Code generators (model, client, response, serializers) by halotukozak · Pull Request #4 · AVSystem/justworks

halotukozak · 2026-03-11T19:49:47Z

Summary

ModelGenerator — data classes, sealed interfaces, enums, type aliases from OpenAPI schemas
ClientGenerator — per-tag Ktor HTTP client classes with suspend functions
ApiResponseGenerator — sealed ApiResponse hierarchy (HttpSuccess, HttpError)
SerializersModuleGenerator — kotlinx.serialization module for polymorphic types
TypeMapping, NameUtils, Names, InlineSchemaDeduplicator utilities
Full test coverage (8 test files)

Test plan

./gradlew core:test passes

Depends on #2

🤖 Generated with Claude Code

ModelGenerator, ClientGenerator, ApiResponseGenerator, SerializersModuleGenerator, TypeMapping, NameUtils, Names, InlineSchemaDeduplicator with full test coverage. Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Copilot

Pull request overview

This PR introduces the core OpenAPI→Kotlin code generation pipeline: parsing + validation of specs into an intermediate model, then generating Kotlin model types, Ktor clients, response wrappers, and serializers wiring—backed by comprehensive tests and fixtures.

Changes:

Added SpecParser + SpecValidator and expanded test fixtures for refs, polymorphism, anyOf/oneOf, and Swagger v2 conversion.
Implemented generators for models (ModelGenerator), clients (ClientGenerator), API responses (ApiResponseGenerator), and polymorphic serializers module (SerializersModuleGenerator), plus supporting utilities.
Added extensive unit tests across parsing, naming, type mapping, and code generation behavior.

Reviewed changes

Copilot reviewed 33 out of 33 changed files in this pull request and generated 10 comments.

Show a summary per file

File	Description
core/build.gradle.kts	Adds Arrow dependency and enables `-Xcontext-parameters`; pins ktlint version.
core/src/main/kotlin/com/avsystem/justworks/core/Generator.kt	Adds generator entry point placeholder.
core/src/main/kotlin/com/avsystem/justworks/core/gen/ApiResponseGenerator.kt	Generates `HttpError`/`HttpErrorType` and `HttpSuccess<T>` KotlinPoet files.
core/src/main/kotlin/com/avsystem/justworks/core/gen/ClientGenerator.kt	Generates per-tag Ktor client classes and endpoint suspend functions.
core/src/main/kotlin/com/avsystem/justworks/core/gen/InlineSchemaDeduplicator.kt	Implements inline schema structural deduplication and collision handling.
core/src/main/kotlin/com/avsystem/justworks/core/gen/ModelGenerator.kt	Generates models (data classes, sealed interfaces, type aliases), polymorphic serializers, and inline schema classes.
core/src/main/kotlin/com/avsystem/justworks/core/gen/NameUtils.kt	Provides casing/name utilities and Kotlin keyword escaping.
core/src/main/kotlin/com/avsystem/justworks/core/gen/Names.kt	Centralizes KotlinPoet `ClassName`/`MemberName` references used by generators.
core/src/main/kotlin/com/avsystem/justworks/core/gen/SerializersModuleGenerator.kt	Generates `SerializersModule` registrations for sealed hierarchies.
core/src/main/kotlin/com/avsystem/justworks/core/gen/TypeMapping.kt	Maps intermediate `TypeRef` to KotlinPoet `TypeName`.
core/src/main/kotlin/com/avsystem/justworks/core/model/ApiSpec.kt	Defines intermediate API model (spec/endpoints/schemas/enums/type refs).
core/src/main/kotlin/com/avsystem/justworks/core/model/TypeRef.kt	Defines `TypeRef` hierarchy and primitive types.
core/src/main/kotlin/com/avsystem/justworks/core/parser/SpecParser.kt	Parses OpenAPI/Swagger into intermediate model; handles combinators/refs/wrapper patterns.
core/src/main/kotlin/com/avsystem/justworks/core/parser/SpecValidator.kt	Validates parsed OpenAPI input and surfaces issues/warnings.
core/src/test/kotlin/com/avsystem/justworks/core/gen/ApiResponseGeneratorTest.kt	Tests for `HttpError`/`HttpSuccess` code generation.
core/src/test/kotlin/com/avsystem/justworks/core/gen/ClientGeneratorTest.kt	Tests client generation (methods, params, auth header, error handling, polymorphism wiring).
core/src/test/kotlin/com/avsystem/justworks/core/gen/InlineSchemaDedupTest.kt	Tests inline schema deduplication and name collision behavior.
core/src/test/kotlin/com/avsystem/justworks/core/gen/ModelGeneratorPolymorphicTest.kt	Tests oneOf/anyOf/discriminator handling, polymorphic serializer generation, and allOf interactions.
core/src/test/kotlin/com/avsystem/justworks/core/gen/ModelGeneratorTest.kt	Tests model generation (data classes, enums, defaults, keyword escaping, type aliases).
core/src/test/kotlin/com/avsystem/justworks/core/gen/NameUtilsTest.kt	Tests casing, enum constant naming, Kotlin identifier escaping, and operation naming.
core/src/test/kotlin/com/avsystem/justworks/core/gen/SerializersModuleGeneratorTest.kt	Tests serializers module generation for sealed hierarchies.
core/src/test/kotlin/com/avsystem/justworks/core/gen/TypeMappingTest.kt	Tests `TypeRef` → KotlinPoet type mapping.
core/src/test/kotlin/com/avsystem/justworks/core/parser/SpecParserPolymorphicTest.kt	Tests parsing behavior for polymorphic and allOf specs.
core/src/test/kotlin/com/avsystem/justworks/core/parser/SpecParserTest.kt	Tests core parsing, $ref resolution, error reporting, anyOf rules, and v2 conversion.
core/src/test/kotlin/com/avsystem/justworks/core/parser/SpecValidatorTest.kt	Tests validator behavior for missing required `info`.
core/src/test/resources/anyof-spec.yaml	Fixture for anyOf parsing/generation behavior.
core/src/test/resources/anyof-valid-spec.yaml	Fixture for anyOf + discriminator parsing behavior.
core/src/test/resources/invalid-spec.yaml	Fixture for validator/parser failure behavior.
core/src/test/resources/mixed-combinator-spec.yaml	Fixture ensuring mixed combinators raise an error.
core/src/test/resources/petstore-v2.json	Swagger v2 fixture for conversion testing.
core/src/test/resources/petstore.yaml	OpenAPI v3 fixture for baseline parsing tests.
core/src/test/resources/polymorphic-spec.yaml	Polymorphism fixture (oneOf, discriminator, allOf).
core/src/test/resources/refs-spec.yaml	Fixture for exercising various $ref resolution patterns.

