Fix #2457 (enum subtypes not working as map keys)

Author: cowtowncoder

release-notes/CREDITS-2.x

@@ -971,3 +971,7 @@ Martín Coll (colltoaction@github)
   * Contributed #2467: Accept `JsonTypeInfo.As.WRAPPER_ARRAY` with no second argument to
    deserialize as "null value"
   (2.10.0)
+
+Andrey Kulikov (ankulikov@github)
+  * Reported #2457: Extended enum values are not handled as enums when used as Map keys
+  (2.10.1)

release-notes/VERSION-2.x

@@ -4,6 +4,11 @@ Project: jackson-databind
 === Releases === 
 ------------------------------------------------------------------------
 
+2.10.1 (not yet released)
+
+#2457: Extended enum values are not handled as enums when used as Map keys
+ (reported by Andrey K)
+
 2.10.0 (26-Sep-2019)
 
 #18: Make `JsonNode` serializable

src/main/java/com/fasterxml/jackson/databind/JavaType.java

@@ -288,7 +288,12 @@ public boolean isConcrete() {
     public boolean isArrayType() { return false; }
 
     @Override
-    public final boolean isEnumType() { return _class.isEnum(); }
+    public final boolean isEnumType() {
+        // 29-Sep-2019, tatu: `Class.isEnum()` not enough to detect custom subtypes,
+        //    use this instead
+//        return Enum.class.isAssignableFrom(_class);
+        return _class.isEnum();
+    }
 
     @Override
     public final boolean isInterface() { return _class.isInterface(); }

src/main/java/com/fasterxml/jackson/databind/ser/std/StdKeySerializers.java

@@ -98,7 +98,9 @@ public static JsonSerializer<Object> getFallbackKeySerializer(SerializationConfi
             if (rawKeyType == Enum.class) {
                 return new Dynamic();
             }
-            if (rawKeyType.isEnum()) {
+            // 29-Sep-2019, tatu: [databind#2457] can not use 'rawKeyType.isEnum()`, won't work
+            //    for subtypes.
+            if (Enum.class.isAssignableFrom(rawKeyType)) {
                 return EnumKeySerializer.construct(rawKeyType,
                         EnumValues.constructFromName(config, (Class<Enum<?>>) rawKeyType));
             }

src/test/java/com/fasterxml/jackson/databind/deser/jdk/EnumMapDeserializationTest.java

@@ -1,6 +1,7 @@
 package com.fasterxml.jackson.databind.deser.jdk;
 
 import java.util.EnumMap;
+import java.util.LinkedHashMap;
 import java.util.Map;
 
 import com.fasterxml.jackson.annotation.*;
@@ -77,6 +78,22 @@ public Pojo1859(EnumMap<Enum1859, String> v) {
         }
     }
 
+    // [databind#2457]
+    enum MyEnum2457 {
+        A,
+        B() {
+            // just to ensure subclass construction
+            @Override
+            public void foo() { }
+        };
+
+        // needed to force subclassing
+        public void foo() { }
+
+        @Override
+        public String toString() { return name() + " as string"; }
+    }
+
     /*
     /**********************************************************
     /* Test methods, basic
@@ -224,4 +241,21 @@ public void testUnknownKeyAsNull() throws Exception
         assertEquals(1, value2.size());
         assertEquals("value", value2.get(null));
     }
+
+    // [databind#2457]
+    public void testCustomEnumAsRootMapKey() throws Exception
+    {
+        final ObjectMapper mapper = newJsonMapper();
+        final Map<MyEnum2457, String> map = new LinkedHashMap<>();
+        map.put(MyEnum2457.A, "1");
+        map.put(MyEnum2457.B, "2");
+        assertEquals(aposToQuotes("{'A':'1','B':'2'}"),
+                mapper.writeValueAsString(map));
+
+        // But should be able to override
+        assertEquals(aposToQuotes("{'"+MyEnum2457.A.toString()+"':'1','"+MyEnum2457.B.toString()+"':'2'}"),
+                mapper.writer()
+                    .with(SerializationFeature.WRITE_ENUMS_USING_TO_STRING)
+                    .writeValueAsString(map));
+    }
 }