From c20f18cc5d9adf4a0075fa941713707af95772ec Mon Sep 17 00:00:00 2001
From: Chris Povirk <cpovirk@google.com>
Date: Mon, 1 Nov 2021 12:23:45 -0400
Subject: [PATCH] Update code to prepare for nullness annotations in Guava.

Guava's current nullness annotations don't yet trigger Kotlin compile
errors. However, Guava did recently remove the misleading `@Nullable`
annotation from the parameter of `FutureCallback.onSuccess`:

Before:
https://github.com/google/guava/blob/v28.0/guava/src/com/google/common/util/concurrent/FutureCallback.java#L34

After:
https://github.com/google/guava/blob/v31.0.1/guava/src/com/google/common/util/concurrent/FutureCallback.java#L35

That means that a `FutureCallback<T>` can now implement `onSuccess(T)`
instead of `onSuccess(T?)`. And with a future change to Guava, it will
_have to_.

(For background, see the section on "Nullness annotations" in
https://github.com/google/guava/releases/tag/v31.0)

In order to make that change, this commit updates from from Guava 28.0
to Guava 31.0.1.

When I performed that update, I found that that pulled in a newer
version of the Checker Framework nullness annotations. That version was
build with a newer version of Gradle, so it generates Gradle module
metadata:
https://docs.gradle.org/current/userguide/publishing_gradle_module_metadata.html

That metadata declares that the Checker Framework annotations require
Java 1.8. Even the old version had in fact required Java 1.8 -- and so
had even the old version of Guava -- just without having that encoded in
its metadata. So I fixed this by setting targetCompatibility and
sourceCompatibility to 1.8 for kotlinx-coroutines-guava, too.
---
 integration/kotlinx-coroutines-guava/README.md         |  2 +-
 integration/kotlinx-coroutines-guava/build.gradle.kts  |  7 ++++++-
 .../kotlinx-coroutines-guava/src/ListenableFuture.kt   | 10 ++++------
 3 files changed, 11 insertions(+), 8 deletions(-)

diff --git a/integration/kotlinx-coroutines-guava/README.md b/integration/kotlinx-coroutines-guava/README.md
index 34b8e5818f..b930a6194c 100644
--- a/integration/kotlinx-coroutines-guava/README.md
+++ b/integration/kotlinx-coroutines-guava/README.md
@@ -62,6 +62,6 @@ Integration with Guava [ListenableFuture](https://github.com/google/guava/wiki/L
 
 <!--- INDEX com.google.common.util.concurrent -->
 
-[com.google.common.util.concurrent.ListenableFuture]: https://kotlin.github.io/kotlinx.coroutines/https://google.github.io/guava/releases/28.0-jre/api/docs/com/google/common/util/concurrent/ListenableFuture.html
+[com.google.common.util.concurrent.ListenableFuture]: https://kotlin.github.io/kotlinx.coroutines/https://google.github.io/guava/releases/31.0.1-jre/api/docs/com/google/common/util/concurrent/ListenableFuture.html
 
 <!--- END -->
diff --git a/integration/kotlinx-coroutines-guava/build.gradle.kts b/integration/kotlinx-coroutines-guava/build.gradle.kts
index 12a6ca70b7..ebddd3c9ce 100644
--- a/integration/kotlinx-coroutines-guava/build.gradle.kts
+++ b/integration/kotlinx-coroutines-guava/build.gradle.kts
@@ -2,12 +2,17 @@
  * Copyright 2016-2021 JetBrains s.r.o. Use of this source code is governed by the Apache 2.0 license.
  */
 
-val guavaVersion = "28.0-jre"
+val guavaVersion = "31.0.1-jre"
 
 dependencies {
     compile("com.google.guava:guava:$guavaVersion")
 }
 
+java {
+    targetCompatibility = JavaVersion.VERSION_1_8
+    sourceCompatibility = JavaVersion.VERSION_1_8
+}
+
 externalDocumentationLink(
     url = "https://google.github.io/guava/releases/$guavaVersion/api/docs/"
 )
diff --git a/integration/kotlinx-coroutines-guava/src/ListenableFuture.kt b/integration/kotlinx-coroutines-guava/src/ListenableFuture.kt
index d214cc6b1a..0820f1f101 100644
--- a/integration/kotlinx-coroutines-guava/src/ListenableFuture.kt
+++ b/integration/kotlinx-coroutines-guava/src/ListenableFuture.kt
@@ -135,10 +135,8 @@ public fun <T> ListenableFuture<T>.asDeferred(): Deferred<T> {
     // Finally, if this isn't done yet, attach a Listener that will complete the Deferred.
     val deferred = CompletableDeferred<T>()
     Futures.addCallback(this, object : FutureCallback<T> {
-        override fun onSuccess(result: T?) {
-            // Here we work with flexible types, so we unchecked cast to trick the type system
-            @Suppress("UNCHECKED_CAST")
-            runCatching { deferred.complete(result as T) }
+        override fun onSuccess(result: T) {
+            runCatching { deferred.complete(result) }
                 .onFailure { handleCoroutineException(EmptyCoroutineContext, it) }
         }
 
@@ -351,7 +349,7 @@ private class JobListenableFuture<T>(private val jobToCancel: Job): ListenableFu
      *
      * To preserve Coroutine's [CancellationException], this future points to either `T` or [Cancelled].
      */
-    private val auxFuture = SettableFuture.create<Any>()
+    private val auxFuture = SettableFuture.create<Any?>()
 
     /**
      * `true` if [auxFuture.get][ListenableFuture.get] throws [ExecutionException].
@@ -436,7 +434,7 @@ private class JobListenableFuture<T>(private val jobToCancel: Job): ListenableFu
     }
 
     /** See [get()]. */
-    private fun getInternal(result: Any): T = if (result is Cancelled) {
+    private fun getInternal(result: Any?): T = if (result is Cancelled) {
         throw CancellationException().initCause(result.exception)
     } else {
         // We know that `auxFuture` can contain either `T` or `Cancelled`.