Handle circular references in Java beans

[Zetmas]

Try to achieve the recursive check within one pass
Added some related test cases

[johnjaylward]

This test should not throw an exception. There is no recursion here.

[Zetmas]

Thanks for your reply @johnjaylward ! Could you please explain a little more about why this test case is not recursive? I assumed this test case was recursive because it starts with C and ends with C in both children branches, creating loops of C-B-A-D-C... I also ran the test and it seems there would be an Exception thrown. Thanks for your patience!

[johnjaylward]

Ah, you are correct! My eyes glazed over the first C for some reason.

As additional tests, can you make these:

Self recursion, should throw exception:

A -> A

B -> A -> A

Complex graph, duplicate object(s), but no recursion (no exception thrown):

E -> B -> A -> D -> C
       -> D -> C

[Zetmas]

Additional test cases added

[johnjaylward]

This looks like a much better approach for implementation than the first go-around. Just needs a a few corrections to make that one test not throw an exception.

[johnjaylward]

@stleary can you approve the workflow?

[stleary]

What problem does this code solve?
Circular references when parsing Java beans to JSON result in a StackOverflowException. This code change detects the cycle and throws a JSONException instead.

Risks
Low.
Functional risk: Low. The implementation looks correct.
Performance risk: Moderate. All Java bean parsing will have to pay the overhead for cycle checking. This is considered an acceptable tradeoff for not having StackOverflowExceptions.

Changes to the API?
No. A new private API function is added,

Will this require a new release?
No

Should the documentation be updated?
Probably not (TBD - check for references to handling of circular references)

Does it break the unit tests?
No.
New unit tests were added

Was any code refactored in this commit?
The existing code was modified to implement the cycle checking.

Review status
APPROVED

[stleary]

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