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fix: prevent StackOverflow on self-referencing types and remap lambda receiver #24

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Merged
wilmveel merged 1 commit into from
Mar 27, 2026
Merged

fix: prevent StackOverflow on self-referencing types and remap lambda receiver #24

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10 changes: 6 additions & 4 deletions ...r-plugin/src/main/kotlin/community/flock/kmapper/compiler/fir/KMapperFirMappingChecker.kt
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Original file line number Diff line number Diff line change
Expand Up @@ -162,7 +162,8 @@ class KMapperFirMappingChecker(val collector: MessageCollector, private val sess
return resolvedTypeArgument?.resolveConstructorFields()
}

private fun ConeKotlinType.resolveConstructorFields(): List<Field> {
private fun ConeKotlinType.resolveConstructorFields(visited: MutableSet<ConeKotlinType> = mutableSetOf()): List<Field> {
if (!visited.add(this)) return emptyList()
val classSymbol = toRegularClassSymbol(session)
if (classSymbol?.moduleData is FirBinaryDependenciesModuleData) return emptyList()
val primaryConstructor = classSymbol?.constructors(session)?.firstOrNull()
Expand All @@ -171,7 +172,7 @@ class KMapperFirMappingChecker(val collector: MessageCollector, private val sess
name = parameter.name,
type = parameter.resolvedReturnType,
hasDefaultValue = parameter.hasDefaultValue,
fields = parameter.resolvedReturnType.resolveConstructorFields()
fields = parameter.resolvedReturnType.resolveConstructorFields(visited)
)
}.orEmpty()
}
Expand All @@ -181,7 +182,8 @@ class KMapperFirMappingChecker(val collector: MessageCollector, private val sess
return resolvedTypeArgument?.resolvePropertyFields()
}

private fun ConeKotlinType.resolvePropertyFields(): List<Field> {
private fun ConeKotlinType.resolvePropertyFields(visited: MutableSet<ConeKotlinType> = mutableSetOf()): List<Field> {
if (!visited.add(this)) return emptyList()
val classSymbol = toRegularClassSymbol(session)
return classSymbol?.declaredProperties(session)
.orEmpty()
Expand All @@ -190,7 +192,7 @@ class KMapperFirMappingChecker(val collector: MessageCollector, private val sess
name = property.name,
type = property.resolvedReturnType,
hasDefaultValue = property.resolvedDefaultValue != null,
fields = property.resolvedReturnType.resolvePropertyFields()
fields = property.resolvedReturnType.resolvePropertyFields(visited)
)
}
}
Expand Down
25 changes: 22 additions & 3 deletions ...plugin/src/main/kotlin/community/flock/kmapper/compiler/ir/KMapperIrBuildMapperVisitor.kt
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Original file line number Diff line number Diff line change
Expand Up @@ -119,14 +119,33 @@ class KMapperIrBuildMapperVisitor(
val fromTypeArgument = expression.typeArguments[1] ?: error("Could not resolve source type for mapper")

val remapper = object : IrElementTransformerVoid() {
// The mapper lambda has two parameters:
// 1. Extension receiver ($this$mapper): the TO type being constructed
// 2. Regular parameter (it): the FROM source instance
// When extracting value expressions from the lambda body, we need to remap
// both parameters. The FROM parameter (it) is replaced with the actual receiver.
// The TO parameter ($this$mapper) may be captured in nested lambda closures
// even if not explicitly used; we must also remap it to avoid dangling references
// after the lambda is removed from the IR tree.
val itParamSymbol = callArgument?.function?.parameters
?.firstOrNull { it.kind == IrParameterKind.Regular || it.kind == IrParameterKind.Context }
?.symbol
val thisParamSymbol = callArgument?.function?.parameters
?.firstOrNull { it.kind == IrParameterKind.ExtensionReceiver }
?.symbol

override fun visitGetValue(expression: IrGetValue): IrExpression {
val transformedGetValue = super.visitGetValue(expression)
val itParamSymbol = callArgument?.function?.parameters
?.firstOrNull { it.kind == IrParameterKind.Regular || it.kind == IrParameterKind.Context }
?.symbol
if (expression.symbol == itParamSymbol) {
return receiverArgument.deepCopyWithSymbols()
}
// The TO extension receiver ($this$mapper) may be captured by nested lambdas.
// Since the TO object is being constructed (not yet available), we replace
// references with the receiver argument. This is safe because the captured
// reference is never actually accessed at runtime — only present in the closure.
if (expression.symbol == thisParamSymbol) {
return receiverArgument.deepCopyWithSymbols()
}
return transformedGetValue
}
}
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166 changes: 166 additions & 0 deletions test-integration/src/test/kotlin/community/flock/kmapper/BasicMappingTest.kt
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Expand Up @@ -642,6 +642,172 @@ class BasicMappingTest {
}
}

