Add a consumer parameter to ProjectileSource#launchProjectile (#8374)

Co-authored-by: MelnCat <melncatuwu@gmail.com>

patches/api/0394-Add-a-consumer-parameter-to-ProjectileSource-launchP.patch

@@ -0,0 +1,35 @@
+From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
+From: MelnCat <melncatuwu@gmail.com>
+Date: Mon, 19 Sep 2022 14:04:13 -0700
+Subject: [PATCH] Add a consumer parameter to ProjectileSource#launchProjectile
+
+
+diff --git a/src/main/java/org/bukkit/projectiles/ProjectileSource.java b/src/main/java/org/bukkit/projectiles/ProjectileSource.java
+index eabd8b926ec1c934cd7e77b7cc6adfae16771021..6cb28e65b82198b19f159f8e8334208f7f62d394 100644
+--- a/src/main/java/org/bukkit/projectiles/ProjectileSource.java
++++ b/src/main/java/org/bukkit/projectiles/ProjectileSource.java
+@@ -31,4 +31,24 @@ public interface ProjectileSource {
+      */
+     @NotNull
+     public <T extends Projectile> T launchProjectile(@NotNull Class<? extends T> projectile, @Nullable Vector velocity);
++    
++    // Paper start
++    /**
++     * Launches a {@link Projectile} from the ProjectileSource with an
++     * initial velocity, with the supplied function run before the
++     * entity is added to the world.
++     * <br>
++     * Note that when the function is run, the entity will not be actually in
++     * the world. Any operation involving such as teleporting the entity is undefined
++     * until after this function returns.
++     *
++     * @param <T> a projectile subclass
++     * @param projectile class of the projectile to launch
++     * @param velocity the velocity with which to launch
++     * @param function the function to be run before the entity is spawned
++     * @return the launched projectile
++     */
++    @NotNull
++    public <T extends Projectile> T launchProjectile(@NotNull Class<? extends T> projectile, @Nullable Vector velocity, @Nullable org.bukkit.util.Consumer<T> function);
++    // Paper end
+ }