Where is the source code of Android Architecture Components?

As confirmed by Adam Powell, the source code of Architectural Components can be obtained only with the artifacts themselves:

Edit: Android Code Search

There is a very handy official online code search platform for Android: https://cs.android.com/

Try it, you'll love it!

Original Answer

As stated in Android team's official blog AndroidX Development is Now Even Better, the source code of AndroidX (previously support) lies in https://android.googlesource.com/platform/frameworks/support/+/androidx-master-dev. You can see AOSP AndroidX Contribution Guide on the page. There are details about:

• How to download the source code using repo
• How to build the project
• How to contribute to the project

All you need to do is following the instructions step by step, it won't take long to setup.

The other two useful links are:

• r.android.com Gerrit review tool
• public AndroidX tracker

It is also worth to be mentioned that in Android Fireside Chat (Android Dev Summit '18), the Android team are considering moving the source code of AndroidX to GitHub. We'll see whether it would happen in the future.

Here is the source for Lifecycle, Room, Paging and ViewModel.