Add MinimalGenerics and allow users to set a GenericStrategy

src/com/esotericsoftware/kryo/Kryo.java

@@ -92,6 +92,7 @@
 import com.esotericsoftware.kryo.util.IdentityMap;
 import com.esotericsoftware.kryo.util.IntArray;
 import com.esotericsoftware.kryo.util.MapReferenceResolver;
+import com.esotericsoftware.kryo.util.MinimalGenerics;
 import com.esotericsoftware.kryo.util.NoGenerics;
 import com.esotericsoftware.kryo.util.ObjectMap;
 import com.esotericsoftware.kryo.util.Util;
@@ -1291,7 +1292,36 @@ public Generics getGenerics () {
 	 * setting in order to be compatible.
 	 * @param optimizedGenerics whether to optimize generics (default is true) */
 	public void setOptimizedGenerics (boolean optimizedGenerics) {
-		generics = optimizedGenerics ? new DefaultGenerics(this) : NoGenerics.INSTANCE;
+		setGenericsStrategy(optimizedGenerics ? GenericsStrategy.DEFAULT : GenericsStrategy.NONE);
+	}
+
+	/** Sets a {@link GenericsStrategy}.
+	 * 
+	 * TODO JavaDoc
+	 * 
+	 * @param strategy the strategy for processing generics information */
+	public void setGenericsStrategy (GenericsStrategy strategy) {
+		this.generics = strategy.createInstance(this);
+	}
+
+	public enum GenericsStrategy {
+		DEFAULT {
+			public Generics createInstance (Kryo kryo) {
+				return new DefaultGenerics(kryo);
+			}
+		},
+		MINIMAL {
+			public Generics createInstance (Kryo kryo) {
+				return new MinimalGenerics(kryo);
+			}
+		},
+		NONE {
+			public Generics createInstance (Kryo kryo) {
+				return NoGenerics.INSTANCE;
+			}
+		};
+
+		public abstract Generics createInstance (Kryo kryo);
 	}
 
 	static final class DefaultSerializerEntry {

src/com/esotericsoftware/kryo/util/BaseGenerics.java

@@ -0,0 +1,93 @@
+/* Copyright (c) 2008-2022, Nathan Sweet
+ * All rights reserved.
+ * 
+ * Redistribution and use in source and binary forms, with or without modification, are permitted provided that the following
+ * conditions are met:
+ * 
+ * - Redistributions of source code must retain the above copyright notice, this list of conditions and the following disclaimer.
+ * - Redistributions in binary form must reproduce the above copyright notice, this list of conditions and the following
+ * disclaimer in the documentation and/or other materials provided with the distribution.
+ * - Neither the name of Esoteric Software nor the names of its contributors may be used to endorse or promote products derived
+ * from this software without specific prior written permission.
+ * 
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING,
+ * BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT
+ * SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+ * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
+ * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. */
+
+package com.esotericsoftware.kryo.util;
+
+import com.esotericsoftware.kryo.Kryo;
+
+/** Base class for implementations of {@link Generics} that stores generic type information.
+ * @author Nathan Sweet */
+abstract class BaseGenerics implements Generics {
+	final Kryo kryo;
+
+	private int genericTypesSize;
+	private GenericType[] genericTypes = new GenericType[16];
+	private int[] depths = new int[16];
+
+	protected BaseGenerics (Kryo kryo) {
+		this.kryo = kryo;
+	}
+
+	@Override
+	public void pushGenericType (GenericType fieldType) {
+		// Ensure genericTypes and depths capacity.
+		int size = genericTypesSize;
+		if (size + 1 == genericTypes.length) {
+			GenericType[] genericTypesNew = new GenericType[genericTypes.length << 1];
+			System.arraycopy(genericTypes, 0, genericTypesNew, 0, size);
+			genericTypes = genericTypesNew;
+			int[] depthsNew = new int[depths.length << 1];
+			System.arraycopy(depths, 0, depthsNew, 0, size);
+			depths = depthsNew;
+		}
+
+		genericTypesSize = size + 1;
+		genericTypes[size] = fieldType;
+		depths[size] = kryo.getDepth();
+	}
+
+	@Override
+	public void popGenericType () {
+		int size = genericTypesSize;
+		if (size == 0) return;
+		size--;
+		if (depths[size] < kryo.getDepth()) return;
+		genericTypes[size] = null;
+		genericTypesSize = size;
+	}
+
+	@Override
+	public GenericType[] nextGenericTypes () {
+		int index = genericTypesSize;
+		if (index > 0) {
+			index--;
+			GenericType genericType = genericTypes[index];
+			if (genericType.arguments == null) return null;
+			// The depth must match to prevent the types being wrong if a serializer doesn't call nextGenericTypes.
+			if (depths[index] == kryo.getDepth() - 1) {
+				pushGenericType(genericType.arguments[genericType.arguments.length - 1]);
+				return genericType.arguments;
+			}
+		}
+		return null;
+	}
+
+	@Override
+	public Class nextGenericClass () {
+		GenericType[] arguments = nextGenericTypes();
+		if (arguments == null) return null;
+		return arguments[0].resolve(this);
+	}
+
+	@Override
+	public int getGenericTypesSize () {
+		return genericTypesSize;
+	}
+
+}

