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step function: Fail state cause_path generates error using States.Format #30063

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@aws-cdk/aws-lambda Related to AWS Lambda bug This issue is a bug. effort/small Small work item – less than a day of effort p1

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@kimyx
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kimyx commented May 5, 2024

Describe the bug

The AWS documentation for Fail state says that the CausePath argument accepts the use of intrinsic functions as well as reference paths. The CDK support for the Fail state works with reference paths but not with intrinsic functions, particularly States.Format(). It generates this error:

RuntimeError: Expected JSON path to start with '$', got: States.Format('LogStreamName: {}', $.Cause.Container.LogStreamName)

Expected Behavior

I expected to be able to use States.Format when building a Fail state.

Current Behavior

$ cdk deploy  --exclusively JobPollerStack
...
jsii.errors.JavaScriptError:
  Error: Expected JSON path to start with '$', got: States.Format('LogStreamName: {}', $.Cause.Container.LogStreamName)
      at renderJsonPath (/var/folders/_b/2b2x6djs2q77mc8d8pt49r0m007nfk/T/jsii-kernel-3Ir8Er/node_modules/aws-cdk-lib/aws-stepfunctions/lib/states/state.js:1:9755)
      at Fail.toStateJson (/var/folders/_b/2b2x6djs2q77mc8d8pt49r0m007nfk/T/jsii-kernel-3Ir8Er/node_modules/aws-cdk-lib/aws-stepfunctions/lib/states/fail.js:1:1050)
      at StateGraph.toGraphJson (/var/folders/_b/2b2x6djs2q77mc8d8pt49r0m007nfk/T/jsii-kernel-3Ir8Er/node_modules/aws-cdk-lib/aws-stepfunctions/lib/state-graph.js:1:2159)
      at ChainDefinitionBody.bind (/var/folders/_b/2b2x6djs2q77mc8d8pt49r0m007nfk/T/jsii-kernel-3Ir8Er/node_modules/aws-cdk-lib/aws-stepfunctions/lib/state-machine.js:1:12008)
      at new StateMachine (/var/folders/_b/2b2x6djs2q77mc8d8pt49r0m007nfk/T/jsii-kernel-3Ir8Er/node_modules/aws-cdk-lib/aws-stepfunctions/lib/state-machine.js:1:6368)
      at Kernel._Kernel_create (/private/var/folders/_b/2b2x6djs2q77mc8d8pt49r0m007nfk/T/tmpv90l1_x_/lib/program.js:10108:25)
      at Kernel.create (/private/var/folders/_b/2b2x6djs2q77mc8d8pt49r0m007nfk/T/tmpv90l1_x_/lib/program.js:9779:93)
      at KernelHost.processRequest (/private/var/folders/_b/2b2x6djs2q77mc8d8pt49r0m007nfk/T/tmpv90l1_x_/lib/program.js:11696:36)
      at KernelHost.run (/private/var/folders/_b/2b2x6djs2q77mc8d8pt49r0m007nfk/T/tmpv90l1_x_/lib/program.js:11656:22)
      at Immediate._onImmediate (/private/var/folders/_b/2b2x6djs2q77mc8d8pt49r0m007nfk/T/tmpv90l1_x_/lib/program.js:11657:46)

The above exception was the direct cause of the following exception:

Traceback (most recent call last):
  File "/Users/kiko1739/code/csds/src/csds_app.py", line 682, in <module>
    job_poller_stack = JobPollerStack(app, 'BadStack')
                       ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/Users/kiko1739/code/csds/venv_311/lib/python3.11/site-packages/jsii/_runtime.py", line 118, in __call__
    inst = super(JSIIMeta, cast(JSIIMeta, cls)).__call__(*args, **kwargs)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/Users/kiko1739/code/csds/src/stacks/step_bad_stack.py", line 85, in __init__
    sm = _aws_stepfunctions.StateMachine(
         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/Users/kiko1739/code/csds/venv_311/lib/python3.11/site-packages/jsii/_runtime.py", line 118, in __call__
    inst = super(JSIIMeta, cast(JSIIMeta, cls)).__call__(*args, **kwargs)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/Users/kiko1739/code/csds/venv_311/lib/python3.11/site-packages/aws_cdk/aws_stepfunctions/__init__.py", line 10097, in __init__
    jsii.create(self.__class__, self, [scope, id, props])
  File "/Users/kiko1739/code/csds/venv_311/lib/python3.11/site-packages/jsii/_kernel/__init__.py", line 334, in create
    response = self.provider.create(
               ^^^^^^^^^^^^^^^^^^^^^
  File "/Users/kiko1739/code/csds/venv_311/lib/python3.11/site-packages/jsii/_kernel/providers/process.py", line 365, in create
    return self._process.send(request, CreateResponse)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/Users/kiko1739/code/csds/venv_311/lib/python3.11/site-packages/jsii/_kernel/providers/process.py", line 342, in send
    raise RuntimeError(resp.error) from JavaScriptError(resp.stack)
RuntimeError: Expected JSON path to start with '$', got: States.Format('LogStreamName: {}', $.Cause.Container.LogStreamName)

