[WIP] Fix IReadOnlyDictionary treated as array-like on serialization

[Copilot]

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Original prompt

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This section details on the original issue you should resolve

<issue_title>IReadOnlyDictionary is treated as array-like</issue_title>
<issue_description>

Discussed in #2206

^{Originally posted by SebastianStehle December 5, 2025}

I am not sure yet, if this is a bug. I have a custom IReadOnlyDictionary that gets treated as array like. Therefore it will also be serialized as array when I use toJSON.

I think the culprit is here:

jint/Jint/Runtime/Interop/TypeDescriptor.cs

Line 166 in 768b442

isDictionary = typeof(IDictionary).IsAssignableFrom(type);

Is there something I can do to prevent that?

<agent_instructions>read the discussion and find optimal solution, create test coverage to show the problem, then fix fit</agent_instructions>

Comments on the Issue (you are @copilot in this section)

• Fixes IReadOnlyDictionary is treated as array-like #2284

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[lahma]

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