src/com/esotericsoftware/kryo/util/DefaultGenerics.java

@@ -26,74 +26,18 @@
 
 /** Stores the generic type arguments and actual classes for type variables in the current location in the object graph.
  * @author Nathan Sweet */
-public final class DefaultGenerics implements Generics {
-	private final Kryo kryo;
-
-	private int genericTypesSize;
-	private GenericType[] genericTypes = new GenericType[16];
-	private int[] depths = new int[16];
+public final class DefaultGenerics extends BaseGenerics {
 
 	private int argumentsSize;
 	private Type[] arguments = new Type[16];
 
 	public DefaultGenerics (Kryo kryo) {
-		this.kryo = kryo;
-	}
-
-	@Override
-	public void pushGenericType (GenericType fieldType) {
-		// Ensure genericTypes and depths capacity.
-		int size = genericTypesSize;
-		if (size + 1 == genericTypes.length) {
-			GenericType[] genericTypesNew = new GenericType[genericTypes.length << 1];
-			System.arraycopy(genericTypes, 0, genericTypesNew, 0, size);
-			genericTypes = genericTypesNew;
-			int[] depthsNew = new int[depths.length << 1];
-			System.arraycopy(depths, 0, depthsNew, 0, size);
-			depths = depthsNew;
-		}
-
-		genericTypesSize = size + 1;
-		genericTypes[size] = fieldType;
-		depths[size] = kryo.getDepth();
-	}
-
-	@Override
-	public void popGenericType () {
-		int size = genericTypesSize;
-		if (size == 0) return;
-		size--;
-		if (depths[size] < kryo.getDepth()) return;
-		genericTypes[size] = null;
-		genericTypesSize = size;
-	}
-
-	@Override
-	public GenericType[] nextGenericTypes () {
-		int index = genericTypesSize;
-		if (index > 0) {
-			index--;
-			GenericType genericType = genericTypes[index];
-			if (genericType.arguments == null) return null;
-			// The depth must match to prevent the types being wrong if a serializer doesn't call nextGenericTypes.
-			if (depths[index] == kryo.getDepth() - 1) {
-				pushGenericType(genericType.arguments[genericType.arguments.length - 1]);
-				return genericType.arguments;
-			}
-		}
-		return null;
-	}
-
-	@Override
-	public Class nextGenericClass () {
-		GenericType[] arguments = nextGenericTypes();
-		if (arguments == null) return null;
-		return arguments[0].resolve(this);
+		super(kryo);
 	}
 