Subprocess exited with error 1

Reproduction Steps

# adapted from https://github.com/aws-samples/aws-cdk-examples/blob/main/python/stepfunctions/stepfunctions/stepfunctions_stack.py

from aws_cdk import (
    aws_stepfunctions as _aws_stepfunctions,
    App, Duration, Stack
)

class JobPollerStack(Stack):
    def __init__(self, app: App, id: str, **kwargs) -> None:
        super().__init__(app, id, **kwargs)

        # Step functions Definition

        submit_job = _aws_stepfunctions.Wait(
            self, "Submit Job",
            time=_aws_stepfunctions.WaitTime.duration(
                Duration.seconds(30))
        )

        wait_job = _aws_stepfunctions.Wait(
            self, "Wait 30 Seconds",
            time=_aws_stepfunctions.WaitTime.duration(
                Duration.seconds(30))
        )

        status_job = _aws_stepfunctions.Wait(
            self, "Get Status",
            time=_aws_stepfunctions.WaitTime.duration(
                Duration.seconds(30))
        )

        error_path = "$.Cause.Attempts[0].StatusReason"
        cause_path = "States.Format('LogStreamName: {}', $.Cause.Container.LogStreamName)"
        fail_job = _aws_stepfunctions.Fail(
            self, "Fail",
            error_path=error_path,  # works
            cause_path=cause_path  # fails
        )

        succeed_job = _aws_stepfunctions.Succeed(
            self, "Succeeded",
            comment='AWS Batch Job succeeded'
        )

        # Create Chain

        chain = submit_job.next(wait_job) \
            .next(status_job) \
            .next(_aws_stepfunctions.Choice(self, 'Job Complete?')
                  .when(_aws_stepfunctions.Condition.string_equals('$.status', 'FAILED'), fail_job)
                  .when(_aws_stepfunctions.Condition.string_equals('$.status', 'SUCCEEDED'), succeed_job)
                  .otherwise(wait_job))

        # Create state machine
        sm = _aws_stepfunctions.StateMachine(
            self, "StateMachine",
            definition_body=_aws_stepfunctions.DefinitionBody.from_chainable(chain),
            timeout=Duration.minutes(5),
        )

# in app.py:
# job_poller_stack = JobPollerStack(app, 'BadStack')

error_path works as given, cause_path doesn't.

Possible Solution

I'm guessing that cdk simply doesn't implement this AWS feature yet, since CausePath and ErrorPath were implemented only about 9/2023. If so, please consider this a vote for supporting it.

Additional Information/Context

No response

CDK CLI Version

CDK 2.140.0 (build 46168aa)

Framework Version

No response

Node.js Version

v20.12.1

OS

ProductName: MacOS ProductVersion: 14.3.1 BuildVersion: 23D60

Language

Python

Language Version

Python (3.11.9)

Other information

No response

@kimyx kimyx added bug This issue is a bug. needs-triage This issue or PR still needs to be triaged. labels May 5, 2024
@github-actions github-actions bot added the @aws-cdk/aws-lambda Related to AWS Lambda label May 5, 2024
@kimyx
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kimyx commented May 5, 2024

We can probably work around this issue by inserting a Pass state before the Fail state. The Pass state selects fields and formats error/cause strings to the output that becomes input to the Fail state, which can then use a simple selection to get what it needs. Will try it soon.