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Copilot · 2026-03-11T19:55:18Z

core/src/main/kotlin/com/avsystem/justworks/core/gen/ClientGenerator.kt

+        val builder = CodeBlock
+            .builder()
+            .add("%T·{\n", HTTP_CLIENT)
+            .indent()
+            .add("install(%T)·{\n", CONTENT_NEGOTIATION)
+            .indent()


The CodeBlock templates in buildClientInitializer contain literal '·' characters (e.g., "%T·{", "expectSuccess·=·false"). These will be emitted into the generated Kotlin source and will not compile; use normal spaces/newlines and let KotlinPoet handle indentation instead of embedding this marker character.

Copilot · 2026-03-11T19:55:19Z

core/src/main/kotlin/com/avsystem/justworks/core/gen/ModelGenerator.kt

+                builder.addStatement(
+                    "%S·in·element.%M -> %T.serializer()",
+                    uniqueField,
+                    JSON_OBJECT_EXT,
+                    variantClassName,
+                )


The generated when branch uses literal '·' characters in the statement format string ("%S·in·element..."), which will be emitted into the generated Kotlin code and cause compilation failures. Remove these marker characters and rely on KotlinPoet formatting/indentation.

Copilot · 2026-03-11T19:55:19Z

core/src/main/kotlin/com/avsystem/justworks/core/gen/ModelGenerator.kt

+            } else {
+                builder.addStatement(
+                    "// No unique discriminating fields found for variant '$variantName'",
+                )
+                builder.addStatement(
+                    "else -> TODO(%S)",
+                    "No unique discriminating fields found for variant '$variantName' of anyOf '$parentName' - manual selectDeserializer required",
+                )


else -> TODO(...) is emitted inside the loop over variants, which can produce multiple else branches in the same when (invalid Kotlin) and also makes later variant checks unreachable. Emit variant-specific conditions in the loop and add a single final else branch after the loop (either TODO or a SerializationException).

Copilot · 2026-03-11T19:55:19Z

core/build.gradle.kts

 }
+val compileKotlin: KotlinCompile by tasks
+compileKotlin.compilerOptions {
+    freeCompilerArgs.set(listOf("-Xcontext-parameters"))


freeCompilerArgs.set(listOf("-Xcontext-parameters")) overwrites any existing compiler args configured by other plugins/tasks. Prefer appending (e.g., add) to preserve defaults and avoid surprising build changes as the build grows.

Suggested change

freeCompilerArgs.set(listOf("-Xcontext-parameters"))

freeCompilerArgs.add("-Xcontext-parameters")

Copilot · 2026-03-11T19:55:19Z

core/src/main/kotlin/com/avsystem/justworks/core/gen/ClientGenerator.kt

+        code.addStatement(
+            "append(%T.Authorization, %P)",
+            HTTP_HEADERS,
+            CodeBlock.of($$"Bearer ${'$'}{$tokenProvider}"),


This header value CodeBlock uses $$"..." which is not valid Kotlin syntax, so the generator itself will not compile. Build the "Bearer " string using standard Kotlin string/CodeBlock formatting, and reference the tokenProvider property correctly (e.g., as a lambda invocation if that's the intent).

