NPE deserializing Recursive Structure When Ignoring Properties (same as #1755)

[hankolerd]

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Describe the bug

Disclaimer; This may be duplicate of #1755 - But thought I should raise separately in case root-cause is different, as that is raised against 2.9.

Starting with Jackson-Databind 2.12.0, attempting to deserialize a recursive data structure with a custom JacksonAnnotationIntrospector configured to ignore properties, for example:

new JacksonAnnotationIntrospector() {
   @Override
   public Value findPropertyIgnoralByName(MapperConfig<?> config, Annotated a) {
      return JsonIgnoreProperties.Value.forIgnoredProperties("CanBeAnyValue");
   }
}

A NullPointerException will be thrown during deserialization:

Caused by: java.lang.NullPointerException: Cannot invoke "com.fasterxml.jackson.databind.JsonDeserializer.getObjectIdReader()" because "valueDes" is null
	at com.fasterxml.jackson.databind.deser.std.CollectionDeserializer._deserializeFromArray(CollectionDeserializer.java:333)
	at com.fasterxml.jackson.databind.deser.std.CollectionDeserializer.deserialize(CollectionDeserializer.java:244)
	at com.fasterxml.jackson.databind.deser.std.CollectionDeserializer.deserialize(CollectionDeserializer.java:28)
	at com.fasterxml.jackson.databind.deser.impl.MethodProperty.deserializeAndSet(MethodProperty.java:129)
	at com.fasterxml.jackson.databind.deser.BeanDeserializer.vanillaDeserialize(BeanDeserializer.java:324)

Changing the Value object to allow Setters will avoid the NullPointerException from occurring:

- return JsonIgnoreProperties.Value.forIgnoredProperties("CanBeAnyValue");
+ return JsonIgnoreProperties.Value.forIgnoredProperties("CanBeAnyValue").withAllowSetters();

Version Information

Affects starting from 2.12.0, confirmed issue still present through 2.17.0-rc1.

Reproduction

Here is a sample project to reproduce the issue
reproduce-project.zip

pom.xml

<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 https://maven.apache.org/xsd/maven-4.0.0.xsd">
  <modelVersion>4.0.0</modelVersion>
  <groupId>sample</groupId>
  <artifactId>test</artifactId>
  <version>0.0.1-SNAPSHOT</version>
  <dependencies>
    <dependency>
      <groupId>com.fasterxml.jackson.core</groupId>
      <artifactId>jackson-databind</artifactId>
      <version>2.12.0</version>
    </dependency>
    <dependency>
      <groupId>org.junit.jupiter</groupId>
      <artifactId>junit-jupiter-api</artifactId>
      <version>5.10.2</version>
    </dependency>
  </dependencies>
  <build>
    <plugins>
      <plugin>
      <groupId>org.apache.maven.plugins</groupId>
      <artifactId>maven-compiler-plugin</artifactId>
      <configuration>
        <source>17</source>
        <target>17</target>
      </configuration>    
      </plugin>
    </plugins>
  </build>
</project>

src/test/java/test/ReproduceTest.java

package sample;

import java.util.List;

import org.junit.jupiter.api.Assertions;
import org.junit.jupiter.api.Test;

import com.fasterxml.jackson.annotation.JsonIgnoreProperties;
import com.fasterxml.jackson.annotation.JsonIgnoreProperties.Value;
import com.fasterxml.jackson.databind.ObjectMapper;
import com.fasterxml.jackson.databind.cfg.MapperConfig;
import com.fasterxml.jackson.databind.introspect.Annotated;
import com.fasterxml.jackson.databind.introspect.JacksonAnnotationIntrospector;

class ReproduceTest {

    /**
     * A simple recursive data structure to reproduce the issue
     */
    public static class Item {
        List<Item> items;
        public List<Item> getItems() {
            return items;
        }        
        public void setItems(List<Item> items) {
            this.items = items;
        }
    }
    
    // Sample JSON has one recursion of the items list
    String testJson = """
        {"items": [{"items": []}]}
        """;

    /**
     * This test will fail with error:
     * 
     * <pre>
        com.fasterxml.jackson.databind.JsonMappingException: 
          Cannot invoke "com.fasterxml.jackson.databind.JsonDeserializer.getObjectIdReader()" because "valueDes" is null (through reference chain: test.ReproduceTest$Item["items"]->java.util.ArrayList[0]->test.ReproduceTest$Item["items"])
     * </pre>
     */
    @Test
    void testReproduceJackonMapperNPE() throws Exception {
        runTest(new JacksonAnnotationIntrospector() {
            @Override
            public Value findPropertyIgnoralByName(MapperConfig<?> config, Annotated a) {
               return JsonIgnoreProperties.Value.forIgnoredProperties("CanBeAnyValue");
            }
        });
    }

    /**
     * This test will pass without exception when using withAllowSetters()
     */
    @Test
    void testAllowingSettersAvoidsNPE() throws Exception {
        runTest(new JacksonAnnotationIntrospector() {
            @Override
            public Value findPropertyIgnoralByName(MapperConfig<?> config, Annotated a) {
                return JsonIgnoreProperties.Value.forIgnoredProperties("CanBeAnyValue").withAllowSetters();
            }
        });
    }
    
    private void runTest(JacksonAnnotationIntrospector introspector) throws Exception {
        ObjectMapper mapper = new ObjectMapper();
        mapper.setAnnotationIntrospector(introspector);
        Item result = mapper.readValue(testJson, Item.class);
        Assertions.assertEquals(1, result.getItems().size(), 1);
    }
}

Build with Java 17 and mvn clean test

Expected behavior

I thought object should deserialize without hitting NPE without needing to explicitly configure withAllowSetters().

Additional context

No response

[cowtowncoder]

Ok looks like somehow CollectionDeserializer._valueDeserializer is left uninitialized, possibly related to recursive definition and contextualization (but possibly not).
Use of ignored properties will probably construct a new instance of CollectionDeserializer and something is either not copied correctly, or the old instance is referenced somewhere instead of newly created copy.

I don't know of immediate fix but it's good there is a reproduction.

[cowtowncoder]

And yes, it certainly looks like it may well be same root cause as #1755.
We do have failing test for that so it affects 2.16/2.17 as well.

[cowtowncoder]

Added failing test for this along with one or #1755, failure looks identical fwtw.

[cowtowncoder]

I think I'll close this one as duplicate: test can remain, but our backlog is so big that I'll try to aggressively prune it.