Function withEnv

test/runtimePaths.test.js:289–294

(key, val, fn)

  // fixed path, not a version scan. Verified against volta-cli/volta
  // volta-layout v4 `package_image_dir` + package/manager.rs `source_dir`.
  function withEnv(key, val, fn) {
    const orig = process.env[key];
    if (val === undefined) delete process.env[key]; else process.env[key] = val;
    try { return fn(); }
    finally { if (orig === undefined) delete process.env[key]; else process.env[key] = orig; }
  }

  it('includes <VOLTA_HOME>/tools/image/packages/@evomap/evolver/lib/node_modules', () => {
    withEnv('VOLTA_HOME', path.join(os.tmpdir(), 'fake-volta'), () => {