Default null to nil when injectObjects is not set

src/thread.ts

@@ -217,9 +217,14 @@ export default class Thread {
                 this.lua.lua_pushboolean(this.address, target ? 1 : 0)
                 break
             default:
-                if (!this.typeExtensions.find((wrapper) => wrapper.extension.pushValue(this, decoratedValue, userdata))) {
-                    throw new Error(`The type '${typeof target}' is not supported by Lua`)
+                if (this.typeExtensions.find((wrapper) => wrapper.extension.pushValue(this, decoratedValue, userdata))) {
+                    break
                 }
+                if (target === null) {
+                    this.lua.lua_pushnil(this.address)
+                    break
+                }
+                throw new Error(`The type '${typeof target}' is not supported by Lua`)
         }
 
         if (decoratedValue.options.metatable) {

src/type-extensions/promise.ts

@@ -131,7 +131,7 @@ class PromiseTypeExtension<T = unknown> extends TypeExtension<Promise<T>> {
     }
 
     public pushValue(thread: Thread, decoration: Decoration<Promise<T>>): boolean {
-        if (Promise.resolve(decoration.target) !== decoration.target && typeof decoration.target.then !== 'function') {
+        if (Promise.resolve(decoration.target) !== decoration.target && typeof decoration.target?.then !== 'function') {
             return false
         }
         return super.pushValue(thread, decoration)

test/engine.test.js

@@ -782,6 +782,18 @@ describe('Engine', () => {
         expect(res).to.deep.equal([null, null, 'null'])
     })
 
+    it('null injected as nil', async () => {
+        const engine = await getEngine({ injectObjects: false })
+        engine.global.loadString(`
+        local args = { ... }
+        assert(type(args[1]) == "nil", string.format("expected first argument to be nil, got %s", type(args[1])))
+        return nil, args[1], tostring(nil)
+      `)
+        engine.global.pushValue(null)
+        const res = await engine.global.run(1)
+        expect(res).to.deep.equal([null, null, 'nil'])
+    })
+
     it('Nested callback from JS to Lua', async () => {
         const engine = await getEngine()
         engine.global.set('call', (fn) => fn())