Adds support for item use scripts

src/dynamic_data/script_handling/item_script.rs

@@ -1,2 +1,46 @@
+use crate::dynamic_data::Pokemon;
+use crate::static_data::EffectParameter;
+use std::sync::Arc;
+
 /// The script functions that are relevant to item use.
-pub trait ItemScript {}
+pub trait ItemScript {
+    /// Initializes the script with the given parameters for a specific item
+    fn on_initialize(&self, _pars: Vec<Arc<EffectParameter>>) -> anyhow_ext::Result<()> {
+        Ok(())
+    }
+
+    /// Returns whether the item is usable in the current context.
+    fn is_item_usable(&self) -> anyhow_ext::Result<bool> {
+        Ok(false)
+    }
+
+    /// Returns whether the item requires a target to be used.
+    fn requires_target(&self) -> anyhow_ext::Result<bool> {
+        Ok(false)
+    }
+
+    /// Returns whether the item is usable on the given target.
+    fn is_target_valid(&self, _target: &Pokemon) -> anyhow_ext::Result<bool> {
+        Ok(false)
+    }
+
+    /// Returns whether the item can be held by the given target.
+    fn is_holdable(&self) -> anyhow_ext::Result<bool> {
+        Ok(false)
+    }
+
+    /// Returns whether the item can be held by the given target.
+    fn can_target_hold(&self, _target: &Pokemon) -> anyhow_ext::Result<bool> {
+        Ok(false)
+    }
+
+    /// Handles the use of the item.
+    fn on_use(&self) -> anyhow_ext::Result<()> {
+        Ok(())
+    }
+
+    /// Handles the use of the item on the given target.
+    fn on_use_with_target(&self, _target: &Pokemon) -> anyhow_ext::Result<()> {
+        Ok(())
+    }
+}

