What are the unityeditorinternal and the unityengineinternal namespace and why are they missing from the docs ?

@IronPig_

Even though UnityEngineInternal and UnityEditorInternal are public namespaces with public types and public methods, since they are explicitly named "internal" and (probably) purposefully without a public documentation, it should mean that Unity Technologies does not want anyone to depend upon functionality present in these namespaces, as they may be types and methods that may change its public symbols and signatures easily and frequently, and can just cease to exist from one version of unity to another.

That said, there can be useful things inside there, which you should use at your own risk as they may change their type names, method signatures and internal behavior from one unity version to another.

One of such useful things is the UnityEditorInternal.ComponentUtility which contains the methods CopyComponent, PasteComponentAsNew and PasteComponentValues which let you easily copy one component from one gameobject to another.

I have made a 'quick and dirty' MenuItem to dump this info, it iterates over the types in these namespaces and spit out the public info. Use at will.

https://github.com/Gnumaru/UnityInternalsDumper

In the repo I put sample dumps which, again, can vary for each unity version.