Fix json encoder to reject user defined iterables

[GKotsifos]

Fixes Json Module should output type error on iterables that are not encodable

Description of changes in release / Impact of release:

Updates the JSON encoder to reject user-defined iterables, raising a TypeError instead of serializing them as arrays.

Documentation

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Risks of this release

Is this a breaking change?

• Yes
• No

If you answered Yes then describe why is it so

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Is there a way to disable the change?

• Use previous release
• Use a feature flag
• No

Additional details go here

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[mahmoudimus]

Do we have a test for this? I understand why, but would this break behavior that folks are depending on?

[GKotsifos]

Fair point, if anyone is serializing custom iterables then this change will break them. Regarding the test, I was thinking of adding one but saw this line:

starlarky/larky/src/main/java/com/verygood/security/larky/modules/JsonModule.java

Line 36 in ae1cc24

// Tests at //src/test/java/net/starlark/java/eval:testdata/json.star

and could not find a json.star file so I assumed there are not tests for json. I can create some if needed.

[mahmoudimus]

@GKotsifos the tests are here, I can see how that's confusing:

https://github.com/verygoodsecurity/starlarky/blob/master/libstarlark/src/test/java/net/starlark/java/eval/testdata/json.star

Maybe update the comment to say it's at libstarlark/...

[GKotsifos]

@mahmoudimus correct me if I am wrong but these tests are for this class:

https://github.com/verygoodsecurity/starlarky/blob/master/libstarlark/src/main/java/net/starlark/java/lib/json/Json.java

and not the JsonModule.java where the changes are:

https://github.com/verygoodsecurity/starlarky/blob/master/larky/src/main/java/com/verygood/security/larky/modules/JsonModule.java

although now that you mention it we should probably apply the same fix to Json.java as well.

Also looking at these tests, I saw this line:

starlarky/libstarlark/src/test/java/net/starlark/java/eval/testdata/json.star

Line 31 in ae1cc24

assert_eq(json.encode(range(3)), "[0,1,2]") # a built-in iterable

where even though range is a built-in iterable it should still fail since in python only lists and tuples are mapped by default to JSON arrays and I assume we want to mimic the exact behavior of python. But the description of the issue only states we should reject user-defined iterables. What do you think?