Duplicate class ListenableFuture after update

[READ] Step 1: Are you in the right place?

Issues filed here should be about bugs in the code in this repository. If you have a general question, need help debugging, or fall into some other category use one of these other channels:

• For general technical questions, post a question on StackOverflow with the firebase tag.
• For general Firebase discussion, use the firebase-talk google group.
• For help troubleshooting your application that does not fall under one of the above categories, reach out to the personalized Firebase support channel.

[REQUIRED] Step 2: Describe your environment

• Android Studio version: 3.6.1
• Firebase Component: Firestore
• Component version: 21.4.1

[REQUIRED] Step 3: Describe the problem

Steps to reproduce:

After update Firebase BoM to 25.0.0 build failed:

Duplicate class com.google.common.util.concurrent.ListenableFuture found in modules jetified-guava-26.0-android.jar (com.google.guava:guava:26.0-android) and jetified-listenablefuture-1.0.jar (com.google.guava:listenablefuture:1.0)

[PromanSEW]

@drusak use this line instead:

implementation "com.google.guava:listenablefuture:9999.0-empty-to-avoid-conflict-with-guava"

[schmidt-sebastian]

The next release of Firestore will drop all direct dependencies on Guava, but our network stack continues to rely on Guava for some of its functionality. We are evaluating moving the network stack off of Guava too, but this will be very long process. Until that happens, issues like the one here will happen from time to time. Note that these conflicts are not Firebase specific, but can happen with any number of packages.