Add synthetic companion with .serializer() getter even if default serializer is overridden. (kotlinx.serialization/228)

plugins/kotlin-serialization/kotlin-serialization-compiler/src/org/jetbrains/kotlinx/serialization/compiler/backend/common/SerializableCompanionCodegen.kt

@@ -16,6 +16,7 @@
 
 package org.jetbrains.kotlinx.serialization.compiler.backend.common
 
+import org.jetbrains.kotlin.descriptors.CallableMemberDescriptor
 import org.jetbrains.kotlin.descriptors.ClassDescriptor
 import org.jetbrains.kotlin.descriptors.FunctionDescriptor
 import org.jetbrains.kotlin.incremental.components.NoLookupLocation
@@ -34,10 +35,15 @@ abstract class SerializableCompanionCodegen(
         val serializerGetterDescriptor = companionDescriptor.unsubstitutedMemberScope.getContributedFunctions(
             SERIALIZER_PROVIDER_NAME,
             NoLookupLocation.FROM_BACKEND
-        ).first { func ->
+        ).firstOrNull {
-            func.valueParameters.size == serializableDescriptor.declaredTypeParameters.size &&
+            it.valueParameters.size == serializableDescriptor.declaredTypeParameters.size
-                    func.valueParameters.all { isKSerializer(it.type) }
+                    && it.kind == CallableMemberDescriptor.Kind.SYNTHESIZED
-        }
+                    && it.valueParameters.all { p -> isKSerializer(p.type) }
+                    && it.returnType != null && isKSerializer(it.returnType)
+        } ?: throw IllegalStateException(
+            "Can't find synthesized 'Companion.serializer()' function to generate, " +
+                    "probably clash with user-defined function has occurred"
+        )
         generateSerializerGetter(serializerGetterDescriptor)
     }
 

plugins/kotlin-serialization/kotlin-serialization-compiler/src/org/jetbrains/kotlinx/serialization/compiler/backend/ir/SerializableCompanionIrGenerator.kt

@@ -13,7 +13,6 @@ import org.jetbrains.kotlin.resolve.BindingContext
 import org.jetbrains.kotlin.resolve.descriptorUtil.module
 import org.jetbrains.kotlinx.serialization.compiler.backend.common.SerializableCompanionCodegen
 import org.jetbrains.kotlinx.serialization.compiler.resolve.*
-import org.jetbrains.kotlinx.serialization.compiler.resolve.KSerializerDescriptorResolver.findSerializerConstructorForTypeArgumentsSerializers
 
 class SerializableCompanionIrGenerator(
     val irClass: IrClass,
@@ -33,7 +32,7 @@ class SerializableCompanionIrGenerator(
         ) {
             val companionDescriptor = irClass.descriptor
             val serializableClass = getSerializableClassDescriptorByCompanion(companionDescriptor) ?: return
-            if (serializableClass.isInternalSerializable)
+            if (serializableClass.shouldHaveGeneratedMethodsInCompanion)
                 SerializableCompanionIrGenerator(irClass, context, bindingContext).generate()
         }
     }

plugins/kotlin-serialization/kotlin-serialization-compiler/src/org/jetbrains/kotlinx/serialization/compiler/backend/js/SerializableCompanionJsTranslator.kt

@@ -56,7 +56,7 @@ class SerializableCompanionJsTranslator(
     companion object {
         fun translate(declaration: KtPureClassOrObject, descriptor: ClassDescriptor, translator: DeclarationBodyVisitor, context: TranslationContext) {
             val serializableClass = getSerializableClassDescriptorByCompanion(descriptor) ?: return
-            if (serializableClass.isInternalSerializable)
+            if (serializableClass.shouldHaveGeneratedMethodsInCompanion)
                 SerializableCompanionJsTranslator(descriptor, translator, context).generate()
         }
     }

plugins/kotlin-serialization/kotlin-serialization-compiler/src/org/jetbrains/kotlinx/serialization/compiler/backend/jvm/SerializableCompanionCodegenImpl.kt