src/script_implementations/wasm/item_script.rs

@@ -0,0 +1,167 @@
+use crate::dynamic_data::{ItemScript, Pokemon};
+use crate::script_implementations::wasm::export_registry::WasmVoidResultExtension;
+use crate::script_implementations::wasm::extern_ref::ExternRef;
+use crate::script_implementations::wasm::script_resolver::WebAssemblyEnvironmentData;
+use crate::static_data::EffectParameter;
+use crate::StringKey;
+use std::sync::Arc;
+
+/// A web assembly implementation of the item script.
+pub struct WebAssemblyItemScript {
+    /// The unique identifier of the script.
+    name: StringKey,
+
+    /// Pointer inside WebAssembly memory where the data is for this script.
+    self_ptr: u32,
+
+    /// Cached value for the is_usable function.
+    is_usable: Option<bool>,
+
+    /// Cached value for the requires_target function.
+    requires_target: Option<bool>,
+
+    /// Cached value for the is_holdable function.
+    is_holdable: Option<bool>,
+
+    /// The global runtime environment data.
+    environment: Arc<WebAssemblyEnvironmentData>,
+}
+
+impl WebAssemblyItemScript {
+    /// Create a new instance of the script.
+    pub fn new(name: StringKey, self_ptr: u32, environment: Arc<WebAssemblyEnvironmentData>) -> Self {
+        Self {
+            name,
+            self_ptr,
+            is_usable: None,
+            requires_target: None,
+            is_holdable: None,
+            environment,
+        }
+    }
+
+    /// Get the name of the script.
+    pub fn name(&self) -> &StringKey {
+        &self.name
+    }
+}
+
+/// Util macro to reduce function call verbosity.
+macro_rules! call_func {
+    ($func:ident, $env:ident, $self:ident $(, $par_name:expr)*) => {
+        match $func.call(&mut $env.store_mut(), $self.self_ptr $(, $par_name)*) {
+            Ok(res) => res.into_result_env($env)?,
+            Err(e) => return Err(e.into()),
+        };
+    }
+}
+
+/// Util macro to reduce extern ref instantiation verbosity.
+macro_rules! ex_ref {
+    ($env:ident, $value:expr) => {
+        ExternRef::new($env.as_ref(), $value.into())
+    };
+}
+
+impl ItemScript for WebAssemblyItemScript {
+    fn on_initialize(&self, pars: Vec<Arc<EffectParameter>>) -> anyhow_ext::Result<()> {
+        let env = &self.environment;
+        if let Some(func) = env.script_function_cache().item_on_initialize(env) {
+            let pars = pars
+                .into_iter()
+                .map(|p| ExternRef::<EffectParameter>::new(env, (&p).into()).index() as u32)
+                .collect::<Vec<_>>();
+            let wasm_ptr = env.copy_value_vec_to_wasm(&pars)?;
+            let r: u64 = unsafe { std::mem::transmute((wasm_ptr, pars.len() as u32)) };
+            call_func!(func, env, self, r);
+        }
+        Ok(())
+    }
+
+    fn is_item_usable(&self) -> anyhow_ext::Result<bool> {
+        if let Some(is_usable) = self.is_usable {
+            return Ok(is_usable);
+        }
+        let env = &self.environment;
+        if let Some(func) = env.script_function_cache().item_is_usable(env) {
+            let res_ptr = env.allocate_temp::<bool>(false);
+            call_func!(func, env, self, res_ptr.wasm_ptr);
+            let res = *res_ptr.value();
+            let self_mut = unsafe { (self as *const Self as *mut Self).as_mut().unwrap_unchecked() };
+            self_mut.is_usable = Some(res);
+            return Ok(res);
+        }
+        Ok(true)
+    }
+
+    fn requires_target(&self) -> anyhow_ext::Result<bool> {
+        if let Some(requires_target) = self.requires_target {
+            return Ok(requires_target);
+        }
+        let env = &self.environment;
+        if let Some(func) = env.script_function_cache().item_requires_target(env) {
+            let res_ptr = env.allocate_temp::<bool>(false);
+            call_func!(func, env, self, res_ptr.wasm_ptr);
+            let res = *res_ptr.value();
+            let self_mut = unsafe { (self as *const Self as *mut Self).as_mut().unwrap_unchecked() };
+            self_mut.requires_target = Some(res);
+            return Ok(res);
+        }
+        Ok(false)
+    }
+
+    fn is_target_valid(&self, target: &Pokemon) -> anyhow::Result<bool> {
+        let env = &self.environment;
+        if let Some(func) = env.script_function_cache().item_is_target_valid(env) {
+            let target = ex_ref!(env, target);
+            let res_ptr = env.allocate_temp::<bool>(false);
+            call_func!(func, env, self, target, res_ptr.wasm_ptr);
+            return Ok(*res_ptr.value());
+        }
+        Ok(false)
+    }
+
+    fn is_holdable(&self) -> anyhow::Result<bool> {
+        if let Some(is_holdable) = self.is_holdable {
+            return Ok(is_holdable);
+        }
+        let env = &self.environment;
+        if let Some(func) = env.script_function_cache().item_is_holdable(env) {
+            let res_ptr = env.allocate_temp::<bool>(false);
+            call_func!(func, env, self, res_ptr.wasm_ptr);
+            let res = *res_ptr.value();
+            let self_mut = unsafe { (self as *const Self as *mut Self).as_mut().unwrap_unchecked() };
+            self_mut.is_holdable = Some(res);
+            return Ok(res);
+        }
+        Ok(false)
+    }
+
+    fn can_target_hold(&self, target: &Pokemon) -> anyhow::Result<bool> {
+        let env = &self.environment;
+        if let Some(func) = env.script_function_cache().item_can_target_hold(env) {
+            let target = ex_ref!(env, target);
+            let res_ptr = env.allocate_temp::<bool>(false);
+            call_func!(func, env, self, target, res_ptr.wasm_ptr);
+            return Ok(*res_ptr.value());
+        }
+        Ok(false)
+    }
+
+    fn on_use(&self) -> anyhow::Result<()> {
+        let env = &self.environment;
+        if let Some(func) = env.script_function_cache().item_on_use(env) {
+            call_func!(func, env, self);
+        }
+        Ok(())
+    }
+
+    fn on_use_with_target(&self, target: &Pokemon) -> anyhow::Result<()> {
+        let env = &self.environment;
+        if let Some(func) = env.script_function_cache().item_on_use_with_target(env) {
+            let target = ex_ref!(env, target);
+            call_func!(func, env, self, target);
+        }
+        Ok(())
+    }
+}

src/script_implementations/wasm/mod.rs

@@ -1,7 +1,9 @@
 /// The export registry module deals with registering all functions we require in WebAssembly.
 mod export_registry;
-/// A hacky extern ref implementation to ensure the client does not do things it is not allowed to do.
+/// A extern ref implementation to ensure the client does not do things it is not allowed to do.
 pub(crate) mod extern_ref;
+/// The item script module deals with the actual running of WASM functions.
+pub mod item_script;
 /// The script module deals with the actual running of WASM functions.
 pub mod script;
 /// A cache of all script functions for easy calls

