* Fix TypeAdapterRuntimeTypeWrapper not detecting reflective TreeTypeAdapter
Previously on serialization TypeAdapterRuntimeTypeWrapper preferred a
TreeTypeAdapter without `serializer` which falls back to the reflective
adapter. This behavior was incorrect because it caused the reflective
adapter for a Base class to be used for serialization (indirectly as
TreeTypeAdapter delegate) instead of using the reflective adapter for
a Subclass extending Base.
* Address review feedback
* Convert TypeAdapterRuntimeTypeWrapperTest to JUnit 4 test
* Prefer wrapped reflective adapter for serialization of subclass
* Detect reflective adapter used as delegate for Gson.FutureTypeAdapter
* Tiny style tweak.
Co-authored-by: Éamonn McManus <emcmanus@google.com>
The most notable impact of this change is that it adds several new public APIs:
- The TypeAdapter abstract class
- The TypeAdapter.Factory interface
- Four new methods on GsonBuilder to register streaming TypeAdapters (via Factory, via Class, via TypeToken, and as a type hierarchy)
- Three new methods on Gson to lookup streaming TypeAdapters (by type, by class, and to get the next type adapter)
Still outstanding:
- Write beautiful prose to document the new APIs above
- Change GsonBuilder's precedence so that both old and new-style type adapters are registered in one lot
Consolidated all of the different code paths that we use to construct instances. We now have an ObjectConstructor class that knows what type it constructs; this means that we don't need to ever do reflection to lookup a constructor at construction time.
Cleaned up some buggy type adapters, particularly around handling of null.
Removed dead code for object graph navigation.
Moved some classes into 'internal' so they are visible to the 'bind' subpackage.
Turned some TypeAdapterFactory/TypeAdapter pairs inside out so that the TypeAdapter is now the inner class. This is necessary so that the factories can take parameters.
Added an API to request the 'next' type adapter for a type. This allows type adapters to compose other type adapters. We're using this in two places:
- where the user has excluded a type from serialization but not deserialization, we need to use the "default" deserialization but interpose null on serialization. We create a type adapter that delegates for one and returns null for the other.
- similarly when a DOM type serializer is registered but no deserializer, or vice versa.
This is the biggest change to the MiniGson core.
For backwards compatibility, return null for the empty string.
Simplify JsonSerializationContext/JsonDeserializationContext to simply call through to GSON. SerializeDefault is currently unsupported.
More useful error messages when calling getAsBoolean on a JsonNull.
Remove currently unused MemoryRefStack. We might need this back again, though wiring it back in will be much more difficult because we don't interject ourselves between the users' various type adapters.
First preference: a type adapter registered for the runtime type
Second preference: a type adapter registered for the declared type
Third preference: reflective type adapter for the runtime type (if it is a sub class of the declared type)
Fourth preference: reflective type adapter for the declared type
If a type adapter is registered for a base class, then a field of that type is serialized with the type adapter instead of using the run-time type.
This fixes: CustomSerializerTest.testBaseClassSerializerInvokedForBaseClassFieldsHoldingSubClassInstances
