Issue

I’m playing around with migrating a package to Vue 3 and upgraded a couple of its dependencies including vue-jest to v5.0.0-alpha.5. When running a small test for a JavaScript file which is importing a Vue single file component, I receive the following error from vue-jest:

ERROR: Unable to load the module "typescript". Using "ts-jest" requires this package to be installed.

Running coverage on untested files...Failed to collect coverage from /home/phil/dev/packages/vue-accessible-color-picker/src/ColorPicker.vue
ERROR: Unable to load the module "typescript". Using "ts-jest" requires this package to be installed. To fix it:
    ↳ install "typescript": `npm i -D typescript` (or `yarn add --dev typescript`)
STACK: Error: Unable to load the module "typescript". Using "ts-jest" requires this package to be installed. To fix it:
    ↳ install "typescript": `npm i -D typescript` (or `yarn add --dev typescript`)
    at Importer._import (/home/phil/dev/packages/vue-accessible-color-picker/node_modules/ts-jest/dist/util/importer.js:143:15)
    at Importer.typescript (/home/phil/dev/packages/vue-accessible-color-picker/node_modules/ts-jest/dist/util/importer.js:74:21)
    at ConfigSet.get (/home/phil/dev/packages/vue-accessible-color-picker/node_modules/ts-jest/dist/config/config-set.js:384:40)
    at ConfigSet.compilerModule (/home/phil/dev/packages/vue-accessible-color-picker/node_modules/ts-jest/dist/util/memoize.js:43:24)
    at ConfigSet.readTsConfig (/home/phil/dev/packages/vue-accessible-color-picker/node_modules/ts-jest/dist/config/config-set.js:625:23)
    at ConfigSet.get (/home/phil/dev/packages/vue-accessible-color-picker/node_modules/ts-jest/dist/config/config-set.js:313:31)
    at ConfigSet._typescript (/home/phil/dev/packages/vue-accessible-color-picker/node_modules/ts-jest/dist/util/memoize.js:43:24)
    at ConfigSet.get [as typescript] (/home/phil/dev/packages/vue-accessible-color-picker/node_modules/ts-jest/dist/config/config-set.js:283:25)
    at getTsJestConfig (/home/phil/dev/packages/vue-accessible-color-picker/node_modules/vue-jest/lib/utils.js:71:30)
    at processTemplate (/home/phil/dev/packages/vue-accessible-color-picker/node_modules/vue-jest/lib/process.js:72:20)

It seems that some part of the code is requiring the ts-jest package which I don’t have installed because my package is not using TypeScript. It seems that some part of the code is requiring the typescript via the ts-jest package which is installed as part of the vue-jest package. However, my project doesn’t use TypeScript at all. I suspect the issue starts happening in https://github.com/vuejs/vue-jest/blob/next/lib/process.js (in particular around https://github.com/vuejs/vue-jest/blob/next/lib/process.js#L63-L72). Logging { tsconfig } after the line containing const tsconfig = getTsJestConfig(config) does not log anything. The utils function for retrieving the jest configuration for TypeScript in https://github.com/vuejs/vue-jest/blob/next/lib/utils.js#L69 seems to be returning a configSet variable missing the properties that being used on the next line.

Reproduction

(This isn’t exactly a minimal reproduction case, but I believe the issue is largely independent from how my package is structured or written.)

1. Clone package.

   git clone https://github.com/kleinfreund/vue-accessible-color-picker.git
   

2. Enter package.

   cd vue-accessible-color-picker
   

3. Check out migrate-to-vue-version-3 branch.

   git checkout migrate-to-vue-version-3
   

4. Install dependencies

   npm install
   

5. Run the test for the index.js file.

   npm test -- ./src/index.test.js
   

6. (Optional) Install typescript and re-run the test in step 5 to see the issue fixed.

   npm install --save-dev typescript
   

Notes

• Related pull request removing a depenency on the typescript package: Gate typescript behind tsconfig check and added e2e test for project that doesn't use Typescript (Fix #282) #283
• After installing TypeScript (using npm install --save-dev typescript) and replacing import Vue from 'vue' with import * as Vue from 'vue' (for some reason, Vue evaluates to undefined otherwise), the script npm test -- ./src/index.test.js passes with expected warnings.
• After disabling the coverage settings in the jest.config.js file (i.e. removing collectCoverage and collectCoverageFrom settings), the script npm test -- ./src/index.test.js passes with expected warnings.