From 02185489561d6c9ba273da03491355721ff93b20 Mon Sep 17 00:00:00 2001
From: Sachin Patil <sachin.patil2@capitalone.com>
Date: Fri, 25 Aug 2023 14:15:11 -0500
Subject: [PATCH] #2436 - Updates to User guide & comments to indicate
 exception cases and fix for 7 test cases of Parameterized Type

---
 UserGuide.md                                          |  4 +++-
 gson/src/main/java/com/google/gson/GsonBuilder.java   | 11 ++++++++---
 .../test/java/com/google/gson/GsonBuilderTest.java    |  5 ++---
 3 files changed, 13 insertions(+), 7 deletions(-)

diff --git a/UserGuide.md b/UserGuide.md
index f519865434..3a42653bdb 100644
--- a/UserGuide.md
+++ b/UserGuide.md
@@ -405,7 +405,9 @@ gson.registerTypeAdapter(MyType.class, new MyDeserializer());
 gson.registerTypeAdapter(MyType.class, new MyInstanceCreator());
 ```
 
-`registerTypeAdapter` call checks if the type adapter implements more than one of these interfaces and register it for all of them.
+`registerTypeAdapter` call checks 
+1. if the type adapter implements more than one of these interfaces and register it for all of them.
+2. if the type adapter is for Object class or (JsonElements or any of its subclasses), it throws IllegalArgumentException.
 
 #### Writing a Serializer
 
diff --git a/gson/src/main/java/com/google/gson/GsonBuilder.java b/gson/src/main/java/com/google/gson/GsonBuilder.java
index f0c346f834..ccd37ba2b0 100644
--- a/gson/src/main/java/com/google/gson/GsonBuilder.java
+++ b/gson/src/main/java/com/google/gson/GsonBuilder.java
@@ -41,6 +41,8 @@
 import com.google.gson.reflect.TypeToken;
 import com.google.gson.stream.JsonReader;
 import com.google.gson.stream.JsonWriter;
+
+import java.lang.reflect.ParameterizedType;
 import java.lang.reflect.Type;
 import java.text.DateFormat;
 import java.util.ArrayDeque;
@@ -337,7 +339,7 @@ public GsonBuilder enableComplexMapKeySerialization() {
    *
    * <p>In general using inner classes with Gson should be avoided; they should be converted to {@code static}
    * nested classes if possible.
-   *
+   *Ø
    * @return a reference to this {@code GsonBuilder} object to fulfill the "Builder" pattern
    * @since 1.3
    */
@@ -664,6 +666,7 @@ public GsonBuilder setDateFormat(int dateStyle, int timeStyle) {
    * @param typeAdapter This object must implement at least one of the {@link TypeAdapter},
    * {@link InstanceCreator}, {@link JsonSerializer}, and a {@link JsonDeserializer} interfaces.
    * @return a reference to this {@code GsonBuilder} object to fulfill the "Builder" pattern
+   * @throws IllegalArgumentException if the Type adapter being registered is for Object class or (JsonElements or any of its subclasses)
    */
   @CanIgnoreReturnValue
   public GsonBuilder registerTypeAdapter(Type type, Object typeAdapter) {
@@ -689,8 +692,9 @@ public GsonBuilder registerTypeAdapter(Type type, Object typeAdapter) {
   }
 
   private boolean isTypeObjectOrJsonElements(Type type) {
-    return (type == Object.class
-            || JsonElement.class.isAssignableFrom((Class<?>) type));
+    return (!(type instanceof ParameterizedType) &&
+            (type == Object.class
+            || JsonElement.class.isAssignableFrom((Class<?>) type)));
   }
 
   /**
@@ -724,6 +728,7 @@ public GsonBuilder registerTypeAdapterFactory(TypeAdapterFactory factory) {
    * @param typeAdapter This object must implement at least one of {@link TypeAdapter},
    *        {@link JsonSerializer} or {@link JsonDeserializer} interfaces.
    * @return a reference to this {@code GsonBuilder} object to fulfill the "Builder" pattern
+   * @throws IllegalArgumentException if the Type adapter being registered is for a JsonElements or any of its subclasses
    * @since 1.7
    */
   @CanIgnoreReturnValue
diff --git a/gson/src/test/java/com/google/gson/GsonBuilderTest.java b/gson/src/test/java/com/google/gson/GsonBuilderTest.java
index 48b43aaf6c..2a50598b31 100644
--- a/gson/src/test/java/com/google/gson/GsonBuilderTest.java
+++ b/gson/src/test/java/com/google/gson/GsonBuilderTest.java
@@ -184,8 +184,7 @@ public void testRegisterTypeAdapterForCoreType() {
         String.class,
     };
     for (Type type : types) {
-      GsonBuilder gsonBuilder = new GsonBuilder();
-      assertThat(gsonBuilder.registerTypeAdapter(type, NULL_TYPE_ADAPTER)).isEqualTo(gsonBuilder);
+      new GsonBuilder().registerTypeAdapter(type, NULL_TYPE_ADAPTER);
     }
   }
 
@@ -282,6 +281,6 @@ public void testRegisterTypeHierarchyAdapterJsonElements() {
       assertThrows(IllegalArgumentException.class,
               () ->  gsonBuilder.registerTypeHierarchyAdapter((Class<?>) type, NULL_TYPE_ADAPTER));
     }
-    assertThat(gsonBuilder.registerTypeHierarchyAdapter(Object.class, NULL_TYPE_ADAPTER)).isEqualTo(gsonBuilder);
+    gsonBuilder.registerTypeHierarchyAdapter(Object.class, NULL_TYPE_ADAPTER);
   }
 }