How to Prevent Stack Overflow in Go's `UnmarshalJSON`?

Preventing Stack Overflow in UnmarshalJSON by Intercepting the Unmarshal Call

In the context of custom UnmarshalJSON implementations, it can be necessary to perform additional steps during data structure initialization. However, invoking json.Unmarshal() within UnmarshalJSON can lead to a stack overflow because the JSON decoder repeatedly searches for a custom implementation, resulting in infinite recursion.

To avoid this issue, the underlying default implementation can be invoked without triggering the recursive loop. Here's how:

1. Create an Intermediate Type with the Type Keyword:

   • Define a new type using the type keyword, such as type person2 Person.

2. Type Conversion and Assignment:

   • Utilize type conversion to assign the original value to the new type, e.g., (*person2)(p). This will create a value of the new type without inheriting methods from the underlying type.

3. Invoke Default Unmarshal Function:

   • Call json.Unmarshal with the new type, which will invoke the default implementation.

4. Post-Processing (Optional):

   • Perform any necessary post-processing after the default unmarshaling, as required by the custom logic.

By employing this technique, the recursive loop is broken because the new type does not have the UnmarshalJSON method defined. This prevents a stack overflow and allows for seamless initialization with additional processing.

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