Make behaviour of @DefaultImplementation consistent

[graemerocher]

The @DefaultImplementation annotation is currently confusing since it doesn't influence bean selection but only the result of @Replaces. This PR makes it so that the annotation can also be used to control bean selection which makes it more logical and less confusing.

[sdelamo]

I think this change is a good idea but we should document this in the "Default Implementation" section of the docs. We should mention that @primary still has precedence over @DefaultImplementation

[sonarcloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
93.8% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarCloud

[dstepanov]

Personally, I don't like the idea of @DefaultImplementation defined on the interface, considering this can be implemented with priority.

I think this will not work correctly in a case class SomeImpl{X,Y, Z} extends SomeBase; abstract class SomeBase implements ISomeWithDefault and injecting SomeBase. The correct way would be to use some annotation processing to map the class name on which the annotation is applied to @DefaultImplementation and check if the inject point is trying to resolve that class.

[graemerocher]

right, I added this because the current implementation is confusing and because Guice supports this concept https://github.com/google/guice/blob/2b37f020862e45be58f246a63c2f97fdaff0d433/core/test/com/google/inject/ImplicitBindingTest.java#L54

The example you mention should work fine, we just need to make sure the implementing type matches the type to be injected.

If we don't agree to this change then I can maybe implement is some other way in the Guice bridge, but I would then suggest we deprecate @DefaultImplementation all together because the only place it is used is with @Replaces and the name and behaviour are very misleading

[dstepanov]

I'm OK with this. Does it work to not have any scope defined on the implementation like it's in the JavaDoc of DefaultImplementation?

[graemerocher]

yes it does