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Unity fake-null

obj == null returns true on a destroyed UnityEngine.Object even when the managed C# wrapper is still alive. Reflection walks that dereference fields on such wrappers crash with MissingReferenceException. Required reading for any code that walks arbitrary object graphs (serializers, diagnostic dumpers).

Problem

Unity overrides == on UnityEngine.Object to compare against "native-object-destroyed" as well as C# null. A destroyed GameObject / Component / Transform returns obj == null as true even though the managed wrapper is a live reference. Code that null-checks with == null is safe. Code that dereferences after passing is object or after a referenceEquals(obj, null) == false check is not.

The trap bites reflection walkers and serializers because their generic "recurse into non-null fields" logic uses reference-null checks, not Unity's override.

F0004 (Mods/InspectorPlus/RESEARCH.md:25-29):

Reflection against Unity fake-null is a known trap (obj == null returns true even when the managed wrapper is still alive). The walker checks UnityEngine.Object-derived values via !obj before dereferencing.

Solution / recipe

Before dereferencing any UnityEngine.Object-derived value that reflection surfaces, gate on Unity's own equality. Two equivalent forms:

if (!value)  // invokes Unity's implicit bool conversion via operator==
    return;  // destroyed or null

// or explicitly:
if (value == null)
    return;

A reference-null check (object.ReferenceEquals(value, null)) is NOT equivalent and will let through destroyed wrappers.

When the field type is not statically known (a generic object from reflection), test the runtime type first:

if (value is UnityEngine.Object unityObj && !unityObj)
    return;  // destroyed Unity object

Apply this rule to every recursion frame in a walker, not just the entry point. A destroyed child can hang off a live parent.

Verification history

  • 2026-04-20: page created from the Research migration; content lifted verbatim from F0004.

Open questions

None at creation.