Fix #1829: change JsonNode.deepCopy() return type to safer (#4832)

release-notes/VERSION

@@ -22,6 +22,8 @@ Versions: 3.x (for earlier see VERSION-2.x)
  (reported by timo-schmid@github)
 #1789: Add `createGenerator` methods in `ObjectMapper`, `ObjectWriter`
 #1790: Add `createParser` methods in `ObjectMapper`, `ObjectReader`
+#1829: `JsonNode.deepCopy() `ClassCastException`s
+ (reported by @D3v01dZA)
 #1883: Add "abstract type mapping" for deserialization from `Map<ENUMTYPE,V>`
   into `EnumMap` (and `Set<ENUMTYPE>` to `EnumSet<EnumType>`) 
 #1888: Merge `ResolvableSerializer` into `JsonSerializer`, `ResolvableDeserializer`

src/main/java/tools/jackson/databind/JsonNode.java

@@ -102,7 +102,7 @@ protected JsonNode() { }
      * @return Node that is either a copy of this node (and all non-leaf
      *    children); or, for immutable leaf nodes, node itself.
      */
-    public abstract <T extends JsonNode> T deepCopy();
+    public abstract JsonNode deepCopy();
 
     /*
     /**********************************************************************

src/main/java/tools/jackson/databind/deser/jdk/JDKFromStringDeserializer.java

@@ -267,6 +267,7 @@ protected int _firstHyphenOrUnderscore(String str)
         return -1;
     }
 
+    @SuppressWarnings("deprecation") // Locale constructors deprecated in JDK 19
     private Locale _deserializeLocale(String fullValue, DeserializationContext ctxt)
         throws JacksonException
     {

src/main/java/tools/jackson/databind/node/ArrayNode.java

@@ -47,7 +47,6 @@ protected JsonNode _at(JsonPointer ptr) {
     }
 
     // note: co-variant to allow caller-side type safety
-    @SuppressWarnings("unchecked")
     @Override
     public ArrayNode deepCopy()
     {

src/main/java/tools/jackson/databind/node/BooleanNode.java

@@ -53,6 +53,9 @@ public JsonNodeType getNodeType() {
         return _value ? JsonToken.VALUE_TRUE : JsonToken.VALUE_FALSE;
     }
 
+    @Override
+    public BooleanNode deepCopy() { return this; }
+
     @Override
     public boolean booleanValue() {
         return _value;

src/main/java/tools/jackson/databind/node/MissingNode.java

@@ -34,9 +34,8 @@ protected Object readResolve() {
     }
 
     // Immutable: no need to copy
-    @SuppressWarnings("unchecked")
     @Override
-    public <T extends JsonNode> T deepCopy() { return (T) this; }
+    public MissingNode deepCopy() { return this; }
 
     public static MissingNode getInstance() { return instance; }
 

src/main/java/tools/jackson/databind/node/NullNode.java

@@ -33,6 +33,9 @@ public JsonNodeType getNodeType() {
 
     @Override public JsonToken asToken() { return JsonToken.VALUE_NULL; }
 
+    @Override
+    public NullNode deepCopy() { return this; }
+
     @Override
     public String asText(String defaultValue) { return defaultValue; }
 

src/main/java/tools/jackson/databind/node/NumericNode.java

@@ -21,6 +21,10 @@ public final JsonNodeType getNodeType()
         return JsonNodeType.NUMBER;
     }
 
+    // Overridden for type co-variance
+    @Override
+    public NumericNode deepCopy() { return this; }
+
     // // // Let's re-abstract so sub-classes handle them
 
     @Override

src/main/java/tools/jackson/databind/node/ObjectNode.java

@@ -45,7 +45,6 @@ protected JsonNode _at(JsonPointer ptr) {
      * have to, as long as sub-types override the method but...
      */
     // note: co-variant for type safety
-    @SuppressWarnings("unchecked")
     @Override
     public ObjectNode deepCopy()
     {

src/main/java/tools/jackson/databind/node/TextNode.java

@@ -52,6 +52,9 @@ public JsonNodeType getNodeType() {
 
     @Override public JsonToken asToken() { return JsonToken.VALUE_STRING; }
 
+    @Override
+    public TextNode deepCopy() { return this; }
+
     @Override
     public String textValue() {
         return _value;

src/main/java/tools/jackson/databind/node/ValueNode.java

@@ -33,9 +33,8 @@ protected JsonNode _at(JsonPointer ptr) {
      * All current value nodes are immutable, so we can just return
      * them as is.
      */
-    @SuppressWarnings("unchecked")
     @Override
-    public <T extends JsonNode> T deepCopy() { return (T) this; }
+    public ValueNode deepCopy() { return this; }
 
     @Override public abstract JsonToken asToken();
 

src/test/java/tools/jackson/databind/ObjectReaderTest.java

@@ -554,9 +554,8 @@ public void serializeWithType(JsonGenerator g, SerializationContext ctxt, TypeSe
         }
 
         @Override
-        @SuppressWarnings("unchecked")
-        public <T extends JsonNode> T deepCopy() {
-            return (T) new CustomObjectNode(_delegate);
+        public CustomObjectNode deepCopy() {
+            return new CustomObjectNode(_delegate);
         }
 
         @Override
@@ -675,9 +674,8 @@ public void serializeWithType(JsonGenerator g, SerializationContext ctxt, TypeSe
         }
 
         @Override
-        @SuppressWarnings("unchecked")
-        public <T extends JsonNode> T deepCopy() {
-            return (T) new DelegatingArrayNode(_delegate);
+        public DelegatingArrayNode deepCopy() {
+            return new DelegatingArrayNode(_delegate);
         }
 
         @Override

src/test/java/tools/jackson/databind/deser/jdk/LocaleDeserTest.java

@@ -15,7 +15,9 @@
 import static tools.jackson.databind.testutil.DatabindTestUtil.newJsonMapper;
 import static tools.jackson.databind.testutil.DatabindTestUtil.q;
 
-// Tests for `java.util.Locale`
+// Tests for `java.util.Locale`.
+// NOTE: warnings are due to JDK 19 deprecating Locale constructors
+@SuppressWarnings("deprecation")
 public class LocaleDeserTest
 {
     private final Locale[] LOCALES = new Locale[]

src/test/java/tools/jackson/databind/misc/CaseInsensitiveDeser953Test.java

@@ -18,13 +18,15 @@ static class Id953 {
         public int someId;
     }
 
+    @SuppressWarnings("deprecation") // Locale constructors deprecated in JDK 19
     private final Locale LOCALE_EN = new Locale("en", "US");
 
     private final ObjectMapper INSENSITIVE_MAPPER_EN = jsonMapperBuilder()
             .enable(MapperFeature.ACCEPT_CASE_INSENSITIVE_PROPERTIES)
             .defaultLocale(LOCALE_EN)
             .build();
 
+    @SuppressWarnings("deprecation") // Locale constructors deprecated in JDK 19
     private final Locale LOCALE_TR = new Locale("tr", "TR");
 
     private final ObjectMapper INSENSITIVE_MAPPER_TR = jsonMapperBuilder()

src/test/java/tools/jackson/databind/ser/jdk/JDKTypeSerializationTest.java

@@ -95,6 +95,7 @@ public void testCurrency() throws IOException
         assertEquals(q("USD"), MAPPER.writeValueAsString(usd));
     }
 
+    @SuppressWarnings("deprecation")
     @Test
     public void testLocale() throws IOException
     {