Ensure mob effect IDs are namespaced so tipped arrows tick damage on living mobs

crates/horizon-client-core/src/potions.rs

@@ -91,6 +91,7 @@ pub fn effect(id: &str) -> Option<&'static EffectDef> {
 /// Namespaced effect ids for mob effect storage.
 pub fn namespaced(id: &'static str) -> &'static str {
     static IDS: OnceLock<HashMap<&'static str, &'static str>> = OnceLock::new();
+    let key = id.strip_prefix("minecraft:").unwrap_or(id);
     IDS.get_or_init(|| {
         EFFECTS
             .iter()
@@ -102,7 +103,7 @@ pub fn namespaced(id: &'static str) -> &'static str {
             })
             .collect()
     })
-    .get(id)
+    .get(key)
     .copied()
     .unwrap_or(id)
 }

crates/horizon-client/src/game/dispenser.rs

@@ -2140,6 +2140,11 @@ pub(super) fn tipped_effect(stack: &ItemStack) -> Option<(&'static str, i32)> {
             def.effects
                 .iter()
                 .find(|(id, _, _)| !horizon_client::brewing::effect(id).is_some_and(|e| e.instant))
-                .map(|(id, duration, _)| (*id, (duration / 8).max(1)))
+                .map(|(id, duration, _)| {
+                    (
+                        horizon_client::brewing::namespaced(id),
+                        (duration / 8).max(1),
+                    )
+                })
         })
 }

crates/horizon-client/src/mobs.rs

@@ -2264,15 +2264,21 @@ impl Mob {
         ) * self.speed_bonus();
         for (e, _, amp) in &self.extra.effects {
             match *e {
-                "minecraft:speed" => v *= 1.0 + 0.2 * f64::from(amp + 1),
-                "minecraft:slowness" => v *= (1.0 - 0.15 * f64::from(amp + 1)).max(0.0),
+                "speed" | "minecraft:speed" => v *= 1.0 + 0.2 * f64::from(amp + 1),
+                "slowness" | "minecraft:slowness" => {
+                    v *= (1.0 - 0.15 * f64::from(amp + 1)).max(0.0)
+                }
                 _ => {}
             }
         }
         v
     }
     pub fn has_effect(&self, effect: &str) -> bool {
-        self.extra.effects.iter().any(|e| e.0 == effect)
+        let stripped = effect.strip_prefix("minecraft:").unwrap_or(effect);
+        self.extra
+            .effects
+            .iter()
+            .any(|e| e.0.strip_prefix("minecraft:").unwrap_or(e.0) == stripped)
     }
     /// `LivingEntity.isCurrentlyGlowing`: the Glowing effect or the `Glowing` tag (on a
     /// server's client, `glowing` holds shared flag 6 instead).
@@ -2280,6 +2286,7 @@ impl Mob {
         self.glowing || self.has_effect("minecraft:glowing")
     }
     pub fn add_effect(&mut self, effect: &'static str, ticks: i32, amplifier: i32) {
+        let effect = horizon_client_core::potions::namespaced(effect);
         if let Some(e) = self.extra.effects.iter_mut().find(|e| e.0 == effect) {
             // MobEffectInstance.update: a stronger effect replaces with its
             // own duration, an equal one only extends it; a weaker one is

crates/horizon-client/src/mobs/ai.rs

@@ -1942,15 +1942,15 @@ fn tick_effects(m: &mut Mob) {
         let infinite = *ticks == -1;
         let count = if infinite { m.age as i32 } else { *ticks };
         match *effect {
-            "minecraft:poison"
+            "poison" | "minecraft:poison"
                 if count % interval(25) == 0 && !m.kind.flags.undead && m.health > 1.0 =>
             {
                 m.damage(1.0, Damage::of(DamageKind::Magic));
             }
-            "minecraft:wither" if count % interval(40) == 0 => {
+            "wither" | "minecraft:wither" if count % interval(40) == 0 => {
                 m.damage(1.0, Damage::of(DamageKind::Magic));
             }
-            "minecraft:regeneration"
+            "regeneration" | "minecraft:regeneration"
                 if count % interval(50) == 0 && !m.kind.flags.undead && m.alive() =>
             {
                 m.health = (m.health + 1.0).min(m.attrs.max_health);
@@ -2175,3 +2175,45 @@ mod frog_tests {
         );
     }
 }
+
+#[cfg(test)]
+mod poison_effect_tests {
+    use super::*;
+    use crate::mobs::MobTypes;
+    use std::sync::Arc;
+
+    #[test]
+    fn poison_effect_damages_living_mobs_but_not_undead() {
+        let root = std::path::Path::new(env!("CARGO_MANIFEST_DIR"))
+            .join("../../.local/horizon-client")
+            .join(horizon_core::VANILLA_VERSION);
+        if !root.join("entity-types.json").exists() {
+            return;
+        }
+        let data = MobTypes::load(&root).unwrap();
+
+        // Pig is not undead: should take damage from poison.
+        let pig_kind = Arc::new(data.types.get("minecraft:pig").unwrap().clone());
+        let mut pig = Mob::new(1, pig_kind, Vec3::new(0.0, 4.0, 0.0), 0.0);
+        pig.add_effect("poison", 100, 0);
+        assert_eq!(pig.extra.effects[0].0, "minecraft:poison");
+        let initial_pig_health = pig.health;
+        tick_effects(&mut pig);
+        assert_eq!(
+            pig.health,
+            initial_pig_health - 1.0,
+            "living mob should take 1.0 damage from poison"
+        );
+
+        // Zombie is undead: immune to poison damage.
+        let zombie_kind = Arc::new(data.types.get("minecraft:zombie").unwrap().clone());
+        let mut zombie = Mob::new(2, zombie_kind, Vec3::new(0.0, 4.0, 0.0), 0.0);
+        zombie.add_effect("poison", 100, 0);
+        let initial_zombie_health = zombie.health;
+        tick_effects(&mut zombie);
+        assert_eq!(
+            zombie.health, initial_zombie_health,
+            "undead mobs are immune to poison"
+        );
+    }
+}