Fix serialization of referentially equal objects.

Fix #50

Author: konsoletyper

json/src/main/java/org/teavm/flavour/json/emit/JsonSerializerEmitter.java

@@ -186,6 +186,9 @@ private Value<JsonSerializer> emitClassSerializer(ReflectClass<?> cls) {
                 emitIdentity(information, value, context, target);
                 emitProperties(information, value, context, target);
                 Value<? extends Node> result = emitInheritance(information, target);
+                if (information.idGenerator == IdGeneratorType.NONE) {
+                    emit(() -> context.get().release(value.get()));
+                }
                 exit(() -> result.get());
             });
         }
@@ -217,7 +220,7 @@ private void emitIdentity(ClassInformation information, Value<Object> value,
             Value<JsonSerializerContext> context, Value<ObjectNode> target) {
         switch (information.idGenerator) {
             case NONE:
-                emit(() -> context.get().touch(value.get()));
+                emit(() -> context.get().lock(value.get()));
                 break;
             case INTEGER:
                 emitIntegerIdentity(information, value, context, target);

json/src/main/java/org/teavm/flavour/json/serializer/JsonSerializerContext.java

@@ -23,7 +23,7 @@
 public class JsonSerializerContext {
     private int lastId;
     private Map<Object, Integer> ids = new IdentityHashMap<>();
-    private Set<Object> touchedObjects = Collections.newSetFromMap(new IdentityHashMap<>());
+    private Set<Object> lockedObjects = Collections.newSetFromMap(new IdentityHashMap<>());
 
     public boolean hasId(Object object) {
         return ids.containsKey(object);
@@ -38,10 +38,14 @@ public int getId(Object object) {
         return id;
     }
 
-    public void touch(Object object) {
-        if (touchedObjects.contains(object)) {
+    public void lock(Object object) {
+        if (lockedObjects.contains(object)) {
             throw new IllegalArgumentException("Object has already been serialized: " + object);
         }
-        touchedObjects.add(object);
+        lockedObjects.add(object);
+    }
+
+    public void release(Object object) {
+        lockedObjects.remove(object);
     }
 }

json/src/test/java/org/teavm/flavour/json/test/SerializerTest.java

@@ -37,6 +37,7 @@
 import com.fasterxml.jackson.databind.JsonNode;
 import com.fasterxml.jackson.databind.node.ArrayNode;
 import com.fasterxml.jackson.databind.node.NullNode;
+import com.fasterxml.jackson.databind.node.NumericNode;
 import java.math.BigDecimal;
 import java.math.BigInteger;
 import java.util.ArrayList;
@@ -484,6 +485,18 @@ public void abstractSuperclass() {
         assertEquals("Unexpected root[1].baz", 4, node.get(1).get("baz").asInt());
     }
 
+    @Test
+    public void sameObjectInArray() {
+        A a = new A();
+        A[] array = { a, a };
+        JsonNode node = JSONRunner.serialize(array);
+        assertEquals(2, node.size());
+        assertTrue(node.get(0).get("a") instanceof NullNode);
+        assertTrue(node.get(1).get("a") instanceof NullNode);
+        assertEquals(0, node.get(0).get("b").intValue());
+        assertEquals(0, node.get(1).get("b").intValue());
+    }
+
     @JsonPersistable
     public static class A {
         private String a;