fix(stepfunctions): improve Task payload encoding

packages/@aws-cdk/aws-stepfunctions-tasks/lib/publish-to-topic.ts

@@ -8,17 +8,8 @@ import sfn = require('@aws-cdk/aws-stepfunctions');
 export interface PublishToTopicProps {
   /**
    * The text message to send to the topic.
-   *
-   * @default - Exactly one of `message` and `messageObject` is required.
-   */
-  readonly message?: string;
-
-  /**
-   * Object to be JSON-encoded and used as message
-   *
-   * @default - Exactly one of `message` and `messageObject` is required.
    */
-  readonly messageObject?: {[key: string]: any};
+  readonly message: sfn.TaskInput;
 
   /**
    * If true, send a different message to every subscription type
@@ -46,9 +37,6 @@ export interface PublishToTopicProps {
  */
 export class PublishToTopic implements sfn.IStepFunctionsTask {
   constructor(private readonly topic: sns.ITopic, private readonly props: PublishToTopicProps) {
-    if ((props.message === undefined) === (props.messageObject === undefined)) {
-      throw new Error(`Supply exactly one of 'message' or 'messageObject'`);
-    }
   }
 
   public bind(_task: sfn.Task): sfn.StepFunctionsTaskProperties {
@@ -61,7 +49,7 @@ export class PublishToTopic implements sfn.IStepFunctionsTask {
       parameters: {
         TopicArn: this.topic.topicArn,
         ...sfn.FieldUtils.renderObject({
-          Message: this.props.message || this.props.messageObject,
+          Message: this.props.message.value,
           MessageStructure: this.props.messagePerSubscriptionType ? "json" : undefined,
           Subject: this.props.subject,
         })

packages/@aws-cdk/aws-stepfunctions-tasks/lib/send-to-queue.ts

@@ -7,18 +7,9 @@ import sfn = require('@aws-cdk/aws-stepfunctions');
  */
 export interface SendToQueueProps {
   /**
-   * The text message to send to the topic.
-   *
-   * @default - Exactly one of `message` and `messageObject` is required.
-   */
-  readonly message?: string;
-
-  /**
-   * Object to be JSON-encoded and used as message
-   *
-   * @default - Exactly one of `message` and `messageObject` is required.
+   * The text message to send to the queue.
    */
-  readonly messageObject?: {[key: string]: any};
+  readonly messageBody: sfn.TaskInput;
 
   /**
    * The length of time, in seconds, for which to delay a specific message.
@@ -55,9 +46,6 @@ export interface SendToQueueProps {
  */
 export class SendToQueue implements sfn.IStepFunctionsTask {
   constructor(private readonly queue: sqs.IQueue, private readonly props: SendToQueueProps) {
-    if ((props.message === undefined) === (props.messageObject === undefined)) {
-      throw new Error(`Supply exactly one of 'message' or 'messageObject'`);
-    }
   }
 
   public bind(_task: sfn.Task): sfn.StepFunctionsTaskProperties {
@@ -70,7 +58,7 @@ export class SendToQueue implements sfn.IStepFunctionsTask {
       parameters: {
         QueueUrl: this.queue.queueUrl,
         ...sfn.FieldUtils.renderObject({
-          MessageBody: this.props.message || this.props.messageObject,
+          MessageBody: this.props.messageBody.value,
           DelaySeconds: this.props.delaySeconds,
           MessageDeduplicationId: this.props.messageDeduplicationId,
           MessageGroupId: this.props.messageGroupId,

packages/@aws-cdk/aws-stepfunctions-tasks/test/ecs-tasks.test.ts

@@ -63,7 +63,7 @@ test('Running a Fargate Task', () => {
       {
         containerName: 'TheContainer',
         environment: [
-          {name: 'SOME_KEY', value: sfn.DataField.fromStringAt('$.SomeKey')}
+          {name: 'SOME_KEY', value: sfn.Data.stringAt('$.SomeKey')}
         ]
       }
     ]
@@ -161,7 +161,7 @@ test('Running an EC2 Task with bridge network', () => {
       {
         containerName: 'TheContainer',
         environment: [
-          {name: 'SOME_KEY', value: sfn.DataField.fromStringAt('$.SomeKey')}
+          {name: 'SOME_KEY', value: sfn.Data.stringAt('$.SomeKey')}
         ]
       }
     ]
@@ -295,9 +295,9 @@ test('Running an EC2 Task with overridden number values', () => {
     containerOverrides: [
       {
         containerName: 'TheContainer',
-        command: sfn.DataField.fromListAt('$.TheCommand'),
+        command: sfn.Data.listAt('$.TheCommand'),
         cpu: 5,
-        memoryLimit: sfn.DataField.fromNumberAt('$.MemoryLimit'),
+        memoryLimit: sfn.Data.numberAt('$.MemoryLimit'),
       }
     ]
   });

