Automated onError() message generation

File.java

public static Action1<Throwable> crashOnError() {
    final Throwable checkpoint = new Throwable();
    return throwable -> {
        StackTraceElement[] stackTrace = checkpoint.getStackTrace();
        StackTraceElement element = stackTrace[1]; // First element after `crashOnError()`
        String msg = String.format("onError() crash from subscribe() in %s.%s(%s:%s)",
            element.getClassName(),
            element.getMethodName(),
            element.getFileName(),
            element.getLineNumber());

        throw new OnErrorNotImplementedException(msg, throwable);
    };
}

I thought about doing something like this but balked because you would have the pay the performance penalty of building the stack trace every time you call the method even if an error isn't emitted. I guess you think the debugability is worth the performance penalty?

Timber uses the same technique to determine the logging tag and I'm using it all over the place. (In fact, Timber is the inspiration for how this works.) If I'm alright with that, then I definitely am alright with this.