fix(kotlin): keep null-valued columns when casting response data

[abnegate]

What

• Fix: jsonCast() in the Android and Kotlin templates now serializes with requestGson, which calls serializeNulls(), instead of the default gson.
• Tests: a new JsonCastTest in both SDKs.

Why

jsonCast() builds Row.data/Document.data from the response map, and it used the default Gson, which omits nulls. So on Android and Kotlin a column whose value is null disappeared from row.data:

• Null and unselected look the same: a row with note: null read the same as a row whose query never selected note.
• Left joins lose columns: an unmatched left join lost its joined columns (c.name) instead of returning them as null.
• Realtime payloads cast through jsonCast() lost null fields the same way.

Web, Node, Python, PHP, Dart, React Native and Apple all keep them.

Found while running the query-lib case suite, 47 cases plus a builder chain, through every popular SDK against server-ce main. Every SDK except Android matched the web SDK exactly. Android differed only in null-valued keys: note on 40 rows, and c.name/customers.name on unmatched left-join rows.

Before / after

Check	main	This PR
JsonCastTest (Kotlin, JVM)	2 fail (AssertionError at the containsKey checks)	2/2 pass
JsonCastTest (Android, JVM unit)	2 fail (AssertionError at the containsKey checks)	2/2 pass
Query case suite through the Android SDK on an emulator (API 36) against server-ce main	15/48 cases identical to web (null keys missing)	48/48 identical

ktlint 1.8.0 is clean on the generated Kotlin and Android SDKs.

🤖 Generated with Claude Code

[hansi-codes]

🟢 Tier S · Ready to merge

The updated tests still exercise null preservation for flat and nested maps, and I found no issue in these incremental changes.

The Kotlin and Android templates now serialize jsonCast() inputs with null-preserving Gson, so null-valued response columns survive conversion. Both generated SDKs register tests for null keys in flat maps and nested response data.

Latest changes: The newest commits replace the Row-model-specific test cases with nested response-data map casts, avoiding a dependency on a generated Row model in the test fixture.

Verdict	New comments	Fixed	Still open
✅ Approved	0	0	0

📂 Walkthrough · 6

File	Change
src/SDK/Language/Android.php	Registers the generated Android JsonCast test.
src/SDK/Language/Kotlin.php	Registers the generated Kotlin JsonCast test.
templates/android/library/src/main/java/io/package/extensions/JsonExtensions.kt.twig	Uses null-preserving Gson for both Android jsonCast overloads.
templates/android/library/src/test/java/io/package/JsonCastTest.kt.twig	Tests null preservation for flat casts and nested response data.
templates/kotlin/src/main/kotlin/io/appwrite/extensions/JsonExtensions.kt.twig	Uses null-preserving Gson for both Kotlin jsonCast overloads.
templates/kotlin/src/test/kotlin/io/appwrite/JsonCastTest.kt.twig	Tests null preservation for flat casts and nested response data.

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_{Reviewed the commits since dde554f · Details · Comment @hansi-codes review to re-run, or mention @hansi-codes with a question.}

[hansi-codes]

🟢 Tier S · Looks good to merge. Summary