RuntimeTypeAdapterFactory depends on internal API (JPMS, Java 9+)

[miasma]

The RuntimeTypeAdapterFactory code example (https://github.com/google/gson/blob/master/extras/src/main/java/com/google/gson/typeadapters/RuntimeTypeAdapterFactory.java) depends on the internal API class com.google.gson.internal.Streams, which is not exported when depending on gson in a JPMS project using module path.

Unless there's some easy fix available, currently one has to make a copy of Streams, LazilyParsedNumber, and TypeAdapters classes from the internal packages in order to use this provided class.

[Marcono1234]

one has to make a copy of Streams, LazilyParsedNumber, and TypeAdapters classes

The classes LazilyParsedNumber and TypeAdapters would only be needed if you wanted to copy the exact code of TypeAdapters.JSON_ELEMENT, right? They don't appear to be needed directly by RuntimeTypeAdapterFactory.

I have tried implementing a fix in #1959, please let me know if that works for you.

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Note that I am not a maintainer of this project.