packages/@aws-cdk/aws-stepfunctions-tasks/test/integ.ec2-task.ts

@@ -37,7 +37,7 @@ const definition = new sfn.Pass(stack, 'Start', {
       environment: [
         {
           name: 'SOME_KEY',
-          value: sfn.DataField.fromStringAt('$.SomeKey')
+          value: sfn.Data.stringAt('$.SomeKey')
         }
       ]
     }

packages/@aws-cdk/aws-stepfunctions-tasks/test/integ.fargate-task.ts

@@ -37,7 +37,7 @@ const definition = new sfn.Pass(stack, 'Start', {
       environment: [
         {
           name: 'SOME_KEY',
-          value: sfn.DataField.fromStringAt('$.SomeKey')
+          value: sfn.Data.stringAt('$.SomeKey')
         }
       ]
     }

packages/@aws-cdk/aws-stepfunctions-tasks/test/publish-to-topic.test.ts

@@ -10,7 +10,7 @@ test('publish to SNS', () => {
 
   // WHEN
   const pub = new sfn.Task(stack, 'Publish', { task: new tasks.PublishToTopic(topic, {
-    message: 'Send this message'
+    message: sfn.TaskInput.fromText('Send this message')
   }) });
 
   // THEN
@@ -32,9 +32,9 @@ test('publish JSON to SNS', () => {
 
   // WHEN
   const pub = new sfn.Task(stack, 'Publish', { task: new tasks.PublishToTopic(topic, {
-    messageObject: {
+    message: sfn.TaskInput.fromObject({
       Input: 'Send this message'
-    }
+    })
   }) });
 
   // THEN

packages/@aws-cdk/aws-stepfunctions-tasks/test/send-to-queue.test.ts

@@ -15,8 +15,8 @@ beforeEach(() => {
 test('publish to queue', () => {
   // WHEN
   const pub = new sfn.Task(stack, 'Send', { task: new tasks.SendToQueue(queue, {
-    message: 'Send this message',
-    messageDeduplicationId: sfn.DataField.fromStringAt('$.deduping'),
+    messageBody: sfn.TaskInput.fromText('Send this message'),
+    messageDeduplicationId: sfn.Data.stringAt('$.deduping'),
   }) });
 
   // THEN
@@ -36,7 +36,7 @@ test('message body can come from state', () => {
   // WHEN
   const pub = new sfn.Task(stack, 'Send', {
     task: new tasks.SendToQueue(queue, {
-      message: sfn.DataField.fromStringAt('$.theMessage')
+      messageBody: sfn.TaskInput.fromDataAt('$.theMessage')
     })
   });
 
@@ -56,10 +56,10 @@ test('message body can be an object', () => {
   // WHEN
   const pub = new sfn.Task(stack, 'Send', {
     task: new tasks.SendToQueue(queue, {
-      messageObject: {
+      messageBody: sfn.TaskInput.fromObject({
         literal: 'literal',
-        SomeInput: sfn.DataField.fromStringAt('$.theMessage')
-      }
+        SomeInput: sfn.Data.stringAt('$.theMessage')
+      })
     })
   });
 
@@ -82,9 +82,9 @@ test('message body object can contain references', () => {
   // WHEN
   const pub = new sfn.Task(stack, 'Send', {
     task: new tasks.SendToQueue(queue, {
-      messageObject: {
+      messageBody: sfn.TaskInput.fromObject({
         queueArn: queue.queueArn
-      }
+      })
     })
   });
 

packages/@aws-cdk/aws-stepfunctions/README.md

@@ -119,8 +119,8 @@ couple of the tasks available are:
 
 Many tasks take parameters. The values for those can either be supplied
 directly in the workflow definition (by specifying their values), or at
-runtime by passing a value obtained from the static functions on `DataField`,
-such as `DataField.fromStringAt()`.
+runtime by passing a value obtained from the static functions on `Data`,
+such as `Data.stringAt()`.
 
