@firebase/performance needs some changes, to work as an ES module

[akauppi]

While other modules work with ES modules based browsers, @firebase/performance (0.900.17) needs some changes.

With ESM, one shouldn't do dynamic initialisation in the module body with classes that themselves are imported. The current code does this at places, causing errors like "Cannot access ErrorFactory before initialisation" to arise, at runtime.

Here are the places where I stabbed node_modules/@firebase/performance/dist/index.esm2017.js to get by them.

Note: Actual changes should be carefully though after by Firebase authors. I am merely listing the work-arounds. Preceding code is in the comments.

//const ERROR_FACTORY = new ErrorFactory(SERVICE, SERVICE_NAME, ERROR_DESCRIPTION_MAP);

const ERROR_FACTORY = {
  create(...args) {   // First time here. Replace ourselves (avoids calling 'new' at module load).
    const { create } = new ErrorFactory(SERVICE, SERVICE_NAME, ERROR_DESCRIPTION_MAP);
    ERROR_FACTORY.create = create;
    return create(...args);
  }
}

//const consoleLogger = new Logger(SERVICE_NAME);
//consoleLogger.logLevel = LogLevel.INFO;

let consoleLogger = {
  info: _consoleLoggerFirst('info')
};
function _consoleLoggerFirst(level) {
  return (...args) => {
    const logger = new Logger(SERVICE_NAME);
    logger.logLevel = LogLevel.INFO;

    consoleLogger= logger;
    logger[level](...args);
  }
}

//registerPerformance();
//registerVersion(name, version);

let registered;
function getPerformanceWrapper(...args) {
  if (!registered) {
    registerPerformance();
    registerVersion(name, version);
    registered = true;
  }
  return getPerformance(...args)
}
function initializePerformanceWrapper(...args) {
  if (!registered) {
    registerPerformance();
    registerVersion(name, version);
    registered = true;
  }
  return initializePerformance(...args)
}

//export { getPerformance, initializePerformance, trace };
export { getPerformanceWrapper as getPerformance, initializePerformanceWrapper as initializePerformance, trace };

Edit:

I complemented some of the snippets that had remain partial, and added a wrapper for initializePerformanceWrapper (shot myself in the foot by having changed to using it!).

[Feiyang1]

IIUC that can only happen if there is a circular dependency which is not the case for ErrorFactory which is imported from @firebase/util.

Did you actually encounter this error in your app?

[akauppi]

I did. The circular dependency maybe comes from that my code imports both @firebase/app and @firebase/performance. The latter imports @firebase/app, at least.

Hey, I have the repo here for you: https://github.com/akauppi/GroundLevel-firebase-es/tree/recamp-firebase-9x

packages/app-deploy-ops/src/main.js

[akauppi]

The problem remains in 0.900.19, where I get the following error without edits:

index.esm2017.js:77 Uncaught ReferenceError: Cannot access 's' before initialization

I understand this can be a particular use case and not a general concern.