feat: implement @AutoGenerateField KSP plugin for auto-generating PreviewLabField factories

[TBSten]

Summary

• Implemented a Kotlin Symbol Processing (KSP) plugin that automatically generates factory functions for PreviewLabField
• Added @AutoGenerateField<T> annotation for marking objects to auto-generate field factories
• Supports automatic generation for Primitives, Enums, Objects, Data Classes, and Sealed Types
• Significantly reduces boilerplate code for common field type definitions

Changes

Core Implementation

• TypeClassification.kt: Sealed interface for type classification (Primitive, Enum, Object, DataClass, Sealed, Unsupported)
• TypeClassifier.kt: Classifies KSType into TypeClassification categories with caching support
• CodeGenerator.kt: Generates extension functions and helper objects based on type classification
• AutoGenerateFieldProcessor.kt: Main processor orchestrating the code generation workflow

New APIs

• @AutoGenerateField<T>(name: String = "", autoLabelByTypeName: Boolean = false): Annotation for auto-generation
• ChildFieldScope<Value>: Scope class for accessing label and initialValue in child field factories
• enumField(): Helper function for enum field generation

Gradle Integration

• Added generateAutoField property to ComposePreviewLabExtension (default: true)
• Configured KSP argument passing from Gradle Plugin

Test Infrastructure

• Created integrationTest/autoGenerateFieldTest module for compile-time verification
• Defined test types covering all supported classifications (T1-T5):
  • T1: Primitive types (String, Int)
  • T2: Enum (SimpleStatus)
  • T3: Object types (SingletonState, EmptyState)
  • T4: Data Class (SimpleData with nested fields)
  • T5: Sealed Interface (SimpleSealed with multiple subclasses)

Generated Code Examples

Primitive Type

fun Fields.string(label: String, initialValue: String): MutablePreviewLabField<String>

Enum Type

fun Fields.simpleStatus(label: String, initialValue: SimpleStatus): MutablePreviewLabField<SimpleStatus>

Data Class (Combined Field)

fun Fields.simpleData(
    label: String,
    initialValue: SimpleData,
    nameField: ChildFieldScope<String>.() -> MutablePreviewLabField<String> = ...,
    countField: ChildFieldScope<Int>.() -> MutablePreviewLabField<Int> = ...,
): MutablePreviewLabField<SimpleData>

Test plan

• Ran ./gradlew ktlintCheck - All style checks pass
• Ran ./gradlew :ksp-plugin:build :gradle-plugin:build - Build successful
• Ran cd integrationTest && ./gradlew :autoGenerateFieldTest:compileCommonMainKotlinMetadata - KSP code generation successful
• Ran ./gradlew :autoGenerateFieldTest:compileKotlinJvm - Generated code compiles correctly
• Verified generated code includes @file:OptIn(ExperimentalComposePreviewLabApi::class)
• Verified API dumps updated for annotation, field, gradle-plugin, ksp-plugin modules
• Manual verification: Generated factory functions are correct and type-safe

🤖 Generated with Claude Code

Co-Authored-By: Claude [email protected]

[Copilot]

Pull request overview

This PR implements a Kotlin Symbol Processing (KSP) plugin that automatically generates factory functions for creating PreviewLabField instances. The plugin uses the new @AutoGenerateField<T> annotation to mark types for code generation, significantly reducing boilerplate when defining preview fields for various Kotlin types.

Key Changes

• Introduced KSP-based code generation supporting primitives, enums, objects, data classes, and sealed types
• Added @AutoGenerateField<T> annotation with configurable name and automatic labeling options
• Integrated with existing Gradle plugin via generateAutoField property (enabled by default)

Reviewed changes

Copilot reviewed 24 out of 24 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
ksp-plugin/src/main/kotlin/.../TypeClassification.kt	Defines sealed interface for categorizing Kotlin types with metadata
ksp-plugin/src/main/kotlin/.../TypeClassifier.kt	Implements type classification logic with caching
ksp-plugin/src/main/kotlin/.../CodeGenerator.kt	Generates factory extension functions based on type classification
ksp-plugin/src/main/kotlin/.../AutoGenerateFieldProcessor.kt	Main KSP processor coordinating code generation workflow
ksp-plugin/src/main/kotlin/.../ComposePreviewLabKspProcessor.kt	Integrates AutoGenerateField processor into existing KSP pipeline
field/src/commonMain/kotlin/.../EnumField.kt	Adds helper functions for enum field creation
field/src/commonMain/kotlin/.../ChildFieldScope.kt	New scope class providing context for child field factories
gradle-plugin/src/main/kotlin/.../ComposePreviewLabExtension.kt	Adds generateAutoField configuration property
annotation/src/commonMain/kotlin/.../AutoGenerateField.kt	New annotation for marking types for auto-generation
annotation/src/commonMain/kotlin/.../KspArg.kt	Adds KSP argument constant for feature flag
integrationTest/autoGenerateFieldTest/*	Integration test module verifying generated code compiles
/api/	Updated API dumps for public API changes

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