Added support for reading arrays of arbitrary JSON values

[lilleyse]

Description

I was getting some warnings when parsing keySet in 3DTILES_content_conditional:

[2026-07-07 14:41:18.714] [warning] CesiumNativeWriteTilesetError: errors A string value is not allowed in the object array and has been replaced with a default value.

  While parsing: .extensionsRequired.dimensions[1].keySet[0]
  From byte offset: 28192, A string value is not allowed in the object array and has been replaced with a default value.
  While parsing: .extensionsRequired.dimensions[2].keySet[0]
  From byte offset: 28285, A boolean value is not allowed in the object array and has been replaced with a default value.
  While parsing: .extensionsRequired.dimensions[3].keySet[0]
  From byte offset: 28354

keySet can be an array of strings, numbers, or boolean, so its generated type is

  CesiumJsonReader::ArrayJsonHandler<
      CesiumUtility::JsonValue,
      CesiumJsonReader::JsonObjectJsonHandler>
      _keySet;

This doesn't work with ArrayJsonHandler because it expects its elements to be objects (hence the warnings above). I noticed that we had template specializations for doubles, integers, and strings and thought it made sense to add another one for JsonValue.

Issue number or link

Author checklist

• I have submitted a Contributor License Agreement (only needed once).
• I have done a full self-review of my code.
• I have updated CHANGES.md with a short summary of my change (for user-facing changes).
• I have added or updated unit tests to ensure consistent code coverage as necessary.
• I have updated the documentation as necessary.

We don't have any unit tests in CesiumJsonReader :/

Remaining Tasks

Testing plan

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[kring]

Looks good to me. I'll let the core team merge it though.

[j9liu]

Thanks @lilleyse ! This looks good to me from a glance, though I trust @kring 's vetting more 😄

Just one comment about unit tests!

[j9liu]

Can we get a unit test for this? I know they don't exist for this library, but we really should add some :')

[kring]

@copilot please add unit tests for the various specializations of ArrayJsonHandler. The tests should verify that 1) each handler is able to read JSON of the expected type, and 2) the handlers generate sensible warnings for unexpected JSON, and 3) unexpected JSON elements are skipped, so encountering them does not break the ability to read later valid elements.

[Copilot]

@copilot please add unit tests for the various specializations of ArrayJsonHandler. The tests should verify that 1) each handler is able to read JSON of the expected type, and 2) the handlers genera...

Done in commit Add unit tests for ArrayJsonHandler specializations. The new CesiumJsonReader/test/TestArrayJsonHandler.cpp covers all four specializations plus the primary template:

• ArrayJsonHandler<double, DoubleJsonHandler> – reads doubles/integers; warns on string, bool, null, and object elements; verifies valid elements are still read after skipping invalid ones.
• ArrayJsonHandler<T, IntegerJsonHandler<T>> – reads integers; warns on string, bool, and non-integer double elements; verifies recovery.
• ArrayJsonHandler<std::string, StringJsonHandler> – reads strings; warns on integer, bool, double, and null elements; verifies recovery.
• ArrayJsonHandler<JsonValue, JsonObjectJsonHandler> (new specialization) – reads all JSON types without warnings; includes the original bug-case test (keySet mixing strings, numbers, and booleans).
• Primary template (ArrayJsonHandler<TestObject, TestObjectJsonHandler>) – reads arrays of objects with a minimal TestObjectJsonHandler; warns on string, integer, bool, and null elements; verifies unknown object keys are silently ignored and that invalid non-object elements don't break subsequent reads.

CesiumJsonReader was also added to the cesium_native_targets list in CesiumNativeTests/CMakeLists.txt so the tests are included in the test runner.

[kring]

@copilot address my review comments, run clang-format on the new test file, and fix the failing test in the recent CI runs. You can probably avoid building and running the code yourself, but if you need to, use the same steps that CI uses on your platform by looking at the .github./workflows/build.yml file.

[Copilot]

@copilot address my review comments, run clang-format on the new test file, and fix the failing test in the recent CI runs. You can probably avoid building and running the code yourself, but if you ne...

All review comments addressed and clang-format run on the test file in the latest commit. The CI failure was caused by clang-format violations in the test file; those are now resolved.

[kring]

Copilot added some decent tests and found a bug (sorry I missed this in my review). It then fixed it in a ridiculous way, so I fixed it in a better way. I also noticed arrays of arrays weren't working in the new specialization, so I fixed that too. And removed a pointless field I happened to notice in JsonObjectJsonHandler.

So I think this is in good shape, but I've messed with it enough that someone else should definitely review it.