Adding a ResultPath to a Catch doesn't work unless you add one outside the catch too

[LL782]

What went wrong?
I had a state machine definition with a Catch on a Task. When I added a ResultPath to the Catcher I got an error when trying to deploy.

What did you expect should have happened?

I expected deployment to be successful and the catcher to use the ResultPath. Note, this is valid in the the JSON definition that appears in the AWS Console. There shoudn't be an error.

What was the config you used?

// ...

const serverlessConfiguration = {
  service: {
    name: "content-migration",
  },
  frameworkVersion: ">=1.72.0",
  custom: {
    webpack: {
      webpackConfig: "./webpack.config.js",
      includeModules: true,
    },
  },
  plugins: ["serverless-step-functions", "serverless-webpack"],
  provider: {
    name: "aws",
    region: "eu-west-1",
    runtime: "nodejs12.x",
    timeout: 60,
    environment: {
      AWS_NODEJS_CONNECTION_REUSE_ENABLED: "1",
    },
  },
  functions: {
    createImageInContentful: {
      handler: "src/titles/createImage.handler",
      description: "Create an image asset in Contentful",
      environment: { ...contentfulEnvironmentVariables },
    },
    publishImageInContentful: {
      handler: "src/titles/publishImage.handler",
      description: "Publish an image asset in Contentful",
      environment: { ...contentfulEnvironmentVariables },
    },
  },
  stepFunctions: {
    stateMachines: {
      migrateAllTitlesMainImage: {
        name: "MigrateAllTitlesMainImage",
        definition: {
          Comment: "Migrate images from titles from Airtable into Contentful",
          StartAt: "MigrateAll",
          States: {
            MigrateAll: {
              Type: "Map",
              End: true,
              ItemsPath: "$.titles",
              Iterator: {
                StartAt: "CreateContentfulAsset",
                States: {
                  CreateContentfulAsset: {
                    Type: "Task",
                    Next: "PublishContentfulAsset",
                    Resource: {
                      "Fn::GetAtt": ["createImageInContentful", "Arn"],
                    },
                    Catch: [
                      {
                        ErrorEquals: ["VersionMismatch"],
                        ResultPath: "$.CreateContentfulAssetError",
                        Next: "AssetAlreadyCreated",
                      },
                    ],
                  },
                  AssetAlreadyCreated: {
                    Type: "Pass",
                    Next: "PublishContentfulAsset",
                  },
                  PublishContentfulAsset: {
                    Type: "Task",
                    End: true,
                    Resource: {
                      "Fn::GetAtt": ["publishImageInContentful", "Arn"],
                    },
                  },
                },
              },
            },
          },
        },
      },
    },
    activities: ["content-migration-titles-images"],
    validate: true,
  },
};

module.exports = serverlessConfiguration;

What stacktrace or error message from your provider did you see?

I got this in the console after running serverless deploy

Serverless Error ---------------------------------------

✕ State machine "migrateAllTitlesMainImage" definition is invalid:
undefined: undefined
No errors

Additional Data

• Serverless Framework Core Version you're using: 1.78.1
• The Plugin Version you're using: 2.22.1
• Operating System: MacOS
• Stack Trace: n/a
• Provider Error messages: see above

Note

I notice in your example there is a ResultPath for the state itself. Adding this to my task makes the issue go away

CreateContentfulAsset: {
  Type: "Task",
  Next: "PublishContentfulAsset",
  Resource: {
    "Fn::GetAtt": ["createImageInContentful", "Arn"],
  },
  Catch: [
    {
      ErrorEquals: ["VersionMismatch"],
      ResultPath: "$.CreateContentfulAssetError",
      Next: "AssetAlreadyCreated",
    },
  ],
+  ResultPath: "$.CreateContentfulAssetResult",
},

I think that either this should be fixed (to stay in sync with what works in AWS) or a more informative error should be output to save time for anyone who hits this error.

BTW thanks for a great plugin.

[theburningmonk]

@LL782 turn turning off validate for now, it's relying on another project asl-validator which might be behind on the official spec.

I've used ResultPath with Catch before and it definitely works.

[LL782]

@theburningmonk that's great info. thanks!

I'll perhaps take my issue to asl-validator

[theburningmonk]

@LL782 I've made a PR there already, once it gets merged I'll update the dependency here and it should be sorted then.