Method fromJson throws JsonParseException instead of declared JsonSyntaxException

[DGorokhov123]

Gson version

I found a bug in GSON library. It's actual fo version 2.12.1

Description

Bug description:

Method fromJson signature looks like that:

public <T> T fromJson(String json, Class<T> classOfT) throws JsonSyntaxException {

so, it's obvious to coders to catch JsonSyntaxException:

try {
    goodGson.fromJson(badJson, User.class);
} catch (JsonSyntaxException e) {
    System.out.println("Good deserializer caught JsonSyntaxException");
}

Such construction works until we add Deserializer:

Gson badGson = new GsonBuilder()
          .registerTypeAdapter(User.class, new UserBadDeserializer())
          .create();

class UserBadDeserializer implements JsonDeserializer<User> {
    @Override
    public User deserialize(JsonElement json, Type typeOfT, 
                         JsonDeserializationContext context) throws JsonParseException {
        JsonObject jsonObject = json.getAsJsonObject();
        if (!jsonObject.has("name")) 
                     throw new JsonParseException("json should contain the name field!");
        String name = jsonObject.get("name").getAsString();
        return new User(name);
    }
}

The signature of deserialize method we should override, throws another
exception - JsonParseException, which is parent to JsonSyntaxException
and isn't caught by try-catch construction above
It flies further and may cause unexpected behaviour.

        try {
            try {
                badGson.fromJson(badJson, User.class);
            } catch (JsonSyntaxException e) {
                System.out.println("Good deserializer caught JsonSyntaxException");
            }
        } catch (RuntimeException e) {
            System.out.println("Bad deserializer didn't catch JsonSyntaxException, and " 
                        + e.getClass().getSimpleName() + " flew further");
        }

Solution 1 : Change signature of deserialize method to throw JsonSyntaxException.

Solution 2 : Change signature of fromJson method (and other methods calling
deserialize) to throw JsonParseException.

I've made a simple example to show this bug:
https://github.com/DGorokhov123/gson-bug

(С) Dmitriy Gorokhov [email protected], @DGorokhov123

[Shershah03]

Its seems changing it T _com.google.gson.JsonDeserializer.deserialize(JsonElement json, Type typeOfT, JsonDeserializationContext context) throws JsonSyntaxException is the best option.