Router: Why does HashLocationStrategy listen to popState and hashChange events?

[matanlurey]

Steps to reproduce and a minimal demo of the problem

View hash_location_strategy:

  void onPopState(UrlChangeListener fn) {
    this._platformLocation.onPopState(fn);
    this._platformLocation.onHashChange(fn);
  }

Internal clients rely on manually dispatching window.hashchange events in order to have other libraries that rely on listening to hashchange manually know what the route is. Unfortunately, this seems to cause duplicate routing now.

A workaround is to override HashLocationStrategy and replace:

@override
  void onPopState(UrlChangeListener fn) {
    // Instead of listening to hashChange + popState, just listen to hashChange.
    //
    // We manually invoke hashChange events which can cause duplicate routing.
    _platformLocation.onPopState(fn);
  }

I'd prefer not to keep it like that long-term.

Current behavior

Listens to both type of events.

Expected/desired behavior

I'd imagine listen to just one?

[vsavkin]

Closed here #10011

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