 If so, the value is taken from the indicated location in the state JSON,
 similar to (for example) `inputPath`.
@@ -155,9 +155,22 @@ import sns = require('@aws-cdk/aws-sns');
 // ...
 
 const topic = new sns.Topic(this, 'Topic');
-const task = new sfn.Task(this, 'Publish', {
+
+// Use a field from the execution data as message.
+const task1 = new sfn.Task(this, 'Publish1', {
+    task: new tasks.PublishToTopic(topic, {
+        message: TaskInput.fromDataAt('$.state.message'),
+    })
+});
+
+// Combine a field from the execution data with
+// a literal object.
+const task2 = new sfn.Task(this, 'Publish2', {
     task: new tasks.PublishToTopic(topic, {
-        message: DataField.fromStringAt('$.state.message'),
+        message: TaskInput.fromObject({
+            field1: 'somedata',
+            field2: Data.stringAt('$.field2'),
+        })
     })
 });
 ```
@@ -170,11 +183,26 @@ import sqs = require('@aws-cdk/aws-sqs');
 // ...
 
 const queue = new sns.Queue(this, 'Queue');
-const task = new sfn.Task(this, 'Send', {
+
+// Use a field from the execution data as message.
+const task1 = new sfn.Task(this, 'Send1', {
+    task: new tasks.SendToQueue(queue, {
+        messageBody: TaskInput.fromDataAt('$.message'),
+        // Only for FIFO queues
+        messageGroupId: '1234'
+    })
+});
+
+// Combine a field from the execution data with
+// a literal object.
+const task2 = new sfn.Task(this, 'Send2', {
     task: new tasks.SendToQueue(queue, {
-        messageBody: DataField.fromStringAt('$.message'),
+        messageBody: TaskInput.fromObject({
+            field1: 'somedata',
+            field2: Data.stringAt('$.field2'),
+        }),
         // Only for FIFO queues
-        messageGroupId: DataField.fromStringAt('$.messageGroupId'),
+        messageGroupId: '1234'
     })
 });
 ```
@@ -195,7 +223,7 @@ const fargateTask = new ecs.RunEcsFargateTask({
       environment: [
         {
           name: 'CONTAINER_INPUT',
-          value: DataField.fromStringAt('$.valueFromStateData')
+          value: Data.stringAt('$.valueFromStateData')
         }
       ]
     }
@@ -464,4 +492,4 @@ Contributions welcome:
 - [ ] A single `LambdaTask` class that is both a `Lambda` and a `Task` in one
   might make for a nice API.
 - [ ] Expression parser for Conditions.
-- [ ] Simulate state machines in unit tests.
+- [ ] Simulate state machines in unit tests.

packages/@aws-cdk/aws-stepfunctions/lib/fields.ts

@@ -3,27 +3,27 @@ import { findReferencedPaths, JsonPathToken, renderObject } from "./json-path";
 /**
  * Extract a field from the State Machine data that gets passed around between states
  */
-export class DataField {
+export class Data {
   /**
    * Instead of using a literal string, get the value from a JSON path
    */
-  public static fromStringAt(path: string): string {
+  public static stringAt(path: string): string {
     validateDataPath(path);
     return new JsonPathToken(path).toString();
   }
 
   /**
    * Instead of using a literal string list, get the value from a JSON path
    */
-  public static fromListAt(path: string): string[] {
+  public static listAt(path: string): string[] {
     validateDataPath(path);
     return new JsonPathToken(path).toList();
   }
 
   /**
    * Instead of using a literal number, get the value from a JSON path
    */
-  public static fromNumberAt(path: string): number {
+  public static numberAt(path: string): number {
     validateDataPath(path);
     return new JsonPathToken(path).toNumber();
   }
@@ -47,19 +47,19 @@ export class DataField {
  *
  * @see https://docs.aws.amazon.com/step-functions/latest/dg/connect-to-resource.html#wait-token-contextobject
  */
-export class ContextField {
+export class Context {
   /**
    * Instead of using a literal string, get the value from a JSON path
    */
-  public static fromStringAt(path: string): string {
+  public static stringAt(path: string): string {
     validateContextPath(path);
     return new JsonPathToken(path).toString();
   }
 
   /**
    * Instead of using a literal number, get the value from a JSON path
    */
-  public static fromNumberAt(path: string): number {
+  public static numberAt(path: string): number {
     validateContextPath(path);
     return new JsonPathToken(path).toNumber();
   }
@@ -89,7 +89,7 @@ export class ContextField {
   }
 }
 
-/**gg
+/**
  * Helper functions to work with structures containing fields
  */
 export class FieldUtils {
@@ -125,12 +125,12 @@ export class FieldUtils {
 
 function validateDataPath(path: string) {
   if (!path.startsWith('$.')) {
-    throw new Error("DataField JSON path values must start with '$.'");
+    throw new Error("Data JSON path values must start with '$.'");
   }
 }
 
 function validateContextPath(path: string) {
   if (!path.startsWith('$$.')) {
-    throw new Error("ContextField JSON path values must start with '$$.'");
+    throw new Error("Context JSON path values must start with '$$.'");
   }
 }

packages/@aws-cdk/aws-stepfunctions/lib/index.ts

@@ -1,5 +1,6 @@
 export * from './fields';
 export * from './activity';
+export * from './input';
 export * from './types';
 export * from './condition';
 export * from './state-machine';