Allow returning errors from ewext functions to lua.

ewext/Cargo.lock

@@ -40,14 +40,25 @@ checksum = "baf1de4339761588bc0619e3cbc0120ee582ebb74b53b4efbf79117bd2da40fd"
 
 [[package]]
 name = "ewext"
-version = "0.3.0"
+version = "0.4.0"
 dependencies = [
  "backtrace",
+ "eyre",
  "iced-x86",
  "libloading",
  "noita_api_macro",
 ]
 
+[[package]]
+name = "eyre"
+version = "0.6.12"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "7cd915d99f24784cdc19fd37ef22b97e3ff0ae756c7e492e9fbfe897d61e2aec"
+dependencies = [
+ "indenter",
+ "once_cell",
+]
+
 [[package]]
 name = "gimli"
 version = "0.31.1"
@@ -69,6 +80,12 @@ dependencies = [
  "lazy_static",
 ]
 
+[[package]]
+name = "indenter"
+version = "0.3.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "ce23b50ad8242c51a442f3ff322d56b02f08852c77e4c0b4d3fd684abc89c683"
+
 [[package]]
 name = "itoa"
 version = "1.0.11"
@@ -132,6 +149,12 @@ dependencies = [
  "memchr",
 ]
 
+[[package]]
+name = "once_cell"
+version = "1.20.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "1261fe7e33c73b354eab43b1273a57c8f967d0391e80353e51f764ac02cf6775"
+
 [[package]]
 name = "proc-macro2"
 version = "1.0.89"

ewext/Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "ewext"
-version = "0.3.0"
+version = "0.4.0"
 edition = "2021"
 
 [lib]
@@ -16,3 +16,4 @@ libloading = "0.8.5"
 backtrace = "0.3.74"
 iced-x86 = "1.21.0"
 noita_api_macro = {path = "noita_api_macro"}
+eyre = "0.6.12"

ewext/noita_api_macro/src/lib.rs

@@ -107,7 +107,9 @@ pub fn add_lua_fn(item: TokenStream) -> TokenStream {
     let fn_name_c = proc_macro2::Literal::c_string(CString::new(fn_name).unwrap().as_c_str());
     quote! {
         unsafe extern "C" fn #bridge_fn_name(lua: *mut lua_State) -> c_int {
-            #fn_name_ident(LuaState::new(lua)) as c_int
+            let lua_state = LuaState::new(lua);
+            lua_state.make_current();
+            crate::lua_state::LuaFnRet::do_return(#fn_name_ident(lua_state), lua_state)
         }
 
         LUA.lua_pushcclosure(lua, Some(#bridge_fn_name), 0);

ewext/src/lib.rs

@@ -6,8 +6,9 @@ use std::{
 };
 
 use addr_grabber::{grab_addrs, grabbed_fns, grabbed_globals};
+use eyre::bail;
 use lua_bindings::{lua_State, Lua51};
-use lua_state::LuaState;
+use lua_state::{LuaState, ValuesOnStack};
 use noita::{ntypes::Entity, NoitaPixelRun, ParticleWorldState};
 use noita_api_macro::add_lua_fn;
 
@@ -35,7 +36,7 @@ struct ExtState {
     particle_world_state: Option<ParticleWorldState>,
 }
 
-fn init_particle_world_state(lua: LuaState) -> c_int {
+fn init_particle_world_state(lua: LuaState) {
     println!("\nInitializing particle world state");
     let world_pointer = lua.to_integer(1);
     let chunk_map_pointer = lua.to_integer(2);
@@ -50,10 +51,9 @@ fn init_particle_world_state(lua: LuaState) -> c_int {
             runner: Default::default(),
         });
     });
-    0
 }
 
-fn encode_area(lua: LuaState) -> c_int {
+fn encode_area(lua: LuaState) -> ValuesOnStack {
     let lua = lua.raw();
     let start_x = unsafe { LUA.lua_tointeger(lua, 1) } as i32;
     let start_y = unsafe { LUA.lua_tointeger(lua, 2) } as i32;
@@ -67,10 +67,10 @@ fn encode_area(lua: LuaState) -> c_int {
         let runs = unsafe { pws.encode_area(start_x, start_y, end_x, end_y, encoded_buffer) };
         unsafe { LUA.lua_pushinteger(lua, runs as isize) };
     });
-    1
+    lua_state::ValuesOnStack(1)
 }
 
