Reading into existing instance uses creator property setup instead of mutator (setter, field)

[odrotbohm]

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Describe the bug

When reading into an existing object, the JsonMapper uses the deserializer of the creator property instead of the parameter of the accessor.

package example.three;

import static org.assertj.core.api.Assertions.*;

import tools.jackson.databind.json.JsonMapper;

import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collection;
import java.util.stream.Stream;

import org.junit.jupiter.api.DynamicTest;
import org.junit.jupiter.api.Test;
import org.junit.jupiter.api.TestFactory;

import com.fasterxml.jackson.annotation.JsonCreator;
import com.fasterxml.jackson.annotation.JsonProperty;
import com.fasterxml.jackson.annotation.JsonUnwrapped;

class Jackson3Test {

  @Test
  void readsIntoCreator() throws Exception {

    var mapper = JsonMapper.builder()
        .build();

    mapper.readerForUpdating(new ArrayListHolder("A")).readValue("""
        {
          "values" : [ "A", "B" ]
        }
        """);
  }

  public static class ArrayListHolder {
    Collection<String> values;

    ArrayListHolder(String... values) {
      this.values = new ArrayList<>(Arrays.asList(values));
    }

    public void setValues(Collection<String> values) {
      this.values = values;
    }
  }
}

Stack trace:

tools.jackson.databind.DatabindException: Cannot cast [Ljava.lang.String; to java.util.Collection
 at [Source: REDACTED (`StreamReadFeature.INCLUDE_SOURCE_IN_LOCATION` disabled); byte offset: #UNKNOWN] (through reference chain: example.three.Jackson3Test$ArrayListHolder["values"])
	at tools.jackson.databind.DatabindException.wrapWithPath(DatabindException.java:111)
	at tools.jackson.databind.deser.bean.BeanDeserializerBase.wrapAndThrow(BeanDeserializerBase.java:1850)
	at tools.jackson.databind.deser.bean.BeanDeserializer.deserialize(BeanDeserializer.java:288)
	at tools.jackson.databind.deser.DeserializationContextExt.readRootValue(DeserializationContextExt.java:267)
	at tools.jackson.databind.ObjectReader._bindAndClose(ObjectReader.java:1702)
	at tools.jackson.databind.ObjectReader.readValue(ObjectReader.java:1220)
	at example.three.Jackson3Test.readsIntoCreator(Jackson3Test.java:102)
	at java.base/java.lang.reflect.Method.invoke(Method.java:580)
	at java.base/java.util.ArrayList.forEach(ArrayList.java:1596)
	at java.base/java.util.ArrayList.forEach(ArrayList.java:1596)
Caused by: java.lang.ClassCastException: Cannot cast [Ljava.lang.String; to java.util.Collection
	at java.base/java.lang.Class.cast(Class.java:4067)
	at tools.jackson.databind.deser.impl.MethodProperty.set(MethodProperty.java:179)
	at tools.jackson.databind.deser.CreatorProperty.deserializeAndSet(CreatorProperty.java:219)
	at tools.jackson.databind.deser.bean.BeanDeserializer.deserialize(BeanDeserializer.java:286)
	... 7 more

Works on Jackson 2.

Version Information

3.0 RC8

Reproduction

No response

Expected behavior

No response

Additional context

No response

[cowtowncoder]

Thank you for reporting this.

I would expect this to fail for 2.x too, but will mark as 3.x as per report.

[JooHyukKim]

Wrote #5286 to verify indeed it did not work since 2.18.
Few questions tho, @cowtowncoder

1. this should work without annotating Collection<String> values; with @JsonMerge?
2. Also, when working, should it be MergingSettableBeanProperty that takes care of handling?

Then I can go take a look deeper

[cowtowncoder]

Ahhh. Reading exception more carefully, realized the problem is with type being used taken as String[] (from String ... for Creator property) while calling (correctly) Setter method (which takes Collection<String>).

This may be tricky to tackle.

In the meantime I would suggest a work-around of either:

1. Changing one of signatures so they'd match OR
2. Adding @JsonIgnore on Constructor to avoid it being detected