pnpm/__utils__/jest-config/jest.transform.js

import { Buffer } from 'node:buffer'
import { fileURLToPath } from 'node:url'
import { transformSync } from '@babel/core'
import { transformSync as stripTypes } from 'amaro'

// This file was created referencing:
// https://github.com/jestjs/jest/issues/15443

export default {
  process(sourceText, sourcePath) {
    // Node.js v26 removed the `transform` mode and `sourceMap` option from
    // `module.stripTypeScriptTypes`, so we call into `amaro` (the same
    // wasm-backed transformer Node.js uses internally) directly. `transform`
    // mode is required to keep inline source maps — without them, interactive
    // debuggers can't map type-stripped test files back to their on-disk
    // location. For background, see https://github.com/pnpm/pnpm/pull/11024.
    const { code: stripped, map } = stripTypes(sourceText, {
      mode: 'transform',
      sourceMap: true,
      filename: sourcePath,
    })
    const code = map
      ? `${stripped}\n//# sourceMappingURL=data:application/json;base64,${Buffer.from(map).toString('base64')}\n`
      : stripped

    // Using the presence of the DisposableStack global to feature detect
    // whether the current Node.js runtime supports explicit resource
    // management. If it exists, we don't need to do any more work.
    if (typeof DisposableStack !== 'undefined') {
      return { code }
    }

    // Node.js 24.0.0 introduces explicit resource management:
    // https://nodejs.org/en/blog/release/v24.0.0#v8-136
    //
    // When running tests on Node.js before version 24, we'll need to transpile
    // the "using" keyword. Otherwise Jest will fail to recognize this syntax
    // and show confusing errors when running some tests.
    //
    // This can be deleted when pnpm no longer needs to support Node.js v22.
    return babel(code, sourcePath)
  }
}

function babel (code, sourceFileName) {
  return transformSync(code, {
    babelrc: false,
    configFile: false,
    sourceFileName,
    plugins: [fileURLToPath(import.meta.resolve('@babel/plugin-transform-explicit-resource-management'))]
  })
}