@Test
fun shouldCompile_valueClassAutoMapInDslBlock() {
IntegrationTest(options)
.file("App.kt") {
$$"""
|package sample
|
|import community.flock.kmapper.mapper
|
|@JvmInline
|value class ModelId(val value: String)
|@JvmInline
|value class TaskDesc(val value: String)
|
|data class Run(
| val id: String,
| val modelIdentifier: ModelId,
| val taskDescription: TaskDesc,
| val isViewed: Boolean,
|)
|
|data class RunDto(
| val id: String,
| val modelIdentifier: String,
| val taskDescription: String,
| val isViewed: Boolean,
|)
|
|fun Run.toDto(): RunDto = mapper {
| isViewed = it.isViewed
|}
|
|fun main() {
| val run = Run(id = "1", modelIdentifier = ModelId("gpt-4"), taskDescription = TaskDesc("do stuff"), isViewed = true)
| val dto = run.toDto()
| println(dto)
|}
|
""".trimMargin()
}
.compileSuccess { output ->
assertTrue(
output.contains("RunDto(id=1, modelIdentifier=gpt-4, taskDescription=do stuff, isViewed=true)"),
"Expected RunDto(id=1, modelIdentifier=gpt-4, taskDescription=do stuff, isViewed=true) in output but got: $output"
)
}
}

@Test
fun shouldCompile_valueClassAutoMapInDslBlockWithSerializable() {
IntegrationTest(
options.copy(
additionalPlugins = listOf("""kotlin("plugin.serialization") version "${options.kotlinVersion}""""),
additionalDependencies = listOf("org.jetbrains.kotlinx:kotlinx-serialization-json:1.8.1"),
)
)
.file("App.kt") {
$$"""
|package sample
|
|import community.flock.kmapper.mapper
|import kotlinx.serialization.Serializable
|import kotlinx.serialization.SerialName
|
|@JvmInline
|value class ModelId(val value: String)
|@JvmInline
|value class TaskDesc(val value: String)
|
|data class Run(
| val id: String,
| val modelIdentifier: ModelId,
| val taskDescription: TaskDesc,
| val isViewed: Boolean,
|)
|
|@Serializable
|@SerialName("RunDto")
|data class RunDto(
| val id: String,
| val modelIdentifier: String,
| val taskDescription: String,
| val isViewed: Boolean,
|)
|
|fun Run.toDto(): RunDto = mapper {
| isViewed = it.isViewed
|}
|
|fun main() {
| val run = Run(id = "1", modelIdentifier = ModelId("gpt-4"), taskDescription = TaskDesc("do stuff"), isViewed = true)
| val dto = run.toDto()
| println(dto)
|}
|
""".trimMargin()
}
.compileSuccess { output ->
assertTrue(
output.contains("RunDto(id=1, modelIdentifier=gpt-4, taskDescription=do stuff, isViewed=true)"),
"Expected RunDto(id=1, modelIdentifier=gpt-4, taskDescription=do stuff, isViewed=true) in output but got: $output"
)
}
}

@Test
fun shouldCompile_selfReferencingType() {
IntegrationTest(options)
.file("App.kt") {
$$"""
|package sample
|
|import community.flock.kmapper.mapper
|
|data class Category(val name: String, val parent: Category?)
|data class CategoryDto(val name: String, val parent: Category?)
|
|fun main() {
| val category = Category("child", Category("root", null))
| val dto: CategoryDto = category.mapper()
| println(dto)
|}
|
""".trimMargin()
}
.compileSuccess { output ->
assertTrue(
output.contains("CategoryDto(name=child, parent=Category(name=root, parent=null))"),
"Expected CategoryDto(name=child, parent=Category(name=root, parent=null)) in output"
)
}
}

@Test
fun shouldCompile_nestedLambdaInMapperBlock() {
IntegrationTest(options)
.file("App.kt") {
$$"""
|package sample
|
|import community.flock.kmapper.mapper
|
|data class User(val firstName: String, val tags: List<String>)
|data class UserDto(val name: String, val tags: List<String>)
|
|fun User.toDto(): UserDto = mapper {
| name = it.firstName
| tags = it.tags.map { tag -> tag.uppercase() }
|}
|
|fun main() {
| val user = User("Alice", listOf("kotlin", "java"))
| val dto = user.toDto()
| println(dto)
|}
|
""".trimMargin()
}
.compileSuccess { output ->
assertTrue(
output.contains("UserDto(name=Alice, tags=[KOTLIN, JAVA])"),
"Expected UserDto(name=Alice, tags=[KOTLIN, JAVA]) in output"
)
}
}

@Test
fun shouldFail_missingParameterAge() {
IntegrationTest(options)
Expand Down
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