AngularFirePerformance incompatible with Jest

[spicemix]

If I import AngularFirePerformance anywhere reachable by my Jest unit tests (part of @nrwl/nx) I get

TypeError: window.performance.mark is not a function

The error is right on the import, no additional code needed.

The likelihood is this is an incompatibility with Jest's performance-related code. Trying to copy over values from perf_hooks didn't work although it changed the error reports. I am opening the issue here to see if anyone has ideas how to fix this. I am using the latest stable versions of everything.

[google-oss-bot]

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[spicemix]

Line 61 of performance.ts looks like it may be the culprit: it's assumed here that if you have window.performance you will also have mark, but it seems Jest strips out the mark function. So checking that mark is also there on line 56 might fix the issue although it might prevent the code from being run in a Jest test. Of course I don't need AngularFirePerformance on my Jest runs, but I did want to work with the emulators rather than mocking out all of firebase for those tests. I'm not sure I could mock that function out before the error is thrown as a means of preventing it without modifying this code.

const trace$ = (traceId: string) => {
  if (typeof window !== 'undefined' && window.performance) {
    const entries = window.performance.getEntriesByName(traceId, 'measure') || [];
    const startMarkName = `_${traceId}Start[${entries.length}]`;
    const endMarkName = `_${traceId}End[${entries.length}]`;
    return new Observable<void>(emitter => {
      window.performance.mark(startMarkName);
      emitter.next();
      return {
        unsubscribe: () => {
          window.performance.mark(endMarkName);
          window.performance.measure(traceId, startMarkName, endMarkName);
        }
      };
    });
  } else {
    return EMPTY;
  }
};

[stephen-wigginton]

as a work around, adding the following to your jest.ts will fix it as well:

Object.defineProperty(window.performance, 'mark', {
  value: () => mock()
});```

[jamesdaniels]

Will be addressed in next patch