@kimyx
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kimyx commented May 6, 2024

I should say, it doesn't work using the cause keyword either. With this change:

        fail_job = _aws_stepfunctions.Fail(
            self, "Fail",
            error_path=error_path,  # works
            cause=cause_path  # fails
        )

The cdk deploy command oddly fails like this:

No stacks match the name(s) JobPollerStack

In my full code, it seems to deploy, but it fails when actually running the step function.

@kimyx
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kimyx commented May 6, 2024

This now works in my real app:

        error_parameters = {
            "Cause.$": "States.StringToJson($.Cause)",
        }
        # this state converts escaped json into a json object suitable for selections in the next state
        error_state = sfn.Pass(self, f'ConvertErrorCause_{error_task_identifier}', 
                                               parameters=error_parameters)

        format_parameters = {
            "ErrorMsg.$": "States.Format('Step Function Fail: {}', $.Cause.Attempts[0].StatusReason)",
            "CauseMsg.$": "States.Format('LogStreamName: {}', $.Cause.Container.LogStreamName)",
        }
        # this state formats error and cause strings for the following states
        format_state = sfn.Pass(self, f'FormatErrorCause_{error_task_identifier}', 
                                                  parameters=format_parameters)

        subject = sfn.JsonPath.string_at("$.ErrorMsg")
        message = sfn.TaskInput.from_text(sfn.JsonPath.string_at("$.CauseMsg"))

        # SNS publish error message
        failed_job_sns_topic = tasks.SnsPublish(self,
                                                f'FailedJobMessage_{error_task_identifier}',
                                                topic=sns_topic,
                                                subject=subject,
                                                message=message,
                                                result_path="$.result"
                                                )

        error_path = "$.ErrorMsg"
        cause_path = "$.CauseMsg"
        fail_state = sfn.Fail(self, f"FailStepFunction_{error_task_identifier}",
                              error_path=error_path,
                              cause_path=cause_path
                              )

        map_state.add_catch(error_state.next(format_state).next(failed_job_sns_topic).next(fail_state))

@ashishdhingra ashishdhingra self-assigned this May 6, 2024
@ashishdhingra ashishdhingra added needs-reproduction This issue needs reproduction. and removed needs-triage This issue or PR still needs to be triaged. labels May 6, 2024
@ashishdhingra
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@kimyx Good afternoon. I'm unsure if this issue is specific to CDK using Python. I tried reproducing the issue using both TypeScript and Python, they both produce the same error.

TypeScript

CDK stack

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

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

    const submit_job = new stepfunctions.Wait(this, "Submit Job", {
      time: stepfunctions.WaitTime.duration(cdk.Duration.seconds(30))
    });

    const wait_job = new stepfunctions.Wait(this, "Wait 30 Seconds", {
      time: stepfunctions.WaitTime.duration(cdk.Duration.seconds(30))
    });

    const status_job = new stepfunctions.Wait(this, "Get Status", {
      time: stepfunctions.WaitTime.duration(cdk.Duration.seconds(30))
    });

    const error_path = "$.Cause.Attempts[0].StatusReason"
    const cause_path = "States.Format('LogStreamName: {}', $.Cause.Container.LogStreamName)"
    const fail_job = new stepfunctions.Fail(this, "Fail", {
      errorPath: error_path,
      causePath: cause_path
    });

    const succeed_job = new stepfunctions.Succeed(this, "Succeeded", {
      comment: "AWS Batch Job succeeded"
    });

    // Create Chain
    const chain = submit_job.next(wait_job)
      .next(status_job)
      .next(new stepfunctions.Choice(this, 'Job Complete?')
        .when(stepfunctions.Condition.stringEquals('$.status', 'FAILED'), fail_job)
        .when(stepfunctions.Condition.stringEquals('$.status', 'SUCCEEDED'), succeed_job)
        .otherwise(wait_job));

