[wozhenbang2004]

Fixes #6397.

An immutable builder can return a replacement instance from a setter. When the value is read before the creator is invoked, applying the buffered assignment currently drops that returned instance.

Carry the replacement forward for buffered regular properties on the builder path. Ordinary bean assignment and buffered any-setter, merge, and map entries keep their current behavior.

The regression covers array-shaped and object-shaped input and verifies that a mutable bean ignores a setter return value. The two immutable-builder cases fail on the unmodified implementation.

Maven clean verify on JDK 21 completed with 7,775 tests passed and 1 skipped after merging the current 3.x base.

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[cowtowncoder]

Something wrong with this pr... ?

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[cowtowncoder]

@wozhenbang2004 Could you please enable "Allow edits from maintainers" on this PR? I'd like to push a small update directly: 3.x is now 3.4.0-SNAPSHOT (3.3.0 was released), so the #6397 release note entry needs to move into a new 3.4.0 section (and [3.4.0] in CREDITS) after merging 3.x into this branch.

Thanks!

[cowtowncoder]

Suggestion for a small refactoring to avoid the instanceof check and cast in PropertyBasedCreator.build(): add assignAndReturn() to the base PropertyValue class with a default implementation, and override it in Regular:

// PropertyValue (base)
/**
 * Method called to assign stored value to given instance, returning the
 * instance to use from then on: for (immutable) Builders this may differ
 * from the one passed in. Default implementation calls {@link #assign} and
 * returns the original instance.
 *
 * @since 3.4
 */
public Object assignAndReturn(DeserializationContext ctxt, Object bean) throws JacksonException {
    assign(ctxt, bean);
    return bean;
}

// PropertyValue.Regular
@Override
public Object assignAndReturn(DeserializationContext ctxt, Object bean) throws JacksonException {
    return _property.setAndReturn(ctxt, bean, value);
}

and then in PropertyBasedCreator.build():

for (PropertyValue pv = buffer.buffered(); pv != null; pv = pv.next) {
    if (buffer._mayRebind) {
        bean = pv.assignAndReturn(ctxt, bean);
    } else {
        pv.assign(ctxt, bean);
    }
}

The _mayRebind check still needs to stay (as ignoresSetterReturnValueForOrdinaryBean verifies, a fluent setter on a regular bean must not replace the bean), but the branching is then on builder-vs-bean rather than on the concrete PropertyValue subtype. Behavior of Any, Map and AnyParameter is unchanged since they use the default.

[wozhenbang2004]

@cowtowncoder Maintainer edits are enabled now. Thanks for taking care of the update!

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[gitar-bot]

Code Review ✅ Approved

🟡 Medium risk · Applying setter-return replacements during buffered deserialization could produce incorrect final objects if a builder setter returns an unexpected instance.

Fixes buffered regular property assignment on immutable creator-based builders so the replacement instance returned by a setter is carried forward instead of being dropped when the value is read before the creator runs. No issues found.

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