Unify Polymorphic and Sealed class serializers check:

now it is allowed to have a conflicting name on deserialization, conflicts are reported only during encoding.

Author: sandwwraith

formats/json-tests/commonTest/src/kotlinx/serialization/features/JsonClassDiscriminatorTest.kt

@@ -8,6 +8,7 @@ import kotlinx.serialization.*
 import kotlinx.serialization.builtins.*
 import kotlinx.serialization.json.*
 import kotlinx.serialization.modules.*
+import kotlinx.serialization.test.assertFailsWithMessage
 import kotlin.test.*
 
 class JsonClassDiscriminatorTest : JsonTestBase() {
@@ -110,4 +111,21 @@ class JsonClassDiscriminatorTest : JsonTestBase() {
             json
         )
     }
+
+    @Serializable
+    @JsonClassDiscriminator("type2")
+    @SerialName("Foo")
+    sealed interface Foo
+
+    @Serializable
+    @SerialName("FooImpl")
+    data class FooImpl(val type2: String) : Foo
+
+    @Test
+    fun testCannotHaveConflictWithJsonClassDiscriminator() {
+        assertFailsWithMessage<SerializationException>("Class 'FooImpl' cannot be serialized as base class 'Foo' because it has property name that conflicts with JSON class discriminator 'type2'") {
+            Json.encodeToString<Foo>( FooImpl("foo"))
+        }
+    }
+
 }

formats/json-tests/commonTest/src/kotlinx/serialization/modules/SerialNameCollisionTest.kt

@@ -6,6 +6,7 @@ package kotlinx.serialization.modules
 
 import kotlinx.serialization.*
 import kotlinx.serialization.json.*
+import kotlinx.serialization.test.assertFailsWithMessage
 import kotlin.test.*
 
 private const val prefix = "kotlinx.serialization.modules.SerialNameCollisionTest"
@@ -34,7 +35,6 @@ class SerialNameCollisionTest {
         classDiscriminator = discriminator
         this.useArrayPolymorphism = useArrayPolymorphism
         serializersModule = context
-
     }
 
     @Test
@@ -45,9 +45,15 @@ class SerialNameCollisionTest {
             }
         }
 
-        assertFailsWith<IllegalArgumentException> { Json("type", module) }
-        assertFailsWith<IllegalArgumentException> { Json("type2", module) }
-        Json("type3", module) // OK
+        assertFailsWithMessage<SerializationException>("Class 'kotlinx.serialization.modules.SerialNameCollisionTest.Derived' cannot be serialized as base class 'kotlinx.serialization.Polymorphic<Base>' because it has property name that conflicts with JSON class discriminator 'type'.") {
+            Json("type", module).encodeToString<Base>(Derived("foo", "bar"))
+        }
+        assertFailsWithMessage<SerializationException>("Class 'kotlinx.serialization.modules.SerialNameCollisionTest.Derived' cannot be serialized as base class 'kotlinx.serialization.Polymorphic<Base>' because it has property name that conflicts with JSON class discriminator 'type2'.") {
+            Json("type2", module).encodeToString<Base>(Derived("foo", "bar"))
+        }
+        assertEquals("{\"type3\":\"kotlinx.serialization.modules.SerialNameCollisionTest.Derived\",\"type\":\"foo\",\"type2\":\"bar\"}",
+            Json("type3", module).encodeToString<Base>(Derived("foo", "bar"))
+        )
     }
 
     @Test
@@ -68,10 +74,18 @@ class SerialNameCollisionTest {
             }
         }
 
-        assertFailsWith<IllegalArgumentException> { Json("type", module) }
-        assertFailsWith<IllegalArgumentException> { Json("type2", module) }
-        assertFailsWith<IllegalArgumentException> { Json("t3", module) }
-        Json("t4", module) // OK
+        assertFailsWithMessage<SerializationException>("Class 'kotlinx.serialization.modules.SerialNameCollisionTest.DerivedCustomized' cannot be serialized as base class 'kotlinx.serialization.Polymorphic<Base>' because it has property name that conflicts with JSON class discriminator 'type'.") {
+            Json("type", module).encodeToString<Base>(DerivedCustomized("foo", "bar", "t3"))
+        }
+        assertFailsWithMessage<SerializationException>("Class 'kotlinx.serialization.modules.SerialNameCollisionTest.DerivedCustomized' cannot be serialized as base class 'kotlinx.serialization.Polymorphic<Base>' because it has property name that conflicts with JSON class discriminator 'type2'.") {
+            Json("type2", module).encodeToString<Base>(DerivedCustomized("foo", "bar", "t3"))
+        }
+        assertFailsWithMessage<SerializationException>("Class 'kotlinx.serialization.modules.SerialNameCollisionTest.DerivedCustomized' cannot be serialized as base class 'kotlinx.serialization.Polymorphic<Base>' because it has property name that conflicts with JSON class discriminator 't3'.") {
+            Json("t3", module).encodeToString<Base>(DerivedCustomized("foo", "bar", "t3"))
+        }
+        assertEquals("{\"t4\":\"kotlinx.serialization.modules.SerialNameCollisionTest.DerivedCustomized\",\"type\":\"foo\",\"type2\":\"bar\",\"t3\":\"t3\"}",
+        Json("t4", module).encodeToString<Base>(DerivedCustomized("foo", "bar", "t3"))
+        )
 
     }
 

formats/json/commonMain/src/kotlinx/serialization/json/internal/JsonSerializersModuleValidator.kt

@@ -15,7 +15,6 @@ internal class JsonSerializersModuleValidator(
     configuration: JsonConfiguration,
 ) : SerializersModuleCollector {
 
-    private val discriminator: String = configuration.classDiscriminator
     private val useArrayPolymorphism: Boolean = configuration.useArrayPolymorphism
     private val isDiscriminatorRequired = configuration.classDiscriminatorMode != ClassDiscriminatorMode.NONE
 
@@ -33,10 +32,6 @@ internal class JsonSerializersModuleValidator(
     ) {
         val descriptor = actualSerializer.descriptor
         checkKind(descriptor, actualClass)
-        if (!useArrayPolymorphism && isDiscriminatorRequired) {
-            // Collisions with "type" can happen only for JSON polymorphism
-            checkDiscriminatorCollisions(descriptor, actualClass)
-        }
     }
 
     private fun checkKind(descriptor: SerialDescriptor, actualClass: KClass<*>) {
@@ -62,23 +57,6 @@ internal class JsonSerializersModuleValidator(
         }
     }
 
-    private fun checkDiscriminatorCollisions(
-        descriptor: SerialDescriptor,
-        actualClass: KClass<*>
-    ) {
-        for (i in 0 until descriptor.elementsCount) {
-            val name = descriptor.getElementName(i)
-            if (name == discriminator) {
-                throw IllegalArgumentException(
-                    "Polymorphic serializer for $actualClass has property '$name' that conflicts " +
-                            "with JSON class discriminator. You can either change class discriminator in JsonConfiguration, " +
-                            "rename property with @SerialName annotation " +
-                            "or fall back to array polymorphism"
-                )
-            }
-        }
-    }
-
     override fun <Base : Any> polymorphicDefaultSerializer(
         baseClass: KClass<Base>,
         defaultSerializerProvider: (value: Base) -> SerializationStrategy<Base>?