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

cdk synth error

Error: Expected JSON path to start with '$', got: States.Format('LogStreamName: {}', $.Cause.Container.LogStreamName)
    at renderJsonPath (/Users/ashdhin/dev/repros/cdk/issue30063_stepfunction/typescript/node_modules/aws-cdk-lib/aws-stepfunctions/lib/states/state.js:1:9755)
    at Fail.toStateJson (/Users/ashdhin/dev/repros/cdk/issue30063_stepfunction/typescript/node_modules/aws-cdk-lib/aws-stepfunctions/lib/states/fail.js:1:1050)
    at StateGraph.toGraphJson (/Users/ashdhin/dev/repros/cdk/issue30063_stepfunction/typescript/node_modules/aws-cdk-lib/aws-stepfunctions/lib/state-graph.js:1:2159)
    at ChainDefinitionBody.bind (/Users/ashdhin/dev/repros/cdk/issue30063_stepfunction/typescript/node_modules/aws-cdk-lib/aws-stepfunctions/lib/state-machine.js:1:12008)
    at new StateMachine (/Users/ashdhin/dev/repros/cdk/issue30063_stepfunction/typescript/node_modules/aws-cdk-lib/aws-stepfunctions/lib/state-machine.js:1:6368)
    at new TypescriptStack (/Users/ashdhin/dev/repros/cdk/issue30063_stepfunction/typescript/lib/typescript-stack.ts:41:16)
    at Object.<anonymous> (/Users/ashdhin/dev/repros/cdk/issue30063_stepfunction/typescript/bin/typescript.ts:7:1)
    at Module._compile (node:internal/modules/cjs/loader:1376:14)
    at Module.m._compile (/Users/ashdhin/dev/repros/cdk/issue30063_stepfunction/typescript/node_modules/ts-node/src/index.ts:1618:23)
    at Module._extensions..js (node:internal/modules/cjs/loader:1435:10)
Python

CDK stack

from aws_cdk import (
    Duration,
    Stack,
    aws_stepfunctions as stepfunctions,
)
from constructs import Construct

class PythonStack(Stack):

    def __init__(self, scope: Construct, construct_id: str, **kwargs) -> None:
        super().__init__(scope, construct_id, **kwargs)

        submit_job = stepfunctions.Wait(
            self, "Submit Job",
            time=stepfunctions.WaitTime.duration(
                Duration.seconds(30))
        )

        wait_job = stepfunctions.Wait(
            self, "Wait 30 Seconds",
            time=stepfunctions.WaitTime.duration(
                Duration.seconds(30))
        )

        status_job = stepfunctions.Wait(
            self, "Get Status",
            time=stepfunctions.WaitTime.duration(
                Duration.seconds(30))
        )

        error_path = "$.Cause.Attempts[0].StatusReason"
        cause_path = "States.Format('LogStreamName: {}', $.Cause.Container.LogStreamName)"
        fail_job = stepfunctions.Fail(
            self, "Fail",
            error_path=error_path,  # works
            cause_path=cause_path  # fails
        )

        succeed_job = stepfunctions.Succeed(
            self, "Succeeded",
            comment='AWS Batch Job succeeded'
        )

        # Create Chain
        chain = submit_job.next(wait_job) \
            .next(status_job) \
            .next(stepfunctions.Choice(self, 'Job Complete?')
                  .when(stepfunctions.Condition.string_equals('$.status', 'FAILED'), fail_job)
                  .when(stepfunctions.Condition.string_equals('$.status', 'SUCCEEDED'), succeed_job)
                  .otherwise(wait_job))

        # Create state machine
        sm = stepfunctions.StateMachine(
            self, "StateMachine",
            definition_body=stepfunctions.DefinitionBody.from_chainable(chain),
            timeout=Duration.minutes(5),
        )

