Singleton *Plugins* don't resolve dependencies recurrently

[hinerm]

If you have a non-contextual object that you want to connect with other contextual objects, and thus try to Context.inject it, any @Parameters that are SingletonServices will NOT be created/injected. You will get a [ERROR] java.lang.IllegalArgumentException: Required service is missing.

If those singleton services are initialized beforehand, e.g. as an @Parameter or another contextual object that is used before injecting the non-contextual object, then the injection will proceed without errors.

[ctrueden]

Sorry, I don't understand the issue. Can you make an MCVE?

[hinerm]

@ctrueden I think I may have misunderstood the root cause here myself, but I am not sure if there are two separate issues or not.

The use case that brought up the issue is:

• I have a class with Contextual parameters
• In the constructor, I tried to pass a Context and call inject(this) to auto-pop the fields. But this would fail specifically on injecting the SingletonService parameters.

However, I have now noticed that there may be a more general error state:

• I have a singleton service
• One of the singleton plugins of that service has an @Parameter on legacy service
• If I try to load that plugin greedily (e.g. in the initialize method) it will emit an [ERROR] java.lang.IllegalArgumentException: Required service is missing: net.imagej.legacy.LegacyService. But if I do it lazily, everything is fine.

adjusting service priority didn't seem to matter. I don't know.. it needs more exploration. But there were times I resolved errors in my singleton plugin's initialization by adding a dependency to that plugin's required service, to my singleton service.

[hinerm]

yeah I just double-checked and it wasn't about injection but timing.. I can inject that FijiAssistantChat now, probably because I'm doing things not at initialization.

[hinerm]

Nope I was wrong. I was just confused about when the error appears. Since going back to manual context injection, I get [ERROR] java.lang.IllegalArgumentException: Required service is missing: sc.fiji.llm.chat.ContextItemService when starting the Fiji Chat... plugin.

I "fixed" it by adding an @Parameter on ContextItemService to the SwingChatbotService in this commit

[ctrueden]

The ContextItemService does not extend an appropriate marker interface (either SciJavaService or ImageJService), and so it won't be included in the SciJava Context upon creation under normal circumstances. How are you launching the program? From a main method? From a unit test? From Fiji itself? Regardless: either add the marker interface declaration, or else construct the SciJava Context to include all services on the classpath (new Context()).