Package saves lua ref of lua build func instead of stack index

src/Package.zig

@@ -97,7 +97,10 @@ pub const State = struct {
         };
     }
 
-    pub fn deinit(self: *State, gpa: Allocator) void {
+    pub fn deinit(self: *State, gpa: Allocator, lua: *const zlua.State) void {
+        for (self.packages.items(.build_func_ref)) |build_ref| {
+            lua.unref(zlua.REGISTRYINDEX, build_ref);
+        }
         self.package_table.deinit(gpa);
         self.string_state.deinit(gpa);
         self.packages.deinit(gpa);
@@ -119,8 +122,8 @@ id: Id = .none,
 /// name of Package
 name: String,
 version: std.SemanticVersion,
-/// Lua stack index of pkg from manifest
-lua_idx: i32,
+/// Lua registry reference to the package's build function
+build_func_ref: zlua.Idx,
 desc: String,
 homepage: String,
 license: String,
@@ -222,8 +225,14 @@ pub fn init(
     });
     lua.pop(1);
 
-    if (lua.getField(pkg, "build") != .function) return error.WrongLuaType;
-    lua.pop(1);
+    const build_func_ref = switch (lua.getField(pkg, "build")) {
+        .function => lua.ref(zlua.REGISTRYINDEX), // pops build
+        else => |kind| {
+            log.err("Package expected build to be a function, got {t}", .{kind});
+            return error.WrongLuaType;
+        },
+    };
+    errdefer lua.unref(zlua.REGISTRYINDEX, build_func_ref);
 
     var runtime_deps: Deps = .{ .start = 0, .count = 0 };
     var compile_deps: Deps = .{ .start = 0, .count = 0 };
@@ -295,7 +304,7 @@ pub fn init(
         .desc = desc,
         .homepage = homepage,
         .license = license,
-        .lua_idx = pkg,
+        .build_func_ref = build_func_ref,
         .compile_deps = compile_deps,
         .runtime_deps = runtime_deps,
     };

src/actions/build_package.zig

@@ -42,6 +42,8 @@ pub fn build(io: Io, gpa: Allocator, arena: Allocator, env: *std.process.Environ
     try lua_helpers.setupState(&lua);
 
     var state: Package.State = .empty;
+    defer state.deinit(arena, &lua);
+
     const pkg_id = try Package.collect(io, arena, &state, packa_dir, args.package_name, &lua, true);
     // TODO: fetch and install deps
 
@@ -99,13 +101,8 @@ pub fn build(io: Io, gpa: Allocator, arena: Allocator, env: *std.process.Environ
     };
     defer tar_root_dir.close(io);
 
-    switch (lua.getField(pkg.lua_idx, "build")) {
-        .function => {},
-        else => |kind| {
-            log.err("Expected build to be a function, got {t}", .{kind});
-            return error.WrongLuaType;
-        },
-    }
+    // Push package build func to stack for calling
+    assert(lua.rawGetI(zlua.REGISTRYINDEX, pkg.build_func_ref) == .function);
 
     // create b = Build{}
     lua.createTable(0, 8);

src/actions/info.zig

@@ -53,7 +53,7 @@ pub fn info(io: Io, gpa: Allocator, package_name: []const u8) !void {
     try lua_helpers.setupState(&lua);
 
     var state: Package.State = .empty;
-    defer state.deinit(gpa);
+    defer state.deinit(gpa, &lua);
 
     const pkg_id = try Package.collect(io, gpa, &state, packa_dir, package_name, &lua, false);
 

src/actions/install.zig

@@ -71,7 +71,7 @@ pub fn install(
     try lua_helpers.setupState(&lua);
 
     var state: Package.State = .empty;
-    defer state.deinit(gpa);
+    defer state.deinit(gpa, &lua);
 
     var package_ids: std.ArrayList(Package.Id) = try .initCapacity(gpa, args.package_names.len);
     defer package_ids.deinit(gpa);