Implement push_into_stack/from_stack for Option<T>

src/conversion.rs

@@ -1063,6 +1063,15 @@ impl<'lua, T: IntoLua<'lua>> IntoLua<'lua> for Option<T> {
             None => Ok(Nil),
         }
     }
+
+    #[inline]
+    unsafe fn push_into_stack(self, lua: &'lua Lua) -> Result<()> {
+        match self {
+            Some(val) => val.push_into_stack(lua)?,
+            None => ffi::lua_pushnil(lua.state()),
+        }
+        Ok(())
+    }
 }
 
 impl<'lua, T: FromLua<'lua>> FromLua<'lua> for Option<T> {
@@ -1073,4 +1082,13 @@ impl<'lua, T: FromLua<'lua>> FromLua<'lua> for Option<T> {
             value => Ok(Some(T::from_lua(value, lua)?)),
         }
     }
+
+    #[inline]
+    unsafe fn from_stack(idx: c_int, lua: &'lua Lua) -> Result<Self> {
+        if ffi::lua_isnil(lua.state(), idx) != 0 {
+            Ok(None)