JsonSetter.contentNulls propagates unexpectedly into nested structures

[k163377]

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Describe the bug

JsonSetter.contentNulls should fundamentally only apply to the explicitly provided parameters.
That is, if this specification is applied to a parameter like List<List<String>>, [null] should be rejected, but [[null]] should be allowed.

However, in practice, [[null]] is rejected.

Version Information

3.1.0

Reproduction

import static org.junit.jupiter.api.Assertions.assertDoesNotThrow;
import static org.junit.jupiter.api.Assertions.assertThrows;

public class Kotlin1064Test {
    record Dst(
            @JsonSetter(contentNulls = Nulls.FAIL)
            List<List<String>> foo
    ) {}

    @Test
    public void test() {
        var mapper = JsonMapper.builder().build();

        assertThrows(InvalidNullException.class, () -> mapper.readValue("{\"foo\":[null]}", Dst.class));
        // fails
        assertDoesNotThrow(() -> mapper.readValue("{\"foo\":[[null]]}", Dst.class));
    }
}

Expected behavior

No response

Additional context

This relates to the following issues.
FasterXML/jackson-module-kotlin#1064

While it's hard to say what behavior is ideal, having Nulls.FAIL applied to the entire nested structure feels a bit cumbersome to handle.

Also, I don't have a specific design in mind yet, but I feel that fundamentally, we might need to change the structure of JsonSetter.

[cowtowncoder]

I think I agree (if I understand this correctly) that this is problematic; and also that setting should only apply to the immediate content level (Collection/array element, Map value).
Thank you for providing the failing test.

I think there was specific technical challenge in figuring out where within nested containers setting should apply to. And the problem is unfortunately not so much with @JsonSetter annotation but in how checking is applied for deserializer -- all List deserializer in this case apply the same setting. So somehow deserializer would need to know whether it is the deserializer for outermost List (should apply) or not (should not apply).

But hopefully this can be figured out.

[dlwldnjs1009]

I've submitted a PR for this: #5751

It adds a _contentProperty() helper in StdDeserializer so nested content
deserializers do not keep reading the outer property's annotation-level
contentNulls. Inner-level contentNulls is recalculated from the nested
content type's ConfigOverride or global default.

The change covers CollectionDeserializer, MapDeserializer,
EnumMapDeserializer, and ObjectArrayDeserializer.

ReferenceTypeDeserializer and MapEntryDeserializer follow the same pattern,
but I left those for follow-up to keep this PR focused on the reported issue.