Compile-time issues when upgrading to 4.1.2

[ssynix]

Description

I'm trying to upgrade java-client 3.4.1 to 4.1.2.

Details

Our framework is built on top of Selenium and Appium's java-client. With the recent update, a simplified version of our interfaces below is failing to compile. I've tried multiple modifications to our code with no result, especially since I don't understand why the error is happening.

Code To Reproduce Issue

I've managed to narrow down the problem to this set of interfaces on Ideone. I believe this change is what is causing the issue for us.

• For some reason, if we continue to extend MobileDriver without a generic parameter, the compiler is not able to override execute. This completely baffles me...
• If I extend MobileDriver<WebElement> or change all our interfaces to generic (IFrameworkMobileDriver<T extends WebElement> extends MobileDriver<T>), the Java compiler pulls two versions of FindsByXPath into the our class with what it thinks are non-covariant return types (List<T> and List<WebElement> are not covariant?).

Any idea what I'm missing here?

[TikhomirovSergey]

Hi @ssynix
It is known issue. There are many details provided here #413
Also there are many details how to resolve it. You need to use eclipse compiler.
If you use maven then https://github.com/appium/java-client/blob/master/archive/pom.xml#L217
if you use gradle then https://github.com/appium/java-client/blob/master/build.gradle#L31
I'm waiting for your response.

[ssynix]

It seems I haven't been as thorough in my searching! Unfortunately, the current set up at our company gets in the way of using a different compiler.

I read most of the issues that you linked, and I see there have been a lot of development going on into refactoring these interfaces, but I still fail to understand why this issue is happening. Are we facing a bug in the java compiler?

I managed to fix the problem by changing our override from
public void execute(String driverCommand, Map<String, ?> parameters) {}
to
public void execute(String driverCommand, Map parameters) {}

I still have no idea why making MobileDriver generic would suddenly necessitate removing the type parameters from our overridden methods.

I have given up on trying to understand this issue for now and will probably resort to the fix/workaround above.

Thanks for the additional details!

[TikhomirovSergey]

@ssynix Yes. It is probably javac issue. But I'm not sure.