packages/karma-esm/src/middleware.js
function getCode(filePath) {
  // take code from cache if available
  const cachedCode = esm.compiler.getCached(filePath);
  if (cachedCode) {
    return cachedCode;
  }

  if (!fs.existsSync(filePath)) {
    throw new Error(`File does not exist: ${filePath}`);
  }

  // otherwise read code from file and compile it
  const code = fs.readFileSync(filePath, 'utf-8');
  return esm.compiler.compile(filePath, code);
}
function getCode(filePath) {
  // take code from cache if available
  const cachedCode = esm.compiler.getCached(filePath);
  if (cachedCode) {
    return cachedCode;
  }

  if (!fs.existsSync(filePath)) {
    throw new Error(`File does not exist: ${filePath}`);
  }

  // otherwise read code from file and compile it
  const code = fs.readFileSync(filePath, 'utf-8');
  return esm.compiler.compile(filePath, code);
}
Middleware for serving es modules. Karma doesn't serve any files not specified
beforehand. This is extremely inconvenient when working with es modules, as many
files are requested on the fly.