nx/packages/jest/plugins/resolver.ts

import { dirname, extname } from 'path';
import type defaultResolver from 'jest-resolve/build/defaultResolver';

interface ResolveOptions {
  rootDir: string;
  basedir: string;
  paths: string[];
  moduleDirectory: string[];
  browser: boolean;
  extensions: string[];
  defaultResolver: typeof defaultResolver;
}

let compilerSetup;
let ts;

function getCompilerSetup(rootDir: string) {
  const tsConfigPath =
    ts.findConfigFile(rootDir, ts.sys.fileExists, 'tsconfig.spec.json') ||
    ts.findConfigFile(rootDir, ts.sys.fileExists, 'tsconfig.test.json') ||
    ts.findConfigFile(rootDir, ts.sys.fileExists, 'tsconfig.jest.json');

  if (!tsConfigPath) {
    console.error(
      `Cannot locate a tsconfig.spec.json. Please create one at ${rootDir}/tsconfig.spec.json`
    );
  }

  const readResult = ts.readConfigFile(tsConfigPath, ts.sys.readFile);
  const config = ts.parseJsonConfigFileContent(
    readResult.config,
    ts.sys,
    dirname(tsConfigPath)
  );
  const compilerOptions = config.options;
  const host = ts.createCompilerHost(compilerOptions, true);
  return { compilerOptions, host };
}

module.exports = function (path: string, options: ResolveOptions) {
  const ext = extname(path);
  if (
    ext === '.css' ||
    ext === '.scss' ||
    ext === '.sass' ||
    ext === '.less' ||
    ext === '.styl'
  ) {
    return require.resolve('identity-obj-proxy');
  }
  // Try to use the defaultResolver
  try {
    return options.defaultResolver(path, {
      ...options,
      packageFilter: (pkg) => ({
        ...pkg,
        main: pkg.main || pkg.es2015 || pkg.module,
      }),
    });
  } catch (e) {
    if (
      path === 'jest-sequencer-@jest/test-sequencer' ||
      path === '@jest/test-sequencer'
    ) {
      return;
    }
    // Fallback to using typescript
    ts = ts || require('typescript');
    compilerSetup = compilerSetup || getCompilerSetup(options.rootDir);
    const { compilerOptions, host } = compilerSetup;
    return ts.resolveModuleName(path, options.basedir, compilerOptions, host)
      .resolvedModule.resolvedFileName;
  }
};