Circular Reference Causes StackOverflowError in JsonWriter

[testmigrator]

While writing a test case for circular reference serialization, I discovered that the current implementation of JsonWriter does not handle circular references properly, leading to a StackOverflowError.

@Test
public void testCircularReferenceSerialization() {
    // Create a dictionary and introduce a circular reference by setting one of its values to be the dictionary itself.
    JsonObject dict = new JsonObject(16, 0.75f);
    dict.put("a", dict);

    // Attempt to serialize the dictionary using a JSON serialization method.
    JsonWriter jsonWriter = new JsonWriter();
    try {
        jsonWriter.string(dict);
        fail("Expected a ValueError indicating the presence of a circular reference.");
    } catch (IllegalArgumentException e) {
        assertTrue(e.getMessage().contains("circular reference"), "The exception message should indicate a circular reference.");
    }
}

Expected Behavior:

The JsonWriter should detect the circular reference and throw an IllegalArgumentException with a message indicating the presence of a circular reference.

Actual Behavior:

The JsonWriter enters an infinite recursion due to the circular reference, resulting in a StackOverflowError.

Proposed Solution:

To handle circular references, the JsonWriter (or its base class, JsonWriterBase) should implement a mechanism to track visited objects during serialization. If a circular reference is detected, an exception should be thrown to prevent infinite recursion.

[testmigrator]

This test is based on a real test from the Python simplejson library.

Thanks again for your time and effort on this project. Looking forward to your response!