Compiler manager should use providers

[cstamas]

To figure out presence of component,
and if construction fails, report some
sane(r) message tham obvious false
information: "compiler not present".

[cstamas]

Sisu in general is fully lazy: see https://eclipse.github.io/sisu.inject/apidocs/reference/org/eclipse/sisu/BeanEntry.html

The Provider<C> is JSR330 wrapper of that above, calling into BeanEntry#getProvider(). Presence of BeanEntry means "bean is registered" (i.e. via index). But, beans in Sisu are always lazily created (unless is eager singleton).

Doing Map<String, MyComponent>.get("akey") builds upon these, and in case of construction failure it "pretends" that bean is not present, returns null as per Map contract. Note that all the map values are lazy, created ONLY when you do Map.get

[laeubi]

Should that not mean that it is NOT there if it is null?

[cstamas]

yes, yes, bad worded comments but i hope the intent is clear 😄

[laeubi]

Maybe remove or move down into the if case (code speaks for itself?)

[kriegaex]

Superseded by #361. Thank you so much, @cstamas.