fix(stepfunctions-tasks): EvaluateExpression is limited to expression…

…s that contain state paths (aws#7774) fixes aws#7655
polyakov-v · May 12, 2020 · 97f4f01 · 97f4f01
1 parent cb3c184
commit 97f4f01
Show file tree

Hide file tree

Showing 4 changed files with 77 additions and 23 deletions.
diff --git a/packages/@aws-cdk/aws-stepfunctions-tasks/lib/evaluate-expression.ts b/packages/@aws-cdk/aws-stepfunctions-tasks/lib/evaluate-expression.ts
@@ -11,7 +11,7 @@ import * as path from 'path';
  */
 export interface EvaluateExpressionProps {
   /**
-   * The expression to evaluate. It must contain state paths.
+   * The expression to evaluate. The expression may contain state paths.
    *
    * @example '$.a + $.b'
    */
@@ -56,30 +56,30 @@ export class EvaluateExpression implements sfn.IStepFunctionsTask {
   public bind(task: sfn.Task): sfn.StepFunctionsTaskConfig {
     const matches = this.props.expression.match(/\$[.\[][.a-zA-Z[\]0-9]+/g);
 
-    if (!matches) {
-      throw new Error('No paths found in expression');
+    let expressionAttributeValues = {};
+    if (matches) {
+      expressionAttributeValues = matches.reduce(
+        (acc, m) => ({
+          ...acc,
+          [m]: sfn.Data.stringAt(m), // It's okay to always use `stringAt` here
+        }),
+        {},
+      );
     }
 
-    const expressionAttributeValues = matches.reduce(
-      (acc, m) => ({
-        ...acc,
-        [m]: sfn.Data.stringAt(m), // It's okay to always use `stringAt` here
-      }),
-      {},
-    );
-
     const evalFn = createEvalFn(this.props.runtime || lambda.Runtime.NODEJS_10_X, task);
 
+    const parameters: Event = {
+      expression: this.props.expression,
+      expressionAttributeValues,
+    };
     return {
       resourceArn: evalFn.functionArn,
       policyStatements: [new iam.PolicyStatement({
         resources: [evalFn.functionArn],
         actions: ['lambda:InvokeFunction'],
       })],
-      parameters: {
-        expression: this.props.expression,
-        expressionAttributeValues,
-      } as Event,
+      parameters,
     };
   }
 }

diff --git a/packages/@aws-cdk/aws-stepfunctions-tasks/test/evaluate-expression.test.ts b/packages/@aws-cdk/aws-stepfunctions-tasks/test/evaluate-expression.test.ts
@@ -43,11 +43,32 @@ test('Eval with Node.js', () => {
   });
 });
 
-test('Throws when expression does not contain paths', () => {
+test('expression does not contain paths', () => {
   // WHEN
-  expect(() => new sfn.Task(stack, 'Task', {
+  const task = new sfn.Task(stack, 'Task', {
     task: new tasks.EvaluateExpression({
       expression: '2 + 2',
     }),
-  })).toThrow(/No paths found in expression/);
+  });
+  new sfn.StateMachine(stack, 'SM', {
+    definition: task,
+  });
+
+  expect(stack).toHaveResource('AWS::StepFunctions::StateMachine', {
+    DefinitionString: {
+      'Fn::Join': [
+        '',
+        [
+          '{"StartAt":"Task","States":{"Task":{"End":true,"Parameters":{"expression":"2 + 2",\"expressionAttributeValues\":{}},"Type":"Task","Resource":"',
+          {
+            'Fn::GetAtt': [
+              'Evala0d2ce44871b4e7487a1f5e63d7c3bdc4DAC06E1',
+              'Arn',
+            ],
+          },
+          '"}}}',
+        ],
+      ],
+    },
+  });
 });
diff --git a/packages/@aws-cdk/aws-stepfunctions-tasks/test/integ.evaluate-expression.expected.json b/packages/@aws-cdk/aws-stepfunctions-tasks/test/integ.evaluate-expression.expected.json
@@ -160,7 +160,14 @@
                   "Arn"
                 ]
               },
-              "\",\"ResultPath\":\"$.waitSeconds\"},\"Wait\":{\"Type\":\"Wait\",\"SecondsPath\":\"$.waitSeconds\",\"End\":true}}}"
+              "\",\"ResultPath\":\"$.d\"},\"Wait\":{\"Type\":\"Wait\",\"SecondsPath\":\"$.d\",\"Next\":\"Now\"},\"Now\":{\"End\":true,\"Parameters\":{\"expression\":\"(new Date()).toUTCString()\",\"expressionAttributeValues\":{}},\"Type\":\"Task\",\"Resource\":\"",
+              {
+                "Fn::GetAtt": [
+                  "Evala0d2ce44871b4e7487a1f5e63d7c3bdc4DAC06E1",
+                  "Arn"
+                ]
+              },
+              "\",\"ResultPath\":\"$.now\"}}}"
             ]
           ]
         },
@@ -190,5 +197,12 @@
       "Type": "String",
       "Description": "Artifact hash for asset \"26ff0ffbfcb72e0fa136547addc06082857c59c734b1dd8c4294b58f03f1d26c\""
     }
+  },
+  "Outputs": {
+    "StateMachineARN": {
+      "Value": {
+        "Ref": "StateMachine2E01A3A5"
+      }
+    }
   }
 }
diff --git a/packages/@aws-cdk/aws-stepfunctions-tasks/test/integ.evaluate-expression.ts b/packages/@aws-cdk/aws-stepfunctions-tasks/test/integ.evaluate-expression.ts
@@ -2,6 +2,13 @@ import * as sfn from '@aws-cdk/aws-stepfunctions';
 import * as cdk from '@aws-cdk/core';
 import * as tasks from '../lib';
 
+/*
+ * Stack verification steps:
+ * * aws stepfunctions start-execution --input '{"a": 3, "b": 4}' --state-machine-arn <StateMachineARN>
+ * * aws stepfunctions describe-execution --execution-arn <execution-arn>
+ * * The output here should contain `status: "SUCCEEDED"` and `output: "{ a: 3, b: 4, c: 7, d: 14, now: <current date> }"
+ */
+
 const app = new cdk.App();
 const stack = new cdk.Stack(app, 'aws-stepfunctions-integ');
 
@@ -16,15 +23,27 @@ const multiply = new sfn.Task(stack, 'Multiply', {
   task: new tasks.EvaluateExpression({
     expression: '$.c * 2',
   }),
-  resultPath: '$.waitSeconds',
+  resultPath: '$.d',
 });
 
-new sfn.StateMachine(stack, 'StateMachine', {
+const now = new sfn.Task(stack, 'Now', {
+  task: new tasks.EvaluateExpression({
+    expression: '(new Date()).toUTCString()',
+  }),
+  resultPath: '$.now',
+});
+
+const statemachine = new sfn.StateMachine(stack, 'StateMachine', {
   definition: sum
     .next(multiply)
     .next(new sfn.Wait(stack, 'Wait', {
-      time: sfn.WaitTime.secondsPath('$.waitSeconds'),
-    })),
+      time: sfn.WaitTime.secondsPath('$.d'),
+    }))
+    .next(now),
+});
+
+new cdk.CfnOutput(stack, 'StateMachineARN', {
+  value: statemachine.stateMachineArn,
 });
 
 app.synth();