From 981db7fa04d3a2bf7cd1f5734b8d99907ab78118 Mon Sep 17 00:00:00 2001
From: Jason Zaugg <jzaugg@gmail.com>
Date: Mon, 4 Dec 2023 13:58:28 +1000
Subject: [PATCH] Fix regression in Map deserializtion in Scala 2.13 when
 default typing is enabled.

This Map serializer is implemented in terms of the Java version and is
somewhat fragile, as discussed in #643 / #470.

This commit ensures that the wrapper class is a member class in both Scala and Java.

That results in this JSON as the serializer code chooses not to put
the inner class name in the type annotation.

```
{"m":["scala.collection.immutable.Map",{"one":"one","two":"two"}]}
```

Fixes #643
---
 .../scala/ser/MapSerializerModule.scala       | 17 +++++++--
 .../DefaultTypingMapDeserializerTest.scala    | 35 +++++++++++++++++++
 2 files changed, 50 insertions(+), 2 deletions(-)
 create mode 100644 src/test/scala/com/fasterxml/jackson/module/scala/deser/DefaultTypingMapDeserializerTest.scala

diff --git a/src/main/scala/com/fasterxml/jackson/module/scala/ser/MapSerializerModule.scala b/src/main/scala/com/fasterxml/jackson/module/scala/ser/MapSerializerModule.scala
index 773076ea..a81cd363 100644
--- a/src/main/scala/com/fasterxml/jackson/module/scala/ser/MapSerializerModule.scala
+++ b/src/main/scala/com/fasterxml/jackson/module/scala/ser/MapSerializerModule.scala
@@ -8,20 +8,33 @@ import com.fasterxml.jackson.databind.ser.std.StdDelegatingSerializer
 import com.fasterxml.jackson.databind.util.StdConverter
 import com.fasterxml.jackson.module.scala.modifiers.MapTypeModifierModule
 
+import java.util
 import scala.collection.JavaConverters._
 import scala.collection.Map
 
 private class MapConverter(inputType: JavaType, config: SerializationConfig)
   extends StdConverter[Map[_,_],java.util.Map[_,_]]
 {
+  // Making this an inner class avoids deserializaion errors when polymorphic typing
+  // is enabled. In Scala 2.12 `delegate.asJava` happened to be an inner class but
+  // this implementation detail changed in 2.13.
+  //
+  // Tested in DefaultTypingMapDeserializerTest
+  private class MapWrapper[A, B](delegate: Map[A, B]) extends util.AbstractMap[A, B] {
+    private val wrapped = delegate.asJava
+
+    override def entrySet(): util.Set[util.Map.Entry[A, B]] = wrapped.entrySet()
+  }
+
   def convert(value: Map[_,_]): java.util.Map[_,_] = {
     val m = if (config.isEnabled(SerializationFeature.WRITE_NULL_MAP_VALUES)) {
       value
     } else {
       value.filter(_._2 != None)
     }
-    m.asJava
-  }
+    new MapWrapper(m)
+//    m.asJava
+  }``
 
 
   override def getInputType(factory: TypeFactory) = inputType
diff --git a/src/test/scala/com/fasterxml/jackson/module/scala/deser/DefaultTypingMapDeserializerTest.scala b/src/test/scala/com/fasterxml/jackson/module/scala/deser/DefaultTypingMapDeserializerTest.scala
new file mode 100644
index 00000000..057ffe35
--- /dev/null
+++ b/src/test/scala/com/fasterxml/jackson/module/scala/deser/DefaultTypingMapDeserializerTest.scala
@@ -0,0 +1,35 @@
+package com.fasterxml.jackson.module.scala.deser
+
+import com.fasterxml.jackson.databind.ObjectMapper
+import com.fasterxml.jackson.module.scala.DefaultScalaModule
+
+import scala.collection.immutable
+
+class DefaultTypingMapDeserializerTest extends DeserializerTest {
+
+  def module: DefaultScalaModule.type = DefaultScalaModule
+
+  override def newMapper: ObjectMapper = {
+    val mapper = super.newMapper
+    mapper.activateDefaultTyping(mapper.getPolymorphicTypeValidator)
+  }
+
+  "Scala Module" should "deserialize immutable Map when default typing enabled" in {
+    val map = HasMap(immutable.Map("one" -> "one", "two" -> "two"))
+
+    val mapper = newMapper
+
+    val json = mapper.writeValueAsString(map)
+    // Was failing in Scala 2.13+ with:
+    // > Could not resolve type id 'scala.collection.convert.JavaCollectionWrappers$MapWrapper' as a subtype of
+    // > `scala.collection.immutable.Map<java.lang.String,java.lang.String>`: Not a subtype
+    //
+    // prior the changing MapSerializerModule.scala to use an inner class for MapWrapper
+    val read = mapper.readValue(json, classOf[HasMap])
+
+    read shouldEqual map
+  }
+
+}
+
+case class HasMap(m: Map[String, String])