TypeError (yield* ... is not iterable) while running Pact provider tests on Node.js with Express

Question

I've been trying to implement Pact in a React-Node/Express project. In the provider tests, I'm running into a strange error that I couldn't find explained online. My provider interactions are all passing, but at the end of the output I get the below error, which makes the test suite end with a failure despite all the tests passing

TypeError: yield* (intermediate value)(intermediate value)(intermediate value)(intermediate value) is not iterable

  at loadOneConfig (node_modules/@babel/core/lib/config/files/configuration.js:146:37)
      at loadOneConfig.next (<anonymous>)
  at buildRootChain (node_modules/@babel/core/lib/config/config-chain.js:82:51)
      at buildRootChain.next (<anonymous>)
  at loadPrivatePartialConfig (node_modules/@babel/core/lib/config/partial.js:103:62)
      at loadPrivatePartialConfig.next (<anonymous>)
  at loadFullConfig (node_modules/@babel/core/lib/config/full.js:57:46)
      at loadFullConfig.next (<anonymous>)
  at Function.<anonymous> (node_modules/@babel/core/lib/config/index.js:35:43)
  at evaluateSync (node_modules/gensync/index.js:251:28)
  at Function.sync (node_modules/gensync/index.js:89:14)
  at node_modules/@babel/core/lib/config/index.js:47:61
  at OptionManager.init (node_modules/@babel/core/lib/index.js:257:36)
  at Object.<anonymous>.exports.transformSync (node_modules/@babel/register/lib/worker/transform.js:80:44)
  at Function.handleMessage (node_modules/@babel/register/lib/worker/handle-message.js:23:16)
  at LocalClient.<anonymous> (node_modules/@babel/register/lib/worker-client.js:134:86)
  at LocalClient.transform (node_modules/@babel/register/lib/worker-client.js:64:47)
  at compile (node_modules/@babel/register/lib/hook.js:58:25)
  at compileBabel7 (node_modules/@babel/register/lib/hook.js:49:14)
  at Module._compile (node_modules/pirates/lib/index.js:130:29)

Here's the provider test file, which I'm running in Docker so that I can run the tests against a Postgres test database

import app from "../../server/server";
import { Verifier } from "@pact-foundation/pact";
import path from "path";
import { cleanupDatabase } from "../../server/testHelpers/requestTestHelpers";
import models from "../../server/policeDataManager/models";
import Case from "../../sharedTestHelpers/case";
import Officer from "../../sharedTestHelpers/officer";
import CaseOfficer from "../../sharedTestHelpers/caseOfficer";
import { CASE_STATUS, COMPLAINANT } from "../../sharedUtilities/constants";
import IntakeSource from "../../server/testHelpers/intakeSource";
import ReferralLetter from "../../server/testHelpers/ReferralLetter";
import { updateCaseStatus } from "../../server/handlers/data/queries/queryHelperFunctions";
import { random } from "lodash";

jest.mock(
  "../../server/handlers/cases/referralLetters/sharedLetterUtilities/uploadLetterToS3",
  () => jest.fn()
);

const setupCase = async () => {
  try {
    models.cases.destroy({ where: {}, truncate: true, auditUser: "user" });

    const intakeSource = await models.intake_source.create(
      new IntakeSource.Builder().defaultIntakeSource().withId(random(5, 99999)),
      { auditUser: "user" }
    );

    const c = await models.cases.create(
      new Case.Builder()
        .defaultCase()
        .withId(1)
        .withComplaintType("Civilian Within NOPD Initiated")
        .withIntakeSourceId(intakeSource.id),
      {
        auditUser: "user"
      }
    );

    const officer = await models.officer.create(
      new Officer.Builder().defaultOfficer(),
      { auditUser: "user" }
    );

    const case_officer = await models.case_officer.create(
      new CaseOfficer.Builder()
        .defaultCaseOfficer()
        .withOfficerId(officer.id)
        .withCaseId(c.id)
        .withRoleOnCase(COMPLAINANT),
      { auditUser: "user" }
    );

    return c;
  } catch (e) {
    console.log(e);
  }
};

const setupLetter = async letterCase => {
  try {
    await updateCaseStatus(letterCase, CASE_STATUS.READY_FOR_REVIEW);

    const letter = await models.referral_letter.create(
      new ReferralLetter.Builder()
        .defaultReferralLetter()
        .withCaseId(letterCase.id)
        .withRecipient("King of all police")
        .withRecipientAddress("100 Main Street, North Pole")
        .withSender("The aggrieved party"),
      { auditUser: "user" }
    );
  } catch (e) {
    console.log(e);
  }
};

describe("Pact Verification", () => {
  let server;
  beforeAll(() => {
    server = app.listen(8989);
  });

  afterAll(async () => {
    await cleanupDatabase();
    await models.sequelize.close();
    await server.close();
  });

  test("validates the expectations of get case details", async () => {
    const opts = {
      logLevel: "INFO",
      providerBaseUrl: "http://localhost:8989",
      provider: "police-data-manager.server",
      providerVersion: "1.0.0",
      pactUrls: [
        path.resolve(
          __dirname,
          "../../../pact/pacts/police-data-manager.client-police-data-manager.server.json"
        )
      ],
      stateHandlers: {
        "Case exists": async () => {
          await cleanupDatabase();
          await setupCase();
        },
        "letter is ready for review": async () => {
          await cleanupDatabase();
          const letterCase = await setupCase();
          await setupLetter(letterCase);
        },
        "edit letter": async () => {
          const letterCase = await setupCase();
          await setupLetter(letterCase);
        }
      }
    };

    const output = await new Verifier(opts).verifyProvider();
    console.log(output);
  });
});

I've tried wrapping various parts of the code in try/catch blocks to localize the problem, but with no luck. I've also tweaked the code in my node_modules to get a better look at the problem

loadOneConfig in @babel/core/lib/config/files/configuration.js

function* loadOneConfig(names, dirname, envName, caller, previousConfig = null) {
  const configs = yield* _gensync().all(names.map(filename => readConfig(_path().join(dirname, filename), envName, caller)));
  const config = configs.reduce((previousConfig, config) => {
    if (config && previousConfig) {
      throw new Error(`Multiple configuration files found. Please remove one:\n` + ` - ${_path().basename(previousConfig.filepath)}\n` + ` - ${config.filepath}\n` + `from ${dirname}`);
    }

    return config || previousConfig;
  }, previousConfig);

  if (config) {
    debug("Found configuration %o from %o.", config.filepath, dirname);
  }

  return config;
}

When I moved code around to console.log it, I get the new error that _gensync().all is not a function and console.logging _gensync() returns an empty object.

I tried upgrading my babel to the latest version, but it did not seem to have any effect.