asl-validator/src/checks/duplicate-payload-template-fields.ts

Amazon States Language validator

import { JSONPath } from "jsonpath-plus";
import { AslChecker, StateMachineError, StateMachineErrorCode } from "../types";

// From the ASL spec:
// > A JSON object MUST NOT have duplicate field names after fields
// > ending with the characters ".$" are renamed to strip the ".$" suffix.
export const mustNotHaveDuplicateFieldNamesAfterEvaluation: AslChecker = (
  definition
) => {
  // find each `Parameters` or `ResultSelector` field
  // for each one, examine each node's children for field names
  // that will be in conflict after evaluation.
  const errorMessages: StateMachineError[] = [];
  const valuesToInspect: Record<string, unknown>[] = JSONPath<
    Record<string, unknown>[]
  >({
    json: definition,
    path: `$..[Parameters,ResultSelector]`,
  });

  const inspectKeys = (parent: Record<string, unknown>): void => {
    const keys: Record<string, number> = {};
    Object.keys(parent).forEach((key) => {
      const keyPostEval = key.endsWith(".$")
        ? key.substring(0, key.length - 2)
        : key;
      const current = keys[keyPostEval];
      if (current) {
        errorMessages.push({
          "Error code": StateMachineErrorCode.DuplicateFieldName,
          Message: `A duplicate field will exist after renaming to strip the ".$" suffix from: ${key}.$`,
        });
      }
      keys[keyPostEval] = current ? current + 1 : 1;
      if (!!parent[key] && typeof parent[key] === "object") {
        inspectKeys(parent[key] as Record<string, unknown>);
      }
    });
  };

  valuesToInspect.forEach((parent) => inspectKeys(parent));
  return errorMessages;
};