fix(stepfunctions): cannot use intrinsic functions in Fail state

[sakurai-ryo]

Issue # (if applicable)

Closes #30063

Reason for this change

In the Fail state, we can specify intrinsic functions and json paths as the CausePath and ErrorPath properties.
Currently, however, specifying intrinsic functions as a string will result in an error.
https://docs.aws.amazon.com/step-functions/latest/dg/amazon-states-language-fail-state.html

export class SampleStack extends cdk.Stack {
  constructor(scope: Construct, id: string, props?: cdk.StackProps) {
    super(scope, id, props);

    const fail = new stepfunctions.Fail(this, "Fail", {
      errorPath: "$.error", // OK
      causePath: "States.Format('cause: {}', $.cause)", // Error
    });

    const sm = new stepfunctions.StateMachine(this, "StateMachine", {
      definitionBody: stepfunctions.DefinitionBody.fromChainable(fail),
      timeout: cdk.Duration.minutes(5)
    });
  }
}

Error: Expected JSON path to start with '$', got: States.Format('cause: {}', $.cause)

Description of changes

The value passed to the renderJsonPath function is expected to be a string starting with $ if it is not a token.
However, if you pass intrinsic functions as strings to the CausePath and ErrorPath properties, they will never start with $.
Therefore, I fixed not to call the renderJsonPath function if the intrinsic functions are specified as strings.

Another change was the addition of validation since error and errorPath, cause and causePath cannot be specified simultaneously.

Description of how you validated changes

I added unit tests to verify that passing intrinsic functions as strings do not cause an error.

Tests were also added to verify that errors occur when errors and paths are specified at the same time and when cause and cause paths are specified at the same time.
https://docs.aws.amazon.com/step-functions/latest/dg/amazon-states-language-fail-state.html#:~:text=%2C%20and%20States.UUID.-,Important,-You%20can%20specify%20either%20Cause
https://docs.aws.amazon.com/step-functions/latest/dg/amazon-states-language-fail-state.html#:~:text=%2C%20and%20States.UUID.-,Important,-You%20can%20specify%20either%20Error

Checklist

• My code adheres to the CONTRIBUTING GUIDE and DESIGN GUIDELINES

---

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache-2.0 license

[aws-cdk-automation]

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[sakurai-ryo]

Exemption Request
I think that unit tests cover the scope of this change.

[gracelu0]

Hi @sakurai-ryo , thank you for working on this! The added validation is great. I left one comment about adding an unhappy path test case if you could address that, otherwise lgtm!

[gracelu0]

Should we check for the supported intrinsic functions here? Currently passing in any string that doesn't start with '$' would still pass, correct? I'd like to see a test case where the value is a plain string (neither an intrinsic function nor Json path) to understand the expected behaviour.

[sakurai-ryo]

Yes, correct.
I added the validation along with the test because validation is possible for strings.
However, the validation checks only the start of the string.
This is because a parser is needed if we also want to check the syntax of intrinsics.

[sakurai-ryo]

Thanks for your review @gracelu0 !
I added validations and tests to verify.

[aws-cdk-automation]

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• CodeBuild project: AutoBuildv2Project1C6BFA3F-wQm2hXv2jqQv
• Commit ID: 60c1bba
• Result: SUCCEEDED
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[gracelu0]

Thanks for addressing the feedback promptly! We appreciate your contribution :)

✅ Updated pull request passes all PRLinter validations. Dismissing previous PRLinter review.

[mergify]

Thank you for contributing! Your pull request will be updated from main and then merged automatically (do not update manually, and be sure to allow changes to be pushed to your fork).

[kimyx]

Thanks for your work on this, @sakurai-ryo! Looking forward to giving it a try on my application.

[kimyx]

I tried removing my workaround and deploying with cdk version 2.144.0 (build 5fb15bc) and see the same error as before.

RuntimeError: Expected JSON path to start with '$', got: States.Format('l1a-step-function FAILED: {}',$.Cause.StatusReason)

From what I can see of the build pipeline, 2.144.0 should have the relevant changes. Do you agree? If so, I'll dig deeper.