src/script_implementations/wasm/script_function_cache.rs

@@ -18,7 +18,7 @@ use wasmer::{FromToNativeWasmType, TypedFunction};
 macro_rules! script_function_cache {
     (
         $(
-            $name:ident($($par_type:ty),*$(,)?)
+            $prefix:ident, $name:ident($($par_type:ty),*$(,)?)
         )*
     ) => {
         #[derive(Default)]
@@ -38,7 +38,7 @@ macro_rules! script_function_cache {
                     #[allow(unused_parens)]
                     fn [<initialize_ $name>](&self, env: &Arc<WebAssemblyEnvironmentData>) {
                         let exported = env.exported_functions();
-                        let f = exported.get::<StringKey>(&stringify!([< script_ $name >]).into());
+                        let f = exported.get::<StringKey>(&stringify!([< $prefix $name >]).into());
                         if let Some(f) = f {
                             let func: TypedFunction<(u32 $(,$par_type)*), WasmVoidResult> = f.typed(&env.store_ref()).unwrap();
                             let _ = self.$name.write().insert(func);
@@ -121,61 +121,71 @@ unsafe impl<T> FromToNativeWasmType for WasmPtr<T> {
 }
 
 script_function_cache! {
-    stack()
-    on_remove()
-    on_initialize(ExternRef<dyn DynamicLibrary>, u64)
-    on_before_turn(ExternRef<TurnChoice>)
-    change_speed(ExternRef<TurnChoice>, WasmPtr<u32>)
-    change_priority(ExternRef<TurnChoice>, WasmPtr<i8>)
-    change_move(ExternRef<TurnChoice>, WasmPtr<ExternRef<StringKey>>)
-    change_number_of_hits(ExternRef<TurnChoice>, WasmPtr<u8>)
-    prevent_move(ExternRef<ExecutingMove>, WasmPtr<bool>)
-    fail_move(ExternRef<ExecutingMove>, WasmPtr<bool>)
-    stop_before_move(ExternRef<ExecutingMove>, WasmPtr<bool>)
-    on_before_move(ExternRef<ExecutingMove>)
-    fail_incoming_move(ExternRef<ExecutingMove>, ExternRef<Pokemon>, WasmPtr<bool>)
-    is_invulnerable(ExternRef<ExecutingMove>, ExternRef<Pokemon>, WasmPtr<bool>)
-    on_move_miss(ExternRef<ExecutingMove>, ExternRef<Pokemon>)
-    change_move_type(ExternRef<ExecutingMove>, ExternRef<Pokemon>, u8, WasmPtr<TypeIdentifier>)
-    change_effectiveness(ExternRef<ExecutingMove>, ExternRef<Pokemon>, u8, WasmPtr<f32>)
-    block_critical(ExternRef<ExecutingMove>, ExternRef<Pokemon>, u8, WasmPtr<bool>)
-    block_incoming_critical(ExternRef<ExecutingMove>, ExternRef<Pokemon>, u8, WasmPtr<bool>)
-    change_accuracy(ExternRef<ExecutingMove>, ExternRef<Pokemon>, u8, WasmPtr<u8>)
-    change_critical_stage(ExternRef<ExecutingMove>, ExternRef<Pokemon>, u8, WasmPtr<u8>)
-    change_critical_modifier(ExternRef<ExecutingMove>, ExternRef<Pokemon>, u8, WasmPtr<f32>)
-    change_stab_modifier(ExternRef<ExecutingMove>, ExternRef<Pokemon>, u8, WasmPtr<f32>)
-    change_base_power(ExternRef<ExecutingMove>, ExternRef<Pokemon>, u8, WasmPtr<u8>)
-    bypass_defensive_stat_boost(ExternRef<ExecutingMove>, ExternRef<Pokemon>, u8, WasmPtr<bool>)
-    bypass_offensive_stat_boost(ExternRef<ExecutingMove>, ExternRef<Pokemon>, u8, WasmPtr<bool>)
-    change_offensive_stat_value(ExternRef<ExecutingMove>, ExternRef<Pokemon>, u8, WasmPtr<u32>)
-    change_defensive_stat_value(ExternRef<ExecutingMove>, ExternRef<Pokemon>, u8, WasmPtr<u32>)
-    change_damage_stat_modifier(ExternRef<ExecutingMove>, ExternRef<Pokemon>, u8, WasmPtr<f32>)
