asl-validator/src/checks/missing-terminal-state-errors.ts

Amazon States Language validator

import { AslChecker, StateMachineError, StateMachineErrorCode } from "../types";
import { getStatesContainer } from "./get-states";

export const missingTerminalStateErrors: AslChecker = (definition) => {
  const errorMessages: StateMachineError[] = [];
  // find each enclosed state machine and verify that
  // each state machine contains at least one of the following:
  // - state with End: true
  // - state with Type: Succeed
  // - state with Type: Fail
  const terminals: Record<string, number> = {};
  let fsmId = 1;
  getStatesContainer(definition).forEach((states) => {
    const fsmKey = `fsm${fsmId}`;
    // initialize the nested fsm to have a terminal count of zero
    terminals[fsmKey] = 0;
    // check each of its states to see if the fsm terminates
    Object.values(states).forEach((state) => {
      const count = terminals[fsmKey];
      if (
        ["Succeed", "Fail"].indexOf(state.Type as string) !== -1 ||
        state.End
      ) {
        terminals[fsmKey] = count ? count + 1 : 1;
      }
    });
    fsmId += 1;
  });
  for (const [key, value] of Object.entries(terminals)) {
    if (value === 0) {
      errorMessages.push({
        "Error code": StateMachineErrorCode.MissingTerminalState,
        // better to have a line number here
        Message: `State machine ${key} is missing a terminal state`,
      });
    }
  }

  return errorMessages;
};