geolocation.watchPosition passes errors to the success function

[gnesher]

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[x] bug report
[ ] feature request
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Current behavior:
Using geolocation.watchPosition when (for example) user refuses to provide access to the device location will provide the following error object in the subscription (without throwing an error)

GeolocationPositionError {code: 2, message: "application does not have sufficient geolocation permissions."}code: 2message: "application does not have sufficient geolocation permissions."proto: GeolocationPositionError

The return value is defined as Geoposition (interface) and doesn't allow me to a GeolocationPositionError object.

Expected behavior:
The expected behavior would be to throw the error and close the subscription

Steps to reproduce:
start listening to the geolocation of the device without approving access to the device location

Other information:

Tested only on Android devices

Ionic info: (run ionic info from a terminal/cmd prompt and paste output below):

Ionic:

ionic (Ionic CLI) : 4.12.0 (C:\Users\gnesher\AppData\Roaming\npm\node_modules\ionic)
Ionic Framework : @ionic/angular 4.11.7
@angular-devkit/build-angular : 0.803.23
@angular-devkit/schematics : 8.2.2
@angular/cli : 8.2.2
@ionic/angular-toolkit : 2.0.0

Cordova:

cordova (Cordova CLI) : 8.1.2 (cordova-lib@8.1.1)
Cordova Platforms : android 7.1.4
Cordova Plugins : cordova-plugin-ionic-keyboard 2.2.0, cordova-plugin-ionic-webview 4.1.3, (and 15 other plugins)

System:

Android SDK Tools : 26.1.1 (C:\Android\android-sdk)
NodeJS : v12.14.1 (C:\Program Files\nodejs\node.exe)
npm : 6.13.4
OS : Windows 10

[DavidWiesner]

I agree this is a weird behavior. In the specs of (watchPosition)[https://w3c.github.io/geolocation-api/#dfn-watch-process] you can see multiple errors can be fired before a new position will be sended. Observables instead can only handle one Error and will be closed after the first error. Maybe that's the reason the ionic team decide to ship both value to the next callback.

But this behavior should be at least also be expressed in the types. Therefore the return type of watchPostion should be changed to Observable<Geoposition|GeolocationPositionError>

[DavidWiesner]

Sorry i mixed up Observable and Subject. So you are right. The Error should be delivered via the error callback of the Observable

[DavidWiesner]

Sorry my fault I read the Rxjs context about Observables (http://reactivex.io/documentation/contract.html) again. An Observable can only emit on error. But as stated in the w3c Geolocation API Specification an error can be occur multiple times (see https://w3c.github.io/geolocation-api/#dfn-watch-process) e.g.: a timeout. I reopen the pullrequest to adjust the types that will be delivered by the Observable. That will make it more clear waht you can expect.