Creating Empathetic User Experiences with Next 12 and SWC: A Guide to Harnessing import.meta.url

Question

Creating Empathetic User Experiences with Next 12 and SWC: A Guide to Harnessing import.meta.url

In my Next.js 12 App with the Rust Compiler, I am utilizing Jest and WebWorkers. In one of my files, I am using import.meta.url. to create the worker.

The issue arises when Jest throws an error, stating that import.meta.url cannot be used outside of an ES Module due to transforming TypeScript code to CommonJs format. I came across a solution involving a Babel plugin that can transform these specific files containing import.meta.url. More details can be found here: https://github.com/facebook/jest/issues/12183#issuecomment-1004320665

However, I am hesitant to use Babel as my Jest configuration is based on Next's setup with the Rust compiler. It is unclear whether I can incorporate this babel plugin into my current configuration.

I am aware that another approach could be configuring Jest to use ESModules instead. However, I am reluctant to go down this path as it is still experimental and has caused some unexpected errors in my project.
Therefore, my question is: Is there a way (or perhaps a SWC plugin) to achieve this transformation using SWC?

typescript jestjs next.js web-worker swc-compiler

Answer 1

Answer №1

An efficient solution that avoids making extensive changes to the application or testing setup involves refactoring the import.meta.url call into a separate helper module. During testing of the original file, you can then mock the helper module as needed. Here's a high-level overview.

// my-module.js
import { importMetaUrl } from './import-meta-url'
export function foo() {
   return importMetaUrl()
}

// import-meta-url.js
export function importMetaUrl() {
  return import.meta.url
}

// my-module.test.js
import { foo } from './my-module'

jest.mock('./import-meta-url', () => ({
   importMetaUrl: () => 'http://www.example.org'
})

test('test', () => {
  expect(foo()).toEqual('http://www.example.org')
})

Answer 2

An efficient solution that avoids making extensive changes to the application or testing setup involves refactoring the import.meta.url call into a separate helper module. During testing of the original file, you can then mock the helper module as needed. Here's a high-level overview.

// my-module.js
import { importMetaUrl } from './import-meta-url'
export function foo() {
   return importMetaUrl()
}

// import-meta-url.js
export function importMetaUrl() {
  return import.meta.url
}

// my-module.test.js
import { foo } from './my-module'

jest.mock('./import-meta-url', () => ({
   importMetaUrl: () => 'http://www.example.org'
})

test('test', () => {
  expect(foo()).toEqual('http://www.example.org')
})

Creating Empathetic User Experiences with Next 12 and SWC: A Guide to Harnessing import.meta.url

Answer №1

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