1 files changed, 60 insertions, 0 deletions
diff --git a/formats/json-tests/commonTest/src/kotlinx/serialization/features/PolymorphicDeserializationErrorMessagesTest.kt b/formats/json-tests/commonTest/src/kotlinx/serialization/features/PolymorphicDeserializationErrorMessagesTest.kt
new file mode 100644
index 00000000..2b2f1f70
--- /dev/null
+++ b/formats/json-tests/commonTest/src/kotlinx/serialization/features/PolymorphicDeserializationErrorMessagesTest.kt
@@ -0,0 +1,60 @@
+/*
+ * Copyright 2017-2023 JetBrains s.r.o. Use of this source code is governed by the Apache 2.0 license.
+ */
+
+package kotlinx.serialization.features
+
+import kotlinx.serialization.*
+import kotlinx.serialization.json.*
+import kotlin.test.*
+
+class PolymorphicDeserializationErrorMessagesTest : JsonTestBase() {
+    @Serializable
+    class DummyData(@Polymorphic val a: Any)
+
+    @Serializable
+    class Holder(val d: DummyData)
+
+    // TODO: remove this after #2480 is merged
+    private fun checkSerializationException(action: () -> Unit, assertions: SerializationException.(String) -> Unit) {
+        val e = assertFailsWith(SerializationException::class, action)
+        assertNotNull(e.message)
+        e.assertions(e.message!!)
+    }
+
+    @Test
+    fun testNotRegisteredMessage() = parametrizedTest { mode ->
+        val input = """{"d":{"a":{"type":"my.Class", "value":42}}}"""
+        checkSerializationException({
+            default.decodeFromString<Holder>(input, mode)
+        }, { message ->
+            // ReaderJsonLexer.peekLeadingMatchingValue is not implemented, so first-key optimization is not working for streaming yet.
+            if (mode == JsonTestingMode.STREAMING)
+                assertContains(message, "Unexpected JSON token at offset 10: Serializer for subclass 'my.Class' is not found in the polymorphic scope of 'Any' at path: \$.d.a")
+            else
+                assertContains(message, "Serializer for subclass 'my.Class' is not found in the polymorphic scope of 'Any'")
+        })
+    }
+
+    @Test
+    fun testDiscriminatorMissingNoDefaultMessage() = parametrizedTest { mode ->
+        val input = """{"d":{"a":{"value":42}}}"""
+        checkSerializationException({
+            default.decodeFromString<Holder>(input, mode)
+        }, { message ->
+            // Always slow path when discriminator is missing, so no position and path
+            assertContains(message, "Class discriminator was missing and no default serializers were registered in the polymorphic scope of 'Any'")
+        })
+    }
+
+    @Test
+    fun testClassDiscriminatorIsNull() = parametrizedTest { mode ->
+        val input = """{"d":{"a":{"type":null, "value":42}}}"""
+        checkSerializationException({
+            default.decodeFromString<Holder>(input, mode)
+        }, { message ->
+            // Always slow path when discriminator is missing, so no position and path
+            assertContains(message, "Class discriminator was missing and no default serializers were registered in the polymorphic scope of 'Any'")
+        })
+    }
+}