fix(prompt): resolve @Contextual properties in GenericJsonSchemaGenerator#1875
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Andrey Bragin (EugeneTheDev) merged 2 commits intoJun 2, 2026
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Hi Faraz Ahmed (@faraz152), thank you for the contribution! Please address the failing checks. |
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Hi @aozherelyeva, the failing checks have been addressed — the ktlint indentation issue in |
When a @serializable data class contains a @contextual property, GenericJsonSchemaGenerator.process() fell into the else branch and threw an IllegalArgumentException ("Encountered unsupported type: CONTEXTUAL"), aborting schema generation before any LLM request. Fix: add an explicit SerialKind.CONTEXTUAL branch that resolves the actual descriptor from the Json instance's SerializersModule via getContextualDescriptor() and delegates to process() recursively. If no contextual serializer is registered, a descriptive error now guides the user to register one or use @serializable(with = ...). Tests: three new cases in JsonSchemaGeneratorTest covering basic and standard generators with a registered contextual serializer, and the clear-error path when the serializer is absent. Fixes JetBrains#1486
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Looks good, thank you. I rebased it to the latest develop, will merge it once all checks are green
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…erator (#1875) `executeStructured` crashed with `IllegalArgumentException: Encountered unsupported type while generating JSON schema: CONTEXTUAL` when the response data class contained a `@Contextual` property (e.g. `java.util.UUID`, any non-`@Serializable` type registered via `SerializersModule`). `GenericJsonSchemaGenerator.process()` had no branch for `SerialKind.CONTEXTUAL`, so it fell through to the `else` clause and threw immediately — before any LLM request was made. Added an explicit `SerialKind.CONTEXTUAL` branch that: 1. Calls `serializersModule.getContextualDescriptor(descriptor)` (stable API in kotlinx.serialization 1.7+) to resolve the actual serializer registered in the `Json` instance's module. 2. Delegates to `process()` recursively with the resolved descriptor, so the type is generated correctly (e.g. a UUID serialized as a string → `"type": "string"`). 3. If no contextual serializer is found, throws a **descriptive** `IllegalArgumentException` explaining how to fix it (register via `SerializersModule { contextual(...) }` or use `@Serializable(with = ...)`). | File | Change | |---|---| | `GenericJsonSchemaGenerator.kt` | Add `SerialKind.CONTEXTUAL` branch; `@OptIn(ExperimentalSerializationApi::class)` on class | | `JsonSchemaGeneratorTest.kt` | 3 new test cases: basic generator, standard generator, and missing-serializer error path | ``` ./gradlew :prompt:prompt-structure:jvmTest --tests "ai.koog.prompt.structure.json.generator.JsonSchemaGeneratorTest" BUILD SUCCESSFUL ``` All 3 new tests pass alongside the existing suite. Use `@Serializable(with = MySerializer::class)` on the property instead of `@Contextual`, as noted in the issue. closes #1486 (cherry picked from commit 6ee3b63)
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What
Fixes #1486
executeStructuredcrashed withIllegalArgumentException: Encountered unsupported type while generating JSON schema: CONTEXTUALwhen the response data class contained a@Contextualproperty (e.g.java.util.UUID, any non-@Serializabletype registered viaSerializersModule).Root cause
GenericJsonSchemaGenerator.process()had no branch forSerialKind.CONTEXTUAL, so it fell through to theelseclause and threw immediately — before any LLM request was made.Fix
Added an explicit
SerialKind.CONTEXTUALbranch that:serializersModule.getContextualDescriptor(descriptor)(stable API in kotlinx.serialization 1.7+) to resolve the actual serializer registered in theJsoninstance's module.process()recursively with the resolved descriptor, so the type is generated correctly (e.g. a UUID serialized as a string →"type": "string").IllegalArgumentExceptionexplaining how to fix it (register viaSerializersModule { contextual(...) }or use@Serializable(with = ...)).Changes
GenericJsonSchemaGenerator.ktSerialKind.CONTEXTUALbranch;@OptIn(ExperimentalSerializationApi::class)on classJsonSchemaGeneratorTest.ktTesting
All 3 new tests pass alongside the existing suite.
Workaround (before this fix)
Use
@Serializable(with = MySerializer::class)on the property instead of@Contextual, as noted in the issue.