@@ -18,10 +18,12 @@ package org.jetbrains.kotlinx.serialization.compiler.backend.jvm
 
 import org.jetbrains.kotlin.codegen.ImplementationBodyCodegen
 import org.jetbrains.kotlin.descriptors.FunctionDescriptor
-import org.jetbrains.kotlin.resolve.BindingContext
 import org.jetbrains.kotlin.resolve.descriptorUtil.module
 import org.jetbrains.kotlinx.serialization.compiler.backend.common.SerializableCompanionCodegen
-import org.jetbrains.kotlinx.serialization.compiler.resolve.*
+import org.jetbrains.kotlinx.serialization.compiler.resolve.classSerializer
+import org.jetbrains.kotlinx.serialization.compiler.resolve.getSerializableClassDescriptorByCompanion
+import org.jetbrains.kotlinx.serialization.compiler.resolve.shouldHaveGeneratedMethodsInCompanion
+import org.jetbrains.kotlinx.serialization.compiler.resolve.toClassDescriptor
 
 class SerializableCompanionCodegenImpl(private val codegen: ImplementationBodyCodegen) :
         SerializableCompanionCodegen(codegen.descriptor, codegen.bindingContext) {
@@ -29,7 +31,7 @@ class SerializableCompanionCodegenImpl(private val codegen: ImplementationBodyCo
     companion object {
         fun generateSerializableExtensions(codegen: ImplementationBodyCodegen) {
             val serializableClass = getSerializableClassDescriptorByCompanion(codegen.descriptor) ?: return
-            if (serializableClass.isInternalSerializable)
+            if (serializableClass.shouldHaveGeneratedMethodsInCompanion)
                 SerializableCompanionCodegenImpl(codegen).generate()
         }
     }

plugins/kotlin-serialization/kotlin-serialization-compiler/src/org/jetbrains/kotlinx/serialization/compiler/extensions/SerializationResolveExtension.kt

@@ -61,7 +61,7 @@ open class SerializationResolveExtension : SyntheticResolveExtension {
     }
 
     override fun getSyntheticCompanionObjectNameIfNeeded(thisDescriptor: ClassDescriptor): Name? =
-        if (thisDescriptor.isInternalSerializable) SpecialNames.DEFAULT_NAME_FOR_COMPANION_OBJECT
+        if (thisDescriptor.shouldHaveGeneratedMethodsInCompanion) SpecialNames.DEFAULT_NAME_FOR_COMPANION_OBJECT
         else null
 
     override fun addSyntheticSupertypes(thisDescriptor: ClassDescriptor, supertypes: MutableList<KotlinType>) {

plugins/kotlin-serialization/kotlin-serialization-compiler/src/org/jetbrains/kotlinx/serialization/compiler/resolve/KSerializationUtil.kt

@@ -97,6 +97,8 @@ val KotlinType?.toClassDescriptor: ClassDescriptor?
     @JvmName("toClassDescriptor")
     get() = this?.constructor?.declarationDescriptor as? ClassDescriptor
 
+internal val ClassDescriptor.shouldHaveGeneratedMethodsInCompanion: Boolean
+    get() = this.kind == ClassKind.CLASS && annotations.hasAnnotation(SerializationAnnotations.serializableAnnotationFqName)
 
 val ClassDescriptor.isInternalSerializable: Boolean //todo normal checking
     get() {
@@ -159,7 +161,7 @@ val KotlinType.genericIndex: Int?
 fun getSerializableClassDescriptorByCompanion(thisDescriptor: ClassDescriptor): ClassDescriptor? {
     if (!thisDescriptor.isCompanionObject) return null
     val classDescriptor = (thisDescriptor.containingDeclaration as? ClassDescriptor) ?: return null
-    if (!classDescriptor.isInternalSerializable) return null
+    if (!classDescriptor.shouldHaveGeneratedMethodsInCompanion) return null
     return classDescriptor
 }