Suggested change

CodeBlock.of($$"Bearer ${'$'}{$tokenProvider}"),

CodeBlock.of("\"Bearer ${'$'}{tokenProvider()}\""),

Copilot · 2026-03-11T19:55:20Z

core/src/main/kotlin/com/avsystem/justworks/core/gen/ClientGenerator.kt

+                    FunSpec
+                        .constructorBuilder()
+                        .addParameter("baseUrl", STRING)
+                        .addParameter("tokenProvider", STRING)
+                        .build(),


tokenProvider is modeled as a String, but its name and usage imply it should provide a token dynamically (e.g., () -> String or suspend () -> String). Keeping it as a String makes token refresh impossible and is likely to produce incorrect Authorization headers for long-lived clients.

Copilot · 2026-03-11T19:55:20Z

core/src/main/kotlin/com/avsystem/justworks/core/gen/ModelGenerator.kt

+import com.squareup.kotlinpoet.TypeSpec
+import com.squareup.kotlinpoet.asTypeName
+import java.io.File
+import kotlin.time.Instant


kotlin.time.Instant is imported here, but Kotlin doesn't provide an Instant type in kotlin.time (Instant is in kotlinx-datetime / java.time). This import will break compilation; use kotlinx.datetime.Instant (or fully qualify) for the parse-time validation logic.

Suggested change

import kotlin.time.Instant

import kotlinx.datetime.Instant

Copilot · 2026-03-11T19:55:20Z

core/src/main/kotlin/com/avsystem/justworks/core/gen/ModelGenerator.kt

+                PrimitiveType.DATE_TIME -> {
+                    // Validate at generation time
+                    try {
+                        Instant.parse(prop.defaultValue as String)
+                        "kotlin.time.Instant.parse(\"${prop.defaultValue}\")"
+                    } catch (e: Exception) {


For DATE_TIME defaults, the generator both validates with Instant.parse(...) and emits kotlin.time.Instant.parse(...) into generated code. This will not compile and also doesn't match the repo's datetime dependency (kotlinx-datetime). Use kotlinx.datetime.Instant.parse(...) consistently for validation and emitted default values.

Copilot · 2026-03-11T19:55:20Z

core/src/main/kotlin/com/avsystem/justworks/core/gen/ModelGenerator.kt

+                        isPrimitiveOnly(schema) -> {
+                            // For primitive-only schemas, generate type alias
+                            // TODO: Extend SchemaModel to include primitiveType field for primitive-only schemas
+                            // For now, defaulting to String as the most common case
+                            listOf(generateTypeAlias(schema, STRING))


Primitive-only schemas are currently emitted as typealias <Name> = String regardless of the actual OpenAPI primitive type/format. This will generate incorrect models for type: integer/number/boolean/.... Either extend the parsed model to retain the primitive type for such schemas or avoid type-alias generation until that information is available.

Copilot · 2026-03-11T19:55:21Z

core/src/main/kotlin/com/avsystem/justworks/core/parser/SpecParser.kt

+
+            "array" -> items?.toTypeRef()?.let(TypeRef::Array) ?: TypeRef.Primitive(PrimitiveType.STRING)
+
+            "object" -> (additionalProperties as? Schema<*>)?.toTypeRef()


OpenAPI type: object with additionalProperties represents a map, but this branch returns the value type directly instead of wrapping it as TypeRef.Map(...). This loses the map structure and will cause the generator to treat maps as their value type; return TypeRef.Map(valueType) here.

Suggested change

"object" -> (additionalProperties as? Schema<*>)?.toTypeRef()

"object" -> (additionalProperties as? Schema<*>)?.toTypeRef()?.let(TypeRef::Map)

feat: add code generators (model, client, response, serializers)

fb1a202

ModelGenerator, ClientGenerator, ApiResponseGenerator, SerializersModuleGenerator, TypeMapping, NameUtils, Names, InlineSchemaDeduplicator with full test coverage. Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Copilot AI review requested due to automatic review settings March 11, 2026 19:49

Copilot started reviewing on behalf of halotukozak March 11, 2026 19:50 View session

halotukozak mentioned this pull request Mar 11, 2026

Gradle plugin with multi-spec support #5

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Copilot AI reviewed Mar 11, 2026

View reviewed changes

halotukozak changed the base branch from master to feat/model-parser March 11, 2026 19:55

halotukozak changed the base branch from feat/model-parser to master March 12, 2026 14:17

halotukozak changed the base branch from master to feat/model-parser March 12, 2026 14:18

fix: resolve ktlint no-consecutive-comments violation in Names.kt

e097013

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Code generators (model, client, response, serializers)#4

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	freeCompilerArgs.set(listOf("-Xcontext-parameters"))
	freeCompilerArgs.add("-Xcontext-parameters")

	CodeBlock.of($$"Bearer ${'$'}{$tokenProvider}"),
	CodeBlock.of("\"Bearer ${'$'}{tokenProvider()}\""),


		"array" -> items?.toTypeRef()?.let(TypeRef::Array) ?: TypeRef.Primitive(PrimitiveType.STRING)

		"object" -> (additionalProperties as? Schema<*>)?.toTypeRef()

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