When using the directions API like so:

builder = (...)
MapboxDirections client = builder.build();
 client.enqueueCall(new Callback<DirectionsResponse>() {
                @Override
                public void onResponse(@NonNull Call<DirectionsResponse> call, @NonNull Response<DirectionsResponse> response) {
                    (...)
                }

                @Override
                public void onFailure(@NonNull Call<DirectionsResponse> call, @NonNull Throwable throwable) {
                    (...)
                }
            });

if no route can be found, then onResponse will be called twice.

This is highly surprising/unexpected, and in our case, caused a crash.

Expected Behavior

This should be called only once.

Current Behavior

It is called twice.

Possible Solution

a return should be added right after this line:
https://github.com/mapbox/mapbox-java/blob/master/services-directions/src/main/java/com/mapbox/api/directions/v5/MapboxDirections.java#L161

Steps to Reproduce

A call should be made that results in a NoRoute response (for instance, 2.308538,48.852698 to 120.960515,23.69781).
See above.

Context (Environment)

In our case this produced a crash because we use an Rx SingleEmitter and onError must not be called twice.

Detailed Description

See "possible solution" above.

Possible Implementation

See "possible solution" above.