I was trying to update a project, and didn't think of updating my dependency to STK. So I was starting this projects based on 4.5.1, with STK 1.4.4. At startup, this resulted in this exception

A binding to info.magnolia.cms.core.AggregationState was already configured at info.magnolia.objectfactory.guice.GuiceComponentConfigurationModule.bindImplementation(GuiceComponentConfigurationModule.java:157).

I traced it down to the GuiceComponentProviderBuilder.build() call in info.magnolia.cms.beans.config.ConfigLoader#load.

I'm reporting this as "critical", because it's easy to overlook one or the other dependency when upgrading a project, especially until we don't fix MAGNOLIA-3545

I'm not suggesting such a project should work or even start, but it would be nice if the exception message was a little less puzzling, or offered some sort of information or hint that would allow to track the problem down.

• a hint that there might be old/conflicting modules ? Perhaps warnings beforehand when loading those modules ? I didn't check, but I'm suspecting the conflict happens with a legacy module definition property ?
• for advanced users or developers, it would probably also be helpful to point at where the conflict comes from.

I'm also suspecting this sort of conflict could occur, say, if two modules try to register the same component (or using the same key) ?