IssueTracker

Android developer documentation says in many places that
"Third party apps cannot actually respond to an intent with the ACTION_OPEN_DOCUMENT action"
"Only the system receives the ACTION_OPEN_DOCUMENT, so no need to test."
"On Android 4.4 (API level 19) and higher, you have the additional option of using the ACTION_OPEN_DOCUMENT intent, which displays a system-controlled picker UI"
"The user sees a system picker, allowing them to browse a documents provider and choose a location or document where the storage-related action takes place."

But in fact this is not true. Any app can register ACTION_OPEN_DOCUMENT intent filter and respond to these intents.

Maybe this is a bug in documentation but for me it looks like a violation of the core idea of Storage Access Framework.

I've seen this happening in real life with some file managers from Google Play.

Tested on emulator with API 21-29 and on several physical devices.

Screenshot and sample project attached.

Steps to reproduce:

1. Launch app, press the button on screen
2. Chooser is shown, including sample app itself