ARSC with multiple packages

[IgorEisberg]

So, I started researching on how resources.arsc with multiple packages are built.
Hopefully, we'll be able to add support for it in Apktool 3.x in the near future.

So far, I found 2 entirely different cases:

• Multiple packages of the same name: Typically found in framework-res.apk. Since duplicate package names aren't allowed when building normal apps, the only way to generate something like that is by defining staged aliases.
  https://cs.android.com/android/platform/superproject/main/+/main:frameworks/base/tools/aapt2/cmd/Link_test.cpp;l=473?q=staging-public-group-final
• Multiple packages of different names: Typically found in various apps. Those seem to be a result of merging a base app with static libraries (?) it depends on (basically like compiling a static binary vs. a binary with dynamic dependencies), although I'm not sure how to reproduce that...

Discussion is welcome. Will keep updating when I find something new.

[IgorEisberg]

Staged aliases support has now been implemented.

As for "Multiple packages of different names", this is the product of merger of multiple Dynamic Feature Modules produced by bundletool using the --mode=universal option (documented here) and is a one-way street. While separating the resource tables is theoretically possible, the same cannot be said for the merged classes in the dex files. There is no way to determine where each file/asset/class originated from, and no way of reproducing a similar merging without bundletool.