Paper/patches/unapplied/server/0339-Don-t-run-entity-collision-code-if-not-needed.patch

From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
From: Spottedleaf <Spottedleaf@users.noreply.github.com>
Date: Wed, 15 Apr 2020 17:56:07 -0700
Subject: [PATCH] Don't run entity collision code if not needed

Will not run if:
Max entity cramming is disabled and the max collisions per entity is less than or equal to 0.
Entity#isPushable() returns false, meaning all entities will not be able to collide with this
entity anyways.
The entity's current team collision rule causes them to NEVER collide.

Co-authored-by: Owen1212055 <23108066+Owen1212055@users.noreply.github.com>

diff --git a/src/main/java/net/minecraft/world/entity/LivingEntity.java b/src/main/java/net/minecraft/world/entity/LivingEntity.java
index 4c32b26e29ca3db0a2f62052e14bcc3e4c1cdea5..cf18f17f181bc94a2b5f4ac6926c2388ec3178c8 100644
--- a/src/main/java/net/minecraft/world/entity/LivingEntity.java
+++ b/src/main/java/net/minecraft/world/entity/LivingEntity.java
@@ -3544,10 +3544,24 @@ public abstract class LivingEntity extends Entity implements Attackable {
         if (this.level().isClientSide()) {
             this.level().getEntities(EntityTypeTest.forClass(net.minecraft.world.entity.player.Player.class), this.getBoundingBox(), EntitySelector.pushableBy(this)).forEach(this::doPush);
         } else {
+            // Paper start - don't run getEntities if we're not going to use its result
+            if (!this.isPushable()) {
+                return;
+            }
+            net.minecraft.world.scores.Team team = this.getTeam();
+            if (team != null && team.getCollisionRule() == net.minecraft.world.scores.Team.CollisionRule.NEVER) {
+                return;
+            }
+
+            int i = this.level().getGameRules().getInt(GameRules.RULE_MAX_ENTITY_CRAMMING);
+            if (i <= 0 && this.level().paperConfig().collisions.maxEntityCollisions <= 0) {
+                return;
+            }
+            // Paper end - don't run getEntities if we're not going to use its result
             List<Entity> list = this.level().getEntities((Entity) this, this.getBoundingBox(), EntitySelector.pushableBy(this));
 
             if (!list.isEmpty()) {
-                int i = this.level().getGameRules().getInt(GameRules.RULE_MAX_ENTITY_CRAMMING);
+                // Paper - don't run getEntities if we're not going to use its result; moved up
 
                 if (i > 0 && list.size() > i - 1 && this.random.nextInt(4) == 0) {
                     int j = 0;