From 122d3ebaf3235edfb97c02abaadb4e52be223a42 Mon Sep 17 00:00:00 2001
From: themode <themode@outlook.fr>
Date: Thu, 3 Mar 2022 16:12:05 +0100
Subject: [PATCH] Test `hasPredictableViewers`

---
 .../minestom/server/entity/EntityView.java    |  5 +++-
 .../entity/EntityViewIntegrationTest.java     | 30 +++++++++++++++++--
 2 files changed, 32 insertions(+), 3 deletions(-)

diff --git a/src/main/java/net/minestom/server/entity/EntityView.java b/src/main/java/net/minestom/server/entity/EntityView.java
index e2acc67e8..b31a23b70 100644
--- a/src/main/java/net/minestom/server/entity/EntityView.java
+++ b/src/main/java/net/minestom/server/entity/EntityView.java
@@ -103,7 +103,7 @@ final class EntityView {
     public boolean hasPredictableViewers() {
         // Verify if this entity's viewers can be predicted from surrounding entities
         synchronized (mutex) {
-            return viewableOption.isAuto() && manualViewers.isEmpty();
+            return viewableOption.isAuto() && viewableOption.predictable && manualViewers.isEmpty();
         }
     }
 
@@ -140,6 +140,8 @@ final class EntityView {
         // The custom rule used to determine if an entity is viewable.
         private Predicate<T> predicate = entity -> true;
 
+        private boolean predictable = true;
+
         public Option(EntityTracker.Target<T> target, Predicate<T> loopPredicate,
                       Consumer<T> addition, Consumer<T> removal) {
             this.target = target;
@@ -192,6 +194,7 @@ final class EntityView {
         }
 
         void updateRule0(Predicate<T> predicate) {
+            this.predictable = false;
             update(loopPredicate, entity -> {
                 final boolean result = predicate.test(entity);
                 if (result != isRegistered(entity)) {
diff --git a/src/test/java/net/minestom/server/entity/EntityViewIntegrationTest.java b/src/test/java/net/minestom/server/entity/EntityViewIntegrationTest.java
index d549889e1..687d61375 100644
--- a/src/test/java/net/minestom/server/entity/EntityViewIntegrationTest.java
+++ b/src/test/java/net/minestom/server/entity/EntityViewIntegrationTest.java
@@ -6,8 +6,7 @@ import net.minestom.server.coordinate.Pos;
 import net.minestom.server.network.packet.server.play.SpawnLivingEntityPacket;
 import org.junit.jupiter.api.Test;
 
-import static org.junit.jupiter.api.Assertions.assertEquals;
-import static org.junit.jupiter.api.Assertions.assertTrue;
+import static org.junit.jupiter.api.Assertions.*;
 
 @EnvTest
 public class EntityViewIntegrationTest {
@@ -96,6 +95,33 @@ public class EntityViewIntegrationTest {
         assertEquals(1, p2.getViewers().size());
     }
 
+    @Test
+    public void predictableViewers(Env env) {
+        var instance = env.createFlatInstance();
+        var p = env.createPlayer(instance, new Pos(0, 42, 0));
+        assertTrue(p.hasPredictableViewers());
+        p.setAutoViewable(false);
+        assertFalse(p.hasPredictableViewers());
+        p.setAutoViewable(true);
+        assertTrue(p.hasPredictableViewers());
+        // MANUAL VIEWERS
+        {
+            var tmpPlayer = env.createPlayer(instance, new Pos(0, 42, 0));
+            p.addViewer(tmpPlayer);
+            assertFalse(p.hasPredictableViewers());
+            p.removeViewer(tmpPlayer);
+            tmpPlayer.remove();
+            assertTrue(p.hasPredictableViewers());
+        }
+        // CHANGE RULE
+        {
+            // May cause all subsequent `hasPredictableViewers` to return false
+            // due to the server not able detect always-true predicate
+            p.updateViewableRule(player -> false);
+            assertFalse(p.hasPredictableViewers());
+        }
+    }
+
     @Test
     public void livingVehicle(Env env) {
         var instance = env.createFlatInstance();