jest trying to transform a file in node_modules (worked in a previous version)

Question

I had jest v27.2.4 and ts-jest v27.0.5 and tests worked on, on the latest versions (I think they are 27.4.x) tests don't run anymore since jest complains about a .js file inside node_modules

I tried to downgrade by setting the specific version in package.json (i.e. without the ^) but since jest itself has dependencies on other libraries with ^ it is still upgrading them

The error when running the tests:

Jest encountered an unexpected token

    Jest failed to parse a file. This happens e.g. when your code or its dependencies use non-standard JavaScript syntax, or when Jest is not configured to support such syntax.

    By default "node_modules" folder is ignored by transformers.

    Details:

    /home/me/code/node_modules/@middy/core/index.js:2
      plugin?.beforePrefetch?.()
             ^

    SyntaxError: Unexpected token '.'

      1 | import { logger } from "@libs/logger";
    > 2 | import middy from "@middy/core";
        | ^
      at Runtime.createScriptFromCode (../../../node_modules/jest-runtime/build/index.js:1728:14)
      at Object.<anonymous> (../../libs/middleware/src/index.ts:2:1)

my jest.config.js file:

module.exports = {
  //clearMocks: true,
  //coverageDirectory: "coverage",
  //collectCoverage: true,
  verbose: true,
  globals: {
    "ts-jest": {
      tsconfig: "tsconfig.json",
    },
  },
  modulePathIgnorePatterns: ["dist"],
  transform: {
    "^.+\\.(ts|tsx)$": "ts-jest",
  },
  testEnvironment: "node",
  testMatch: ["**/__tests__/*.+(ts|tsx|js)", "**/*.spec.+(ts|tsx|js)"],
};

my tsconfig.json file:

{
  "$schema": "https://json.schemastore.org/tsconfig",
  "display": "Node 14",
  "compilerOptions": {
    "incremental": true,
    "target": "ES2019",
    "module": "commonjs",
    "lib": [
      "ES2019"
    ],
    "declaration": true,
    "sourceMap": true,
    "composite": false,
    "removeComments": true,
    "strict": true,
    "noImplicitAny": true,
    "strictNullChecks": true,
    "strictFunctionTypes": true,
    "strictBindCallApply": true,
    "strictPropertyInitialization": true,
    "noImplicitThis": true,
    "moduleResolution": "node",
    "types": [
      "node"
    ],
    "esModuleInterop": true,
    "skipLibCheck": true,
    "experimentalDecorators": true,
    "emitDecoratorMetadata": true,
    "forceConsistentCasingInFileNames": true
  }
}

Any clues how to fix this?

jcts3 · Answer 1 · 2022-01-25T15:06:37.957

I had the same exact error message, though not in using jest but hopefully this fixes it for you too. Since both yours and mine highlighted Middy as the source of the error - i.e. from yours

    /home/me/code/node_modules/@middy/core/index.js:2
      plugin?.beforePrefetch?.()
             ^

    SyntaxError: Unexpected token '.'
             ^

and mine:

/.webpack/service/src/functions/functionName/handler.js:78292
  plugin?.beforePrefetch?.()
         ^

SyntaxError: Unexpected token '.'

To me this it seemed odd that there was optional chaining (object?.property), as this should be handled by the compiler before getting to a .js file (in Node 12 at least - it's different if you're using Node 14 and above).

Checking middy's most recent releases shows an upgrade to 2.5.7 yesterday, with the release message describing a recent transpiling error in 2.5.6 which is resolved by upgrade to 2.5.7. Upgrading my middy dependencies to 2.5.7 indeed eliminated this error for me, i.e. I no longer get an error when trying to call my code (in AWS Lambda for what it's worth).

This is what my dependencies in my package.json now look like:

...
"dependencies": {
    "@middy/core": "^2.5.7",
    "@middy/http-error-handler": "^2.5.7",
    "@middy/http-event-normalizer": "^2.5.7",
    "@middy/http-json-body-parser": "^2.5.7",
    "@middy/util": "^2.5.7"
  },
...

Whereas before they were:

...
"dependencies": {
    "@middy/core": "^2.5.3",
    "@middy/http-error-handler": "^2.5.4",
    "@middy/http-event-normalizer": "^2.5.4",
    "@middy/http-json-body-parser": "^2.5.4",
    "@middy/util": "^2.5.3"
  },
...

Where my package-lock.json had two of the middy packages on 2.5.6, which as mentioned above will have been the cause of the issue.

If middy isn't a dependency in your package.json and is a transitive dependency of something else, maybe try editing the middy version number in the package-lock.json itself to 2.5.7?

Your answer could be improved with additional supporting information. Please [edit] to add further details, such as citations or documentation, so that others can confirm that your answer is correct. You can find more information on how to write good answers [in the help center](/help/how-to-answer). — Community, Jan 25 '22 at 14:16

jest trying to transform a file in node_modules (worked in a previous version)

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