AWS Step Functions StateMachine Language JSONPath Gotchas

input.json

{
  "a": {
    "v": 1
  },
  "b": {
    "v": 2
  },
  "c": {
    "v": 3
  }
}

statemachines.md

JSONPath Quirks

Pass - InputPath - NonLeaf MultiProps Selection

Definition

💥 serverless-framework
❇️ AWS Console

{
  "StartAt": "Step0",
  "States": {
    "Step0": {
      "Type": "Pass",
      "InputPath": "$['a', 'b'].v",
      "ResultPath": "$.stateOutput.Step0",
      "End": true
    }
  }
}

Output (:boom:)

Serverless Famework Error:

 Serverless Error ----------------------------------------
 
  ✕ State machine "example1" definition is invalid:
  Lexical error on line 1. Unrecognized text.
  $['a', 'b'].v
  ------^

AWS Console Error:

{
  "error": "States.Runtime",
  "cause": "An error occurred while executing the state 'Step0' (entered at the event id #2). Invalid path '$['a', 'b'].v' : Multi properties can only be used as path leafs: $['a', 'b']"
}

Pass - InputPath - Leaf MultiProps Selection

Definition

❇️ serverless-framework
❇️ AWS Console

Changing InputPath: $['a', 'b'] in the Console works and produces:

{
  "StartAt": "Step0",
  "States": {
    "Step0": {
      "Type": "Pass",
      "InputPath": "$['a', 'b']",
      "ResultPath": "$.stateOutput.Step0",
      "End": true
    }
  }
}

Output (:boom:)

💥 serverless-framework
❇️ AWS Console

{
  "a": {
    "v": 1
  },
  "b": {
    "v": 2
  },
  "c": {
    "v": 3
  },
  "stateOutput": {
    "Step0": {
      "a": {
        "v": 1
      },
      "b": {
        "v": 2
      }
    }
  }
}

The MultiProperty syntax still throws the same error in serverless framework when trying to deploy

 Serverless Error ----------------------------------------
 
  ✕ State machine "example1" definition is invalid:
  Lexical error on line 1. Unrecognized text.
  $['a', 'b']
  ------^

Pass - InputPath - WildCard Operator

Definition

❇️ serverless-framework
❇️ AWS Console

{
  "StartAt": "Step0",
  "States": {
    "Step0": {
      "Type": "Pass",
      "InputPath": "$[*].v",
      "ResultPath": "$.stateOutput.Step0",
      "End": true
    }
  }
}

Output (:sparkle:)

❇️ serverless-framework
❇️ AWS Console

{
  "a": {
    "v": 1
  },
  "b": {
    "v": 2
  },
  "c": {
    "v": 3
  },
  "stateOutput": {
    "Step0": [
      1,
      2,
      3
    ]
  }
}

Pass - Parameters - Leaf MultiProps Selection

Definition

❇️ serverless-framework
❇️ AWS Console

{
  "StartAt": "Step0",
  "States": {
    "Step0": {
      "Type": "Pass",
      "Parameters": {
        "params.$": "$['a', 'b']"
      },
      "ResultPath": "$.stateOutput.Step0",
      "End": true
    }
  }
}

Output (:sparkle:)

❇️ serverless-framework
❇️ AWS Console

{
  "a": {
    "v": 1
  },
  "b": {
    "v": 2
  },
  "c": {
    "v": 3
  },
  "stateOutput": {
    "Step0": {
      "params": {
        "a": {
          "v": 1
        },
        "b": {
          "v": 2
        }
      }
    }
  }
}

Pass - Parameters - NonLeaf MultiProps Selection

Definition

❇️ serverless-framework
❇️ AWS Console

{
  "StartAt": "Step0",
  "States": {
    "Step0": {
      "Type": "Pass",
      "Parameters": {
        "params.$": "$['a', 'b'].v"
      },
      "ResultPath": "$.stateOutput.Step0",
      "End": true
    }
  }
}

Output (:boom:)

{
  "error": "States.Runtime",
  "cause": "An error occurred while executing the state 'Step0' (entered at the event id #2). The JSONPath '$['a', 'b'].v' specified for the field 'params.$' could not be found in the input '{\"a\":{\"v\":1},\"b\":{\"v\":2},\"c\":{\"v\":3}}'"
}

Pass - Parameters - NonLeaf - WildCard Operator

Definition

❇️ serverless-framework
❇️ AWS Console

{
  "StartAt": "Step0",
  "States": {
    "Step0": {
      "Type": "Pass",
      "Parameters": {
        "params.$": "$[*].v"
      },
      "ResultPath": "$.stateOutput.Step0",
      "End": true
    }
  }
}

Output (:sparkle:)

{
  "a": {
    "v": 1
  },
  "b": {
    "v": 2
  },
  "c": {
    "v": 3
  },
  "stateOutput": {
    "Step0": {
      "params": [
        1,
        2,
        3
      ]
    }
  }
}

Pass - Result - Reference Parameters

Definition

{
  "StartAt": "Step0",
  "States": {
    "Step0": {
      "Type": "Pass",
      "Parameters": {
        "params.$": "$[*].v"
      },
      "Result": {
        "result_params.$": "$.params"
      },
      "ResultPath": "$.stateOutput.Step0",
      "End": true
    }
  }
}

Output

Didn't go as planned.... 😒 ...doesn't seem as if Result field accepts a JSONPath (Path, or Reference Path) 🤔

{
  "a": {
    "v": 1
  },
  "b": {
    "v": 2
  },
  "c": {
    "v": 3
  },
  "stateOutput": {
    "Step0": {
      "result_params.$": "$.params"
    }
  }
}