 'SM', {
+                definition: new stepfunctions.Wait(stack, 'Hello', {  })
+            });
+
+        // WHEN
+        rule.addTarget(stateMachine, {
+            jsonTemplate: { SomeParam: 'SomeValue' },
+        });
+
+        // THEN
+        expect(stack).to(haveResourceLike('AWS::Events::Rule', {
+            Targets: [
+                {
+                    InputTransformer: {
+                        InputTemplate: "{\"SomeParam\":\"SomeValue\"}"
+                    },
+                }
+            ]
+        }));
+
+        test.done();
+    },
 };
 
 class FakeResource implements stepfunctions.IStepFunctionsTaskResource {