-    change_damage_modifier(ExternRef<ExecutingMove>, ExternRef<Pokemon>, u8, WasmPtr<f32>)
-    change_damage(ExternRef<ExecutingMove>, ExternRef<Pokemon>, u8, WasmPtr<u32>)
-    change_incoming_damage(ExternRef<ExecutingMove>, ExternRef<Pokemon>, u8, WasmPtr<u32>)
-    on_incoming_hit(ExternRef<ExecutingMove>, ExternRef<Pokemon>, u8)
-    on_opponent_faints(ExternRef<ExecutingMove>, ExternRef<Pokemon>, u8)
-    prevent_stat_boost_change(ExternRef<Pokemon>, u8, i8, u8, WasmPtr<bool>)
-    prevent_secondary_effect(ExternRef<ExecutingMove>, ExternRef<Pokemon>, u8, WasmPtr<bool>)
-    change_effect_chance(ExternRef<ExecutingMove>, ExternRef<Pokemon>, u8, WasmPtr<f32>)
-    change_incoming_effect_chance(ExternRef<ExecutingMove>, ExternRef<Pokemon>, u8, WasmPtr<f32>)
-    on_secondary_effect(ExternRef<ExecutingMove>, ExternRef<Pokemon>, u8)
-    on_after_hits(ExternRef<ExecutingMove>, ExternRef<Pokemon>)
-    prevent_self_switch(ExternRef<TurnChoice>, WasmPtr<bool>)
-    prevent_opponent_switch(ExternRef<TurnChoice>, WasmPtr<bool>)
-    on_fail(ExternRef<Pokemon>)
-    on_opponent_fail(ExternRef<Pokemon>)
-    prevent_self_run_away(ExternRef<TurnChoice>, WasmPtr<bool>)
-    prevent_opponent_run_away(ExternRef<TurnChoice>, WasmPtr<bool>)
-    on_end_turn()
-    on_damage(ExternRef<Pokemon>, u8, u32, u32)
-    on_faint(ExternRef<Pokemon>, u8)
-    on_switch_in(ExternRef<Pokemon>)
-    on_after_held_item_consume(ExternRef<Pokemon>, ExternRef<dyn Item>)
-    change_experience_gained(ExternRef<Pokemon>, ExternRef<Pokemon>, WasmPtr<u32>)
-    share_experience(ExternRef<Pokemon>, ExternRef<Pokemon>, WasmPtr<bool>)
-    block_weather(ExternRef<Battle>, WasmPtr<bool>)
-    change_capture_rate_bonus(ExternRef<Pokemon>, ExternRef<dyn Item>, WasmPtr<u8>)
+    script_, stack()
+    script_, on_remove()
+    script_, on_initialize(ExternRef<dyn DynamicLibrary>, u64)
+    script_, on_before_turn(ExternRef<TurnChoice>)
+    script_, change_speed(ExternRef<TurnChoice>, WasmPtr<u32>)
+    script_, change_priority(ExternRef<TurnChoice>, WasmPtr<i8>)
+    script_, change_move(ExternRef<TurnChoice>, WasmPtr<ExternRef<StringKey>>)
+    script_, change_number_of_hits(ExternRef<TurnChoice>, WasmPtr<u8>)
+    script_, prevent_move(ExternRef<ExecutingMove>, WasmPtr<bool>)
+    script_, fail_move(ExternRef<ExecutingMove>, WasmPtr<bool>)
+    script_, stop_before_move(ExternRef<ExecutingMove>, WasmPtr<bool>)
+    script_, on_before_move(ExternRef<ExecutingMove>)
+    script_, fail_incoming_move(ExternRef<ExecutingMove>, ExternRef<Pokemon>, WasmPtr<bool>)
+    script_, is_invulnerable(ExternRef<ExecutingMove>, ExternRef<Pokemon>, WasmPtr<bool>)
+    script_, on_move_miss(ExternRef<ExecutingMove>, ExternRef<Pokemon>)
+    script_, change_move_type(ExternRef<ExecutingMove>, ExternRef<Pokemon>, u8, WasmPtr<TypeIdentifier>)
+    script_, change_effectiveness(ExternRef<ExecutingMove>, ExternRef<Pokemon>, u8, WasmPtr<f32>)
+    script_, block_critical(ExternRef<ExecutingMove>, ExternRef<Pokemon>, u8, WasmPtr<bool>)
+    script_, block_incoming_critical(ExternRef<ExecutingMove>, ExternRef<Pokemon>, u8, WasmPtr<bool>)
+    script_, change_accuracy(ExternRef<ExecutingMove>, ExternRef<Pokemon>, u8, WasmPtr<u8>)
+    script_, change_critical_stage(ExternRef<ExecutingMove>, ExternRef<Pokemon>, u8, WasmPtr<u8>)
