[TS 3.8] Jest is unable to work with "type-only imports/exports"

🐛 Bug Report

When using a new “type-only impors/exports” feature introduced in TypeScript 3.8 it is impossible to run tests due to the parsing error:

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

    Jest encountered an unexpected token

    This usually means that you are trying to import a file which Jest cannot parse, e.g. it's not plain JavaScript.

    By default, if Jest sees a Babel config, it will use that to transform your files, ignoring "node_modules".

    Here's what you can do:
     • To have some of your "node_modules" files transformed, you can specify a custom "transformIgnorePatterns" in your config.
     • If you need a custom transformation specify a "transform" option in your config.
     • If you simply want to mock your non-JS modules (e.g. binary assets) you can stub them out with the "moduleNameMapper" config option.

    You'll find more details and examples of these config options in the docs:
    https://jestjs.io/docs/en/configuration.html

    Details:

    SyntaxError: /jest-ts-type-only-export-import-repro/src/test.ts: Unexpected token (3:12)

      1 | import { a } from './exporter';
      2 | 
    > 3 | import type { Foo } from './exporter';
        |             ^
      4 | 
      5 | test("it should parse", () => {
      6 |     const q: Foo = { a };

      at Object.raise (node_modules/@babel/parser/src/parser/location.js:41:63)
      at Object.unexpected (node_modules/@babel/parser/src/parser/util.js:150:16)
      at Object.expectContextual (node_modules/@babel/parser/src/parser/util.js:94:41)
      at Object.parseImport (node_modules/@babel/parser/src/parser/statement.js:2038:12)
      at Object.parseImport (node_modules/@babel/parser/src/plugins/typescript/index.js:1826:20)
      at Object.parseStatementContent (node_modules/@babel/parser/src/parser/statement.js:248:25)
      at Object.parseStatementContent (node_modules/@babel/parser/src/plugins/typescript/index.js:1893:20)
      at Object.parseStatement (node_modules/@babel/parser/src/parser/statement.js:147:17)
      at Object.parseBlockOrModuleBlockBody (node_modules/@babel/parser/src/parser/statement.js:866:25)
      at Object.parseBlockBody (node_modules/@babel/parser/src/parser/statement.js:842:10)

To Reproduce

• use a type-only export/import in some file
• run test that imports (directly or indirectly) that file

Expected behavior

Jest should be able to parse type-only exports/imports and run tests without any problems.

Link to repl or repo (highly encouraged)

https://github.com/surgeboris/jest-ts-type-only-export-import-repro

envinfo

  System:
    OS: Linux 5.3 Ubuntu 19.10 (Eoan Ermine)
    CPU: (4) x64 Intel(R) Core(TM) i5-6200U CPU @ 2.30GHz
  Binaries:
    Node: 12.13.1 - ~/.npm-global/bin/node
    Yarn: 1.22.0 - ~/.npm-global/bin/yarn
    npm: 6.13.7 - ~/.npm-global/bin/npm
  npmPackages:
    jest: ^25.1.0 => 25.1.0 

[poltak]

Updating the main jest package also to v26.0.1, same as babel-jest, was what fixed it for me. The transform config now automatically points to to node_modules/babel-jest instead of node_modules/jest-config/node_modules/babel-jest.

Maybe that’s obvious, but putting it out there if not.

[jeysal]

See https://github.com/babel/babel/issues/10981