edge-cases.md

Notable edge-cases

Calling watchPosition with the timeout option

Browsers differ greatly in how they handle watchPosition calls when the timeout option is set. From some quick initial testing:

• With a timeout of 0:
  • Chrome (macOS/Android) will:
    • Immediately call the error callback with a timeout error
    • At some later point, call the success callback with a position
    • Continue to call both the success and error callbacks over time in an inscrutable order
  • Firefox (macOS) will:
    • Never call the error callback
    • Call the success callback with positions over time
  • Safari (macOS/iOS) will:
    • Immediately call the error callback with a timeout error
    • Never call the success callback
• With a timeout of 1 (basically, impossibly low but not zero):
  • Safari (macOS/iOS) will:
    • Immediately call the error callback with a timeout error
    • At some later point, call the success callback with a position
    • Continue to call the success callback over time
  • Other browsers will behave basically the same as with a timeout of 0

For now, fake-geolocation will not attempt to emulate this behavior. It will instead do what it seems like the spec intends: call the error callback every time the timeout is reached, but do not stop watching for positions just because acquiring the position timed out previously.

Revoking and re-granting permissions while watchPosition is active

Browsers differ greatly in how they handle revoked/re-granted permissions during watchPosition calls. From some quick initial testing, while in the middle of an active watchPosition call, revoking permissions will:

• Chrome (macOS) will:
  • Immediately call the error callback with a position unavailable error, followed by a permission denied error
  • Never call the success callback again after re-granting permissions
• Firefox (macOS) will:
  • Not call the error callback
  • Resume calling the success callback with positions after re-granting permissions
• Safari (macOS) will:
  • Not call the error callback
  • Never call the success callback again after re-granting permissions