[kimyx]

in case this is helpful:

  Error: Expected JSON path to start with '$', got: States.Format('l1a-step-function FAILED: {}',$.Cause.StatusReason)
      at renderJsonPath (/var/folders/_b/2b2x6djs2q77mc8d8pt49r0m007nfk/T/jsii-kernel-2dUphk/node_modules/aws-cdk-lib/aws-stepfunctions/lib/states/state.js:1:9755)
      at Fail.toStateJson (/var/folders/_b/2b2x6djs2q77mc8d8pt49r0m007nfk/T/jsii-kernel-2dUphk/node_modules/aws-cdk-lib/aws-stepfunctions/lib/states/fail.js:1:978)
      at StateGraph.toGraphJson (/var/folders/_b/2b2x6djs2q77mc8d8pt49r0m007nfk/T/jsii-kernel-2dUphk/node_modules/aws-cdk-lib/aws-stepfunctions/lib/state-graph.js:1:2159)
      at ChainDefinitionBody.bind (/var/folders/_b/2b2x6djs2q77mc8d8pt49r0m007nfk/T/jsii-kernel-2dUphk/node_modules/aws-cdk-lib/aws-stepfunctions/lib/state-machine.js:1:12008)
      at new StateMachine (/var/folders/_b/2b2x6djs2q77mc8d8pt49r0m007nfk/T/jsii-kernel-2dUphk/node_modules/aws-cdk-lib/aws-stepfunctions/lib/state-machine.js:1:6368)
      at Kernel._Kernel_create (/private/var/folders/_b/2b2x6djs2q77mc8d8pt49r0m007nfk/T/tmp0zm93wtb/lib/program.js:10108:25)
      at Kernel.create (/private/var/folders/_b/2b2x6djs2q77mc8d8pt49r0m007nfk/T/tmp0zm93wtb/lib/program.js:9779:93)
      at KernelHost.processRequest (/private/var/folders/_b/2b2x6djs2q77mc8d8pt49r0m007nfk/T/tmp0zm93wtb/lib/program.js:11696:36)
      at KernelHost.run (/private/var/folders/_b/2b2x6djs2q77mc8d8pt49r0m007nfk/T/tmp0zm93wtb/lib/program.js:11656:22)
      at Immediate._onImmediate (/private/var/folders/_b/2b2x6djs2q77mc8d8pt49r0m007nfk/T/tmp0zm93wtb/lib/program.js:11657:46)

[sakurai-ryo]

Thanks @kimyx.
I was able to deploy the following code correctly on my laptop with v2.144.0 using TypeScript.

import * as cdk from 'aws-cdk-lib';
import { Construct } from 'constructs';
import * as sfn from 'aws-cdk-lib/aws-stepfunctions';

export class StepFnStack extends cdk.Stack {
  constructor(scope: Construct, id: string, props?: cdk.StackProps) {
    super(scope, id, props);

    const fail = new sfn.Fail(this, 'Fail', {
        errorPath: "States.Format('l1a-step-function FAILED: {}',$.Cause.StatusReason)",
        causePath: "States.Format('Hello, my name is {}.', $.name)",
    });

    new sfn.StateMachine(this, 'StateMachine', {
        definitionBody: sfn.DefinitionBody.fromChainable(fail),
    });
  }
}

{
  "name": "cdk-test",
  "version": "0.1.0",
  "bin": {
    "kms-import": "bin/cdk-test.js"
  },
  "scripts": {
    "build": "tsc",
    "watch": "tsc -w",
    "test": "jest",
    "cdk": "cdk"
  },
  "devDependencies": {
    "@types/jest": "^29.5.12",
    "@types/node": "20.12.7",
    "jest": "^29.7.0",
    "ts-jest": "^29.1.2",
    "aws-cdk": "2.143.0",
    "ts-node": "^10.9.2",
    "typescript": "~5.4.5"
  },
  "dependencies": {
    "aws-cdk-lib": "2.144.0",
    "constructs": "^10.0.0",
    "source-map-support": "^0.5.21"
  }
}

Cloud you please show me with the entire code that can reproduce this error?