-fn make_ephemerial(lua: LuaState) -> c_int {
+fn make_ephemerial(lua: LuaState) -> eyre::Result<()> {
     unsafe {
         let entity_id = lua.to_integer(1) as u32;
 
@@ -87,16 +87,16 @@ fn make_ephemerial(lua: LuaState) -> c_int {
             out("ecx") _,
             out("eax") entity,
         );
-        if !entity.is_null() {
+        if entity.is_null() {
-            entity.cast::<c_void>().offset(0x8).cast::<u32>().write(0);
+            bail!("Entity {} not found", entity_id);
         }
+        entity.cast::<c_void>().offset(0x8).cast::<u32>().write(0);
     }
-    0
+    Ok(())
 }
 
-fn on_world_initialized(lua: LuaState) -> i32 {
+fn on_world_initialized(lua: LuaState) {
     grab_addrs(lua);
-    0
 }
 
 /// # Safety

ewext/src/lua_state.rs

@@ -1,10 +1,20 @@
-use std::ffi::CStr;
+use std::{
+    cell::Cell,
+    ffi::{c_char, c_int, CStr},
+    mem,
+};
+
+use eyre::OptionExt;
 
 use crate::{
     lua_bindings::{lua_CFunction, lua_State, LUA_GLOBALSINDEX},
     LUA,
 };
 
+thread_local! {
+    static CURRENT_LUA_STATE: Cell<Option<LuaState>> = Cell::default();
+}
+
 #[derive(Clone, Copy)]
 pub(crate) struct LuaState {
     lua: *mut lua_State,
@@ -15,6 +25,17 @@ impl LuaState {
         Self { lua }
     }
 
+    /// Returns a lua state that is considered "current". Usually set when we get called from noita.
+    pub(crate) fn current() -> eyre::Result<Self> {
+        CURRENT_LUA_STATE
+            .get()
+            .ok_or_eyre("No current lua state available")
+    }
+
+    pub(crate) fn make_current(self) {
+        CURRENT_LUA_STATE.set(Some(self));
+    }
+
     pub(crate) fn raw(&self) -> *mut lua_State {
         self.lua
     }
@@ -27,6 +48,12 @@ impl LuaState {
         unsafe { LUA.lua_tocfunction(self.lua, index) }
     }
 
+    pub(crate) fn push_string(&self, s: &str) {
+        unsafe {
+            LUA.lua_pushstring(self.lua, s.as_bytes().as_ptr() as *const c_char);
+        }
+    }
+
     pub(crate) fn get_global(&self, name: &CStr) {
         unsafe { LUA.lua_getfield(self.lua, LUA_GLOBALSINDEX, name.as_ptr()) };
     }
@@ -34,4 +61,45 @@ impl LuaState {
     pub(crate) fn pop_last(&self) {
         unsafe { LUA.lua_settop(self.lua, -2) };
     }
+
+    /// Raise an error with message `s`
+    ///
+    /// This takes String so that it gets deallocated properly, as this functions doesn't return.
+    unsafe fn raise_error(&self, s: String) -> ! {
+        self.push_string(&s);
+        mem::drop(s);
+        unsafe { LUA.lua_error(self.lua) };
+        // lua_error does not return.
+        unreachable!()
+    }
+}
+
+pub(crate) trait LuaFnRet {
+    fn do_return(self, lua: LuaState) -> c_int;
+}
+
+/// Function intends to return several values that it has on stack.
+pub(crate) struct ValuesOnStack(pub(crate) c_int);
+
+impl LuaFnRet for ValuesOnStack {
+    fn do_return(self, _lua: LuaState) -> c_int {
+        self.0
+    }
+}
+
+impl LuaFnRet for () {
+    fn do_return(self, _lua: LuaState) -> c_int {
+        0
+    }
+}
+
+impl<R: LuaFnRet> LuaFnRet for eyre::Result<R> {
+    fn do_return(self, lua: LuaState) -> c_int {
+        match self {
+            Ok(ok) => ok.do_return(lua),
+            Err(err) => unsafe {
+                lua.raise_error(format!("Error in ewext call: {:?}", err));
+            },
+        }
+    }
 }