cdk synth error

jsii.errors.JavaScriptError: 
  Error: Expected JSON path to start with '$', got: States.Format('LogStreamName: {}', $.Cause.Container.LogStreamName)
      at renderJsonPath (/var/folders/r5/964t6ckn7jl87krdykn_3hrm0000gr/T/jsii-kernel-fWOjiH/node_modules/aws-cdk-lib/aws-stepfunctions/lib/states/state.js:1:9755)
      at Fail.toStateJson (/var/folders/r5/964t6ckn7jl87krdykn_3hrm0000gr/T/jsii-kernel-fWOjiH/node_modules/aws-cdk-lib/aws-stepfunctions/lib/states/fail.js:1:1050)
      at StateGraph.toGraphJson (/var/folders/r5/964t6ckn7jl87krdykn_3hrm0000gr/T/jsii-kernel-fWOjiH/node_modules/aws-cdk-lib/aws-stepfunctions/lib/state-graph.js:1:2159)
      at ChainDefinitionBody.bind (/var/folders/r5/964t6ckn7jl87krdykn_3hrm0000gr/T/jsii-kernel-fWOjiH/node_modules/aws-cdk-lib/aws-stepfunctions/lib/state-machine.js:1:12008)
      at new StateMachine (/var/folders/r5/964t6ckn7jl87krdykn_3hrm0000gr/T/jsii-kernel-fWOjiH/node_modules/aws-cdk-lib/aws-stepfunctions/lib/state-machine.js:1:6368)
      at Kernel._Kernel_create (/private/var/folders/r5/964t6ckn7jl87krdykn_3hrm0000gr/T/tmpadel18q6/lib/program.js:10119:25)
      at Kernel.create (/private/var/folders/r5/964t6ckn7jl87krdykn_3hrm0000gr/T/tmpadel18q6/lib/program.js:9790:93)
      at KernelHost.processRequest (/private/var/folders/r5/964t6ckn7jl87krdykn_3hrm0000gr/T/tmpadel18q6/lib/program.js:11707:36)
      at KernelHost.run (/private/var/folders/r5/964t6ckn7jl87krdykn_3hrm0000gr/T/tmpadel18q6/lib/program.js:11667:22)

@kimyx Please advise on how you were able to come up with expression $.Cause.Container.LogStreamName.

Thanks,
Ashish

@ashishdhingra ashishdhingra added investigating This issue is being investigated and/or work is in progress to resolve the issue. and removed needs-reproduction This issue needs reproduction. labels May 6, 2024
@kimyx
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kimyx commented May 6, 2024

Thanks for confirming, Ashish.

The LogStreamName expression comes from my real app, which uses a step function to start Batch jobs, each of which produces a log stream. I didn't know a good expression for the sample app, but it failed with the same error my real app was getting. Once the initial error is fixed, let me know if you want help finding an applicable expression to test.

@ashishdhingra
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Looks like as reported in the issue description, per StepFunctions: States: Fail documentation, using CausePath should support an intrinsic function that returns a string. However, it's returning the mentioned error, perhaps here.

@ashishdhingra ashishdhingra added p2 effort/small Small work item – less than a day of effort p1 and removed investigating This issue is being investigated and/or work is in progress to resolve the issue. p2 labels May 7, 2024
@sakurai-ryo
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I am working on this issue.

@ashishdhingra ashishdhingra removed their assignment May 14, 2024
@mergify mergify bot closed this as completed in #30210 May 30, 2024
mergify bot pushed a commit that referenced this issue May 30, 2024
)

### 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

```ts
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
- [x] My code adheres to the [CONTRIBUTING GUIDE](https://github.com/aws/aws-cdk/blob/main/CONTRIBUTING.md) and [DESIGN GUIDELINES](https://github.com/aws/aws-cdk/blob/main/docs/DESIGN_GUIDELINES.md)

----

*By submitting this pull request, I confirm that my contribution is made under the terms of the Apache-2.0 license*
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atanaspam pushed a commit to atanaspam/aws-cdk that referenced this issue Jun 3, 2024
…#30210)

### Issue # (if applicable)

Closes aws#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

```ts
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
- [x] My code adheres to the [CONTRIBUTING GUIDE](https://github.com/aws/aws-cdk/blob/main/CONTRIBUTING.md) and [DESIGN GUIDELINES](https://github.com/aws/aws-cdk/blob/main/docs/DESIGN_GUIDELINES.md)

----

*By submitting this pull request, I confirm that my contribution is made under the terms of the Apache-2.0 license*
vdahlberg pushed a commit to vdahlberg/aws-cdk that referenced this issue Jun 10, 2024
…#30210)

### Issue # (if applicable)

Closes aws#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

```ts
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
- [x] My code adheres to the [CONTRIBUTING GUIDE](https://github.com/aws/aws-cdk/blob/main/CONTRIBUTING.md) and [DESIGN GUIDELINES](https://github.com/aws/aws-cdk/blob/main/docs/DESIGN_GUIDELINES.md)

----

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