GsonBuilder backwards compatibility broken, throws "Cannot override built-in adapter" error

[jirijanak]

Gson version

2.11

Java / Android version

Semeru JDK 21.0.5

Used tools

• Maven; version:
• Gradle; version: 8.12
• ProGuard (attach the configuration file please); version:
• ...

Description

We are currently maintaining a legacy application in an ongoing support mode. In order to address security vulnerabilities, we needed to update several third-party dependencies, which required upgrading to Gson version 2.11. However, after the update, another dependency, com.cloudant:cloudant-client:2.20.1 (https://github.com/cloudant/java-cloudant), began to fail. This dependency worked correctly with Gson 2.10.1 but now fails with Gson 2.11. The error encountered is as follows:

java.lang.IllegalArgumentException: Cannot override built-in adapter for class com.google.gson.JsonObject
 	at com.google.gson.GsonBuilder.registerTypeAdapter(GsonBuilder.java:714) ~[gson-2.11.0.jar:?]
 	at com.cloudant.client.org.lightcouch.internal.GsonHelper.initGson(GsonHelper.java:38) ~[cloudant-client-2.20.1.jar:?]
 	at com.cloudant.client.org.lightcouch.CouchDbClient.<init>(CouchDbClient.java:95) ~[cloudant-client-2.20.1.jar:?]
 	at com.cloudant.client.org.lightcouch.CouchDbClient.<init>(CouchDbClient.java:145) ~[cloudant-client-2.20.1.jar:?]
 	at com.cloudant.client.api.CloudantClient.<init>(CloudantClient.java:141) ~[cloudant-client-2.20.1.jar:?]
 	at com.cloudant.client.api.ClientBuilder.build(ClientBuilder.java:396) ~[cloudant-client-2.20.1.jar:?]

The issue appears to be related to how GsonBuilder is used in the method defined in https://github.com/cloudant/java-cloudant/blob/master/cloudant-client/src/main/java/com/cloudant/client/org/lightcouch/internal/GsonHelper.java

    public static GsonBuilder initGson(GsonBuilder gsonBuilder) {
        gsonBuilder.registerTypeAdapter(JsonObject.class, new JsonDeserializer<JsonObject>() {
            public JsonObject deserialize(JsonElement json,
                                          Type typeOfT, JsonDeserializationContext context)
                    throws JsonParseException {
                return json.getAsJsonObject();
            }
        });
        gsonBuilder.registerTypeAdapter(JsonObject.class, new JsonSerializer<JsonObject>() {
            public JsonElement serialize(JsonObject src, Type typeOfSrc,
                                         JsonSerializationContext context) {
                return src.getAsJsonObject();
            }

        });

        return gsonBuilder;
    }

It seems that something has changed in GsonBuilder between versions 2.10.1 and 2.11 that is now causing a conflict and breaking backward compatibility. Could you clarify whether this is a bug, or is it the intended behavior in the new Gson version?

Expected behavior

Considering this was minor version update, I would expect that GsonBuilder would continue to work as it was.

Actual behavior

It seems that something has changed in GsonBuilder between versions 2.10.1 and 2.11 that is now causing a conflict and breaking backward compatibility.

Reproduction steps

https://github.com/cloudant/java-cloudant/blob/master/cloudant-client/src/main/java/com/cloudant/client/org/lightcouch/internal/GsonHelper.java should still be able to register TypeAdapter in GsonBuilder.

NOTE: I can't change com.cloudant:cloudant-client:2.20.1 code. I know that it's deprecated, sunset and no longer supported by any team - but to replace it with some other library is involved change. Therefore I am trying to rather ask if backward compatibility of GsonBuilder could be kept.

Exception stack trace

java.lang.IllegalArgumentException: Cannot override built-in adapter for class com.google.gson.JsonObject
 	at com.google.gson.GsonBuilder.registerTypeAdapter(GsonBuilder.java:714) ~[gson-2.11.0.jar:?]
 	at com.cloudant.client.org.lightcouch.internal.GsonHelper.initGson(GsonHelper.java:38) ~[cloudant-client-2.20.1.jar:?]
 	at com.cloudant.client.org.lightcouch.CouchDbClient.<init>(CouchDbClient.java:95) ~[cloudant-client-2.20.1.jar:?]
 	at com.cloudant.client.org.lightcouch.CouchDbClient.<init>(CouchDbClient.java:145) ~[cloudant-client-2.20.1.jar:?]
 	at com.cloudant.client.api.CloudantClient.<init>(CloudantClient.java:141) ~[cloudant-client-2.20.1.jar:?]
 	at com.cloudant.client.api.ClientBuilder.build(ClientBuilder.java:396) ~[cloudant-client-2.20.1.jar:?]