 	@Override
 	public int pushTypeVariables (GenericsHierarchy hierarchy, GenericType[] args) {
-		// Do not store type variables if hierarchy is empty or we do not have arguments for all root parameters.
+		// Do not store type variables if hierarchy is empty, or we do not have arguments for all root parameters.
 		if (hierarchy.total == 0 || hierarchy.rootTotal > args.length) return 0;
 
 		int startSize = this.argumentsSize;
@@ -145,11 +89,6 @@ public Class resolveTypeVariable (TypeVariable typeVariable) {
 		return null;
 	}
 
-	@Override
-	public int getGenericTypesSize () {
-		return genericTypesSize;
-	}
-
 	public String toString () {
 		StringBuilder buffer = new StringBuilder();
 		for (int i = 0; i < argumentsSize; i += 2) {

src/com/esotericsoftware/kryo/util/MinimalGenerics.java

@@ -0,0 +1,44 @@
+/* Copyright (c) 2008-2022, Nathan Sweet
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without modification, are permitted provided that the following
+ * conditions are met:
+ *
+ * - Redistributions of source code must retain the above copyright notice, this list of conditions and the following disclaimer.
+ * - Redistributions in binary form must reproduce the above copyright notice, this list of conditions and the following
+ * disclaimer in the documentation and/or other materials provided with the distribution.
+ * - Neither the name of Esoteric Software nor the names of its contributors may be used to endorse or promote products derived
+ * from this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING,
+ * BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT
+ * SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+ * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
+ * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. */
+
+package com.esotericsoftware.kryo.util;
+
+import com.esotericsoftware.kryo.Kryo;
+
+import java.lang.reflect.TypeVariable;
+
+/** Implementation of {@link Generics} that stores generic type information only. */
+public final class MinimalGenerics extends BaseGenerics {
+
+    public MinimalGenerics(Kryo kryo) {
+        super(kryo);
+    }
+
+    public int pushTypeVariables(GenericsHierarchy hierarchy, GenericType[] args) {
+        return 0;
+    }
+
+    public void popTypeVariables(int count) {
+
+    }
+
+    public Class resolveTypeVariable(TypeVariable typeVariable) {
+        return null;
+    }
+}

test/com/esotericsoftware/kryo/serializers/CollectionSerializerTest.java

@@ -32,6 +32,7 @@
 import java.util.Comparator;
 import java.util.LinkedList;
 import java.util.List;
+import java.util.Objects;
 import java.util.TreeSet;
 import java.util.concurrent.CopyOnWriteArrayList;
 
@@ -112,6 +113,17 @@ void testCopy () {
 		assertNotSame(objects1.get(0), objects2.get(0));
 	}
 
+	@Test
+	void testGenerics() {
+		kryo.register(HasGenerics.class);
+		kryo.register(ArrayList.class);
+
+		final HasGenerics test = new HasGenerics();
+		test.list.add("moo");
+
+		roundTrip(6, test);
+	}
+
 	public static class TreeSetSubclass<E> extends TreeSet<E> {
 		public TreeSetSubclass () {
 		}
@@ -120,4 +132,15 @@ public TreeSetSubclass (Comparator<? super E> comparator) {
 			super(comparator);
 		}
 	}
+
+	public static class HasGenerics {
+		public List<String> list = new ArrayList<>();
+
+		public boolean equals(Object o) {
+			if (this == o) return true;
+			if (o == null || getClass() != o.getClass()) return false;
+			HasGenerics that = (HasGenerics) o;
+			return Objects.equals(list, that.list);
+		}
+	}
 }

test/com/esotericsoftware/kryo/serializers/MapSerializerTest.java

@@ -117,7 +117,10 @@ void testGenerics () {
 		kryo.writeClassAndObject(output, test);
 		output.flush();
 
-		input = new Input(output.toBytes());
+		final byte[] bytes = output.toBytes();
+		assertEquals(bytes.length, 13);
+
+		input = new Input(bytes);
 		HasGenerics test2 = (HasGenerics)kryo.readClassAndObject(input);
 		assertArrayEquals(test.map.get("moo"), test2.map.get("moo"));
 	}