Regression in 2.1.2: a transform must export a process or processAsync function.

[rmunn]

Just updated svelte-jester from 2.1.1 to 2.1.2 and now my tests won't run. "TypeError: Jest: a transform must export a process or processAsync function." Reverting back to 2.1.1 makes the tests run again.

I inserted some console.log calls into the loadTransformers() function from jest-transform and found that it ran three times. The first two times, it went through this block, but the third time it didn't:

if (typeof transformer.createTransformer === 'function') {
  transformer = transformer.createTransformer(transformerConfig);
}

I inserted console.log(transformer) calls before and after that block, and got the following:

First pass

Before:

{
  canInstrument: true,
  getCacheKey: [Function: getCacheKey],
  getCacheKeyAsync: [AsyncFunction: getCacheKeyAsync],
  process: [Function: process],
  processAsync: [AsyncFunction: processAsync],
  createTransformer: [Function: createTransformer]
}

After:

{
  canInstrument: true,
  getCacheKey: [Function: getCacheKey],
  getCacheKeyAsync: [AsyncFunction: getCacheKeyAsync],
  process: [Function: process],
  processAsync: [AsyncFunction: processAsync]
}

Second pass

Before:

{ createTransformer: [Function: createTransformer] }

After:

TsJestTransformer {
  _depGraphs: Map(0) {},
  _watchMode: false,
  _logger: [Function: log] {
    child: [Function (anonymous)],
    wrap: [Function (anonymous)],
    trace: [Function (anonymous)],
    debug: [Function: emptyFunction],
    info: [Function (anonymous)],
    warn: [Function (anonymous)],
    error: [Function (anonymous)],
    fatal: [Function (anonymous)]
  },
  getCacheKey: [Function: bound ],
  process: [Function: bound ]
}

Third pass

Before:

[Function: createTransformer]

After:

[Function: createTransformer]

I don't know why on the third pass, the transformer value is the createTransformer function instead of having a createTrasnformer property (i.e. it should be { createTransformer: [Function: createTransformer] } at that point). Being unfamiliar with the Jest code base, that's as far as I can get easily. But hopefully this will give you some idea of what part of the code might be causing this regression.

[rmunn]

Reproduction steps:

• Run npm init svelte@next
• Edit tsconfig.json to remove comments (so npx apply rossyman/svelte-add-jest won't throw)
• Run npx apply rossyman/svelte-add-jest
• Run npm install
• Run npm run test and see the exception that Jest throws

[sebastianrothe]

I will add some tests that mimic the usual usage to get this covered, finally.

[rmunn]

Can confirm that #75 fixes this issue for me.

[schicks]

This does not appear to be released yet. When can we expect a 2.1.3 with this fix? Right now we're using jest 25 because we can't get 27 to work until this is out.

[jakobrosenberg]

For anyone else waiting for 2.1.3, I cloned and published the master branch to svelte-jester-pre-fix. To use it you can temporarily add "svelte-jester": "npm:svelte-jester-pre-fix@^2.1.3" to your devDependencies until the official 2.1.3 has been released.

It has fixed all issues for me but YMMV.

[mihar-22]

Sorry about the delay, released 2.1.3!

[asode]

Thank you for the update! However, still having some issues: though not sure if I'm the only one, but still getting an error about the preprocess.js file:

 FAIL  src/components/Layout.test.ts
  ● Test suite failed to run

    Cannot find module './preprocess.js'
    Require stack:
    - /home/asode/coding/my-svelte-vite-test/node_modules/svelte-jester/dist/transformer.cjs
    - /home/asode/coding/my-svelte-vite-test/node_modules/jest-util/build/requireOrImportModule.js
    - /home/asode/coding/my-svelte-vite-test/node_modules/jest-util/build/index.js
    - /home/asode/coding/my-svelte-vite-test/node_modules/@jest/core/build/cli/index.js
    - /home/asode/coding/my-svelte-vite-test/node_modules/@jest/core/build/jest.js
    - /home/asode/coding/my-svelte-vite-test/node_modules/jest-cli/build/cli/index.js
    - /home/asode/coding/my-svelte-vite-test/node_modules/jest-cli/bin/jest.js
    - /home/asode/coding/my-svelte-vite-test/node_modules/jest/bin/jest.js

    Require stack:
      node_modules/svelte-jester/dist/transformer.cjs
      node_modules/jest-util/build/requireOrImportModule.js
      node_modules/jest-util/build/index.js
      node_modules/@jest/core/build/cli/index.js
      node_modules/@jest/core/build/jest.js
      node_modules/jest-cli/build/cli/index.js
      node_modules/jest-cli/bin/jest.js
      node_modules/jest/bin/jest.js

      at Object.processSync [as process] (node_modules/svelte-jester/dist/transformer.cjs:115:32)
      at ScriptTransformer.transformSource (node_modules/@jest/transform/build/ScriptTransformer.js:612:31)
      at ScriptTransformer._transformAndBuildScript (node_modules/@jest/transform/build/ScriptTransformer.js:758:40)
      at ScriptTransformer.transform (node_modules/@jest/transform/build/ScriptTransformer.js:815:19)

  "devDependencies": {
    "@sveltejs/vite-plugin-svelte": "^1.0.0-next.24",
    "@testing-library/jest-dom": "^5.14.1",
    "@testing-library/svelte": "^3.0.3",
    "@tsconfig/svelte": "^2.0.1",
    "@types/cssnano": "^4.0.1",
    "@types/jest": "^27.0.1",
    "@typescript-eslint/eslint-plugin": "^4.31.1",
    "@typescript-eslint/parser": "^4.31.1",
    "autoprefixer": "^10.3.4",
    "cssnano": "^5.0.8",
    "eslint-plugin-svelte3": "^3.2.1",
    "jest": "^27.2.0",
    "postcss": "^8.3.6",
    "postcss-load-config": "^3.1.0",
    "svelte": "^3.42.6",
    "svelte-check": "^2.2.6",
    "svelte-jester": "^2.1.3",
    "svelte-navigator": "^3.1.5",
    "svelte-preprocess": "^4.9.4",
    "tailwindcss": "^2.2.15",
    "ts-jest": "^27.0.5",
    "ts-node": "^10.2.1",
    "tslib": "^2.3.1",
    "typescript": "^4.4.3",
    "vite": "^2.5.10"
  }

[schicks]

I'm also getting that issue. When I look in the svelte-jester folder in node modules it appears that the preprocess file is missing; there's just a transformer.cjs and a transformer.mjs file in the dist directory. Is it possible that something went wrong in the build process when publishing v2.1.3?

[sebastianrothe]

Yeah, sorry about that. Will be fixed, see #81