Imports broken in babel-jest when using babel and @babel/typescript

Do you want to request a feature or report a bug? Bug

What is the current behavior? It appears that Jest doesn’t play nice with TypeScript that’s compiled exclusively via Babel – e.g. without tsc.

If the current behavior is a bug, please provide the steps to reproduce and either a repl.it demo through https://repl.it/languages/jest or a minimal repository on GitHub that we can yarn install and yarn test.

I’ve got a minimal repro here: https://github.com/japhar81/JestRepro

#3202 indicates that the issue is with {"modules":false}. Indeed, yarn test with that setting yields an error; SyntaxError: Unexpected token import. Removing that setting (as in the repro code), yields a different error TypeError: (0 , express) is not a function.

Digging further lead me to this issue: https://github.com/Microsoft/TypeScript/issues/5458 – and I can confirm that if I change my import to be import express from 'express', things work, though of course TypeScript is angry as there’s no real default export in the express definition.

https://github.com/facebook/jest/issues/3202#issuecomment-318260688 references using

"plugins": [
        "transform-es2015-modules-commonjs",
        "dynamic-import-node"
      ]

Adding those in this same repo has no effect. The error remains TypeError: express is not a function. It’s possible these are no longer valid for Babel 7 and different plugins should be used – I’ve had no luck identifying if that’s the case.

What is the expected behavior? There should be some way to keep TypeScript happy with import * as express from 'express' and still have Jest operate. As yarn start demonstrates in this sample, it does compile and work with {"modules":false} in webpack. I’m not entirely sure where the difference is, but presumably if Webpack can do it, Jest can as well.

Please provide your exact Jest configuration and mention your Jest, node, yarn/npm version and operating system. Mac OS X 10.13.3 Yarn: 1.3.2 npm: 5.6.0 node: 9.3.0 Jest: 22.2.2 See Repo for Config

[casey-speer]

It appears that jest won’t look for typescript files to compile with babel by default, so in addition to any other typescript-related config in jest, I had to add

"transform": {
    "^.+\\.ts$": "babel-jest"
}

to my jest config in package.json.

Also, I had to npm install @babel/core babel-core@7.0.0-bridge.0 to get it working with babel 7 (needed for babel transpilation of typescript).

[AndrewSouthpaw]

yarn --check-files notes an incorrect peer dependency between babel-jest and babel-core…

yarn install v1.0.2
[1/4] 🔍  Resolving packages...
[2/4] 🚚  Fetching packages...
[3/4] 🔗  Linking dependencies...
warning "ajv-keywords@2.1.1" has incorrect peer dependency "ajv@^5.0.0".
warning "ajv-keywords@1.2.0" has incorrect peer dependency "ajv@>=4.9.0".
warning "babel-jest@22.2.2" has incorrect peer dependency "babel-core@^6.0.0 || ^7.0.0-0".
warning "request-promise-native@1.0.5" has incorrect peer dependency "request@^2.34".
warning "request-promise-core@1.1.1" has incorrect peer dependency "request@^2.34".

Otherwise it’s fine. I’ve tried doing a fresh install of node_modules multiple times now. 😕 Any other ideas?