Fixes #4584: add AnnotationIntrospector method for default Creator discovery (findDefaultCreator())

[cowtowncoder]

Implements #4584.

[cowtowncoder]

Implementation by other modules would be along lines of (see PrimaryCreatorDetection4584Test for bigger examples):

public class PrimaryDetectingIntrospector extends AnnotationIntrospector
{
        @Override
        public PotentialCreator findDefaultCreator(MapperConfig<?> config,
                AnnotatedClass valueClass,
                List<PotentialCreator> declaredConstructors,
                List<PotentialCreator> declaredFactories)
        {
           if (valueClass.getRawType() == MyClass.class) {
              // Only detect constructors (for example)
              for (PotentialCreator ctor : declaredConstructors) {
                  // use whatever logic to see if this should match (annotations, types etc)
                if (ctor.paramCount() == 1) {
                    // important: indicate mode (DELEGATING or PROPERTIES)
                   // (strictly speaking only required for 1-param case but good practice):
                   ctor.overrideMode(JsonCreator.Mode.PROPERTIES);
                   return ctor;
                }
              }
           }
           return null;
        }
}

[cowtowncoder]

@JooHyukKim @k163377 Here's complete implementation for review; will merge soon.

[JooHyukKim]

@JooHyukKim @k163377 Here's complete implementation for review; will merge soon.

I will try to review today 👍🏼

[cowtowncoder]

@JooHyukKim Sounds good - I think I'll merge this and address anything you may find with a follow-up. This so I can merge to master tonight.

[JooHyukKim]

@JooHyukKim Sounds good - I think I'll merge this and address anything you may find with a follow-up. This so I can merge to master tonight.

Makes sense, I've been watching this PR for a couple of days and LGTM so far.
I will probably leave a few comments around JavaDoc.

[JooHyukKim]

   /**
     * Method called to detect so-called <b>Primary Creator</b> (via {@link #findCreatorAnnotation}).
     * Primary Creator is the Creator to select for use when no explicit annotation is found.
     * .... // rest omitted

@cowtowncoder I was thinking maybe the first part of the JavaDoc could be this. But other than that, seems good.

[cowtowncoder]

Hmmm. Reference to findCreatorAnnotation() seems misplaced since potential creators includes all constructors, most applicable static factory methods, not just ones annotated.
(in fact, the main point is to allow selecting non-annotated creators).

[k163377]

I am not familiar with English, but is the name of this method Primary OK?
Personally, it seemed like a function to get a creator with a higher priority than the setting by annotation such as JsonCreator.
How about a name like findImplicitCreator?

[cowtowncoder]

It's up to debate, I'm sure -- at first I was considering canonical.
But I see the challenge wrt precedence.
Instead of implicit (which is used as sort of fallback already, which is why I hesitate with it), we could consider "default"?

findDefaultCreator()? (and similar naming)

[k163377]

findDefaultCreator

I can think of findFallbackConstructor, but findDefaultCreator would also be good.

[cowtowncoder]

Ok I'll go with "default" since that to me conveys it better. But as long as descriptions define logic either would work.
(note: cannot use "constructor" since method can return constructor OR factory method (hence, creator to cover both types))
Thank you @k163377 !

[cowtowncoder]

Ok, tweaked a bit: lmk for further suggestions.

[k163377]

@cowtowncoder
Deployment failing?
I tried to reflect it in kotlin-module, but the name was still findPrimary....
https://github.com/FasterXML/jackson-databind/actions/runs/9884061392

[JooHyukKim]

Could be just temporary error. It might simply succeed by re-running.
@cowtowncoder Could you try re-running above build?

[cowtowncoder]

@k163377 @JooHyukKim There is something odd about CI, seems to fail the first snapshot deployment for merged PRs. No idea why. Same does not occur for merges from earlier branches I think (and PRs will not try to deploy so won't fail there). Something to do with access, I suppose, but these are branches I create and merge and my credentials should be sufficient.

I re-ran it, and as usual that succeeds. Need to keep an eye on this going forward but not sure how to resolve it.

[cowtowncoder]

@k163377 Should work better now

[k163377]

I submitted a problem I found when implementing to kotlin-module.
#4620