+    script_, change_critical_modifier(ExternRef<ExecutingMove>, ExternRef<Pokemon>, u8, WasmPtr<f32>)
+    script_, change_stab_modifier(ExternRef<ExecutingMove>, ExternRef<Pokemon>, u8, WasmPtr<f32>)
+    script_, change_base_power(ExternRef<ExecutingMove>, ExternRef<Pokemon>, u8, WasmPtr<u8>)
+    script_, bypass_defensive_stat_boost(ExternRef<ExecutingMove>, ExternRef<Pokemon>, u8, WasmPtr<bool>)
+    script_, bypass_offensive_stat_boost(ExternRef<ExecutingMove>, ExternRef<Pokemon>, u8, WasmPtr<bool>)
+    script_, change_offensive_stat_value(ExternRef<ExecutingMove>, ExternRef<Pokemon>, u8, WasmPtr<u32>)
+    script_, change_defensive_stat_value(ExternRef<ExecutingMove>, ExternRef<Pokemon>, u8, WasmPtr<u32>)
+    script_, change_damage_stat_modifier(ExternRef<ExecutingMove>, ExternRef<Pokemon>, u8, WasmPtr<f32>)
+    script_, change_damage_modifier(ExternRef<ExecutingMove>, ExternRef<Pokemon>, u8, WasmPtr<f32>)
+    script_, change_damage(ExternRef<ExecutingMove>, ExternRef<Pokemon>, u8, WasmPtr<u32>)
+    script_, change_incoming_damage(ExternRef<ExecutingMove>, ExternRef<Pokemon>, u8, WasmPtr<u32>)
+    script_, on_incoming_hit(ExternRef<ExecutingMove>, ExternRef<Pokemon>, u8)
+    script_, on_opponent_faints(ExternRef<ExecutingMove>, ExternRef<Pokemon>, u8)
+    script_, prevent_stat_boost_change(ExternRef<Pokemon>, u8, i8, u8, WasmPtr<bool>)
+    script_, prevent_secondary_effect(ExternRef<ExecutingMove>, ExternRef<Pokemon>, u8, WasmPtr<bool>)
+    script_, change_effect_chance(ExternRef<ExecutingMove>, ExternRef<Pokemon>, u8, WasmPtr<f32>)
+    script_, change_incoming_effect_chance(ExternRef<ExecutingMove>, ExternRef<Pokemon>, u8, WasmPtr<f32>)
+    script_, on_secondary_effect(ExternRef<ExecutingMove>, ExternRef<Pokemon>, u8)
+    script_, on_after_hits(ExternRef<ExecutingMove>, ExternRef<Pokemon>)
+    script_, prevent_self_switch(ExternRef<TurnChoice>, WasmPtr<bool>)
+    script_, prevent_opponent_switch(ExternRef<TurnChoice>, WasmPtr<bool>)
+    script_, on_fail(ExternRef<Pokemon>)
+    script_, on_opponent_fail(ExternRef<Pokemon>)
+    script_, prevent_self_run_away(ExternRef<TurnChoice>, WasmPtr<bool>)
+    script_, prevent_opponent_run_away(ExternRef<TurnChoice>, WasmPtr<bool>)
+    script_, on_end_turn()
+    script_, on_damage(ExternRef<Pokemon>, u8, u32, u32)
+    script_, on_faint(ExternRef<Pokemon>, u8)
+    script_, on_switch_in(ExternRef<Pokemon>)
+    script_, on_after_held_item_consume(ExternRef<Pokemon>, ExternRef<dyn Item>)
+    script_, change_experience_gained(ExternRef<Pokemon>, ExternRef<Pokemon>, WasmPtr<u32>)
+    script_, share_experience(ExternRef<Pokemon>, ExternRef<Pokemon>, WasmPtr<bool>)
+    script_, block_weather(ExternRef<Battle>, WasmPtr<bool>)
+    script_, change_capture_rate_bonus(ExternRef<Pokemon>, ExternRef<dyn Item>, WasmPtr<u8>)
+
+    // Item script functions
+    item_script_, item_on_initialize(u64)
+    item_script_, item_is_usable(WasmPtr<bool>)
+    item_script_, item_requires_target(WasmPtr<bool>)
+    item_script_, item_is_target_valid(ExternRef<Pokemon>, WasmPtr<bool>)
+    item_script_, item_is_holdable(WasmPtr<bool>)
+    item_script_, item_can_target_hold(ExternRef<Pokemon>, WasmPtr<bool>)
+    item_script_, item_on_use()
+    item_script_, item_on_use_with_target(ExternRef<Pokemon>)
 }
 
 impl ScriptFunctionCache {

src/script_implementations/wasm/script_resolver.rs

@@ -15,6 +15,7 @@ use wasmer::{
 use crate::dynamic_data::{ItemScript, Script, ScriptOwnerData, ScriptResolver};
 use crate::script_implementations::wasm::export_registry::{register_webassembly_funcs, WasmObject};
 use crate::script_implementations::wasm::extern_ref::ExternRef;
+use crate::script_implementations::wasm::item_script::WebAssemblyItemScript;
 use crate::script_implementations::wasm::script::WebAssemblyScript;
 use crate::script_implementations::wasm::script_function_cache::ScriptFunctionCache;
 use crate::script_implementations::wasm::temp_wasm_allocator::{AllocatedObject, TempWasmAllocator};
@@ -35,8 +36,14 @@ pub struct WebAssemblyScriptResolver {
     /// This is the WASM function to load a script.
     load_script_fn: Option<TypedFunction<(u8, ExternRef<StringKey>), u32>>,
 
+    /// This is the WASM function to load an item script.
+    load_item_script_fn: Option<TypedFunction<ExternRef<StringKey>, u32>>,
+
     /// The data for use in the scripting function calls.
     environment_data: Arc<WebAssemblyEnvironmentData>,
+
+    /// A cache of all item scripts for faster calls.
+    item_scripts: RwLock<HashMap<StringKey, Arc<dyn ItemScript>>>,
 }
 
 /// This struct allows us to index a hashmap with both a category and name of a script.
@@ -68,7 +75,9 @@ impl WebAssemblyScriptResolver {
             modules: Default::default(),
             instances: Default::default(),
             load_script_fn: None,
+            load_item_script_fn: None,
             environment_data: environment,
+            item_scripts: Default::default(),
         };
 
         Arc::new(s)
@@ -148,6 +157,11 @@ impl WebAssemblyScriptResolver {
                     let self_mut = (self as *const Self as *mut Self).as_mut().unwrap();
                     self_mut.load_script_fn = Some(f.typed(&self.store_ref())?)
                 }
+                #[allow(clippy::unwrap_used)] // We know this is valid.
+                if let Some(f) = exported_functions.get::<StringKey>(&"load_item_script".into()) {
+                    let self_mut = (self as *const Self as *mut Self).as_mut().unwrap();
+                    self_mut.load_item_script_fn = Some(f.typed(&self.store_ref())?)
+                }
             }
             if let Some(f) = exported_functions.get::<StringKey>(&"allocate_mem".into()) {
                 let _ = self
@@ -194,7 +208,30 @@ impl ScriptResolver for WebAssemblyScriptResolver {
     }
 
     fn load_item_script(&self, _key: &dyn Item) -> Result<Option<Arc<dyn ItemScript>>> {
-        todo!()
+        if self.load_item_script_fn.is_none() {
+            return Ok(None);
+        }
+
+        if let Some(script) = self.item_scripts.read().get(_key.name()) {
+            return Ok(Some(script.clone()));
+        }
+        let mut item_scripts_write_lock = self.item_scripts.write();
+        let script_ptr = self
+            .load_item_script_fn
+            .as_ref()
+            // should never happen, as we check for this above.
+            .ok_or(anyhow!("Load item script function was not found"))?
+            .call(
+                &mut self.store_mut(),
+                ExternRef::new_with_resolver(self, WasmObject::StringKey(_key.name().clone())),
+            )?;
+        let script = Arc::new(WebAssemblyItemScript::new(
+            _key.name().clone(),
+            script_ptr,
+            self.environment_data.clone(),
+        ));
+        item_scripts_write_lock.insert(_key.name().clone(), script.clone());
+        Ok(Some(script))
     }
 
     fn as_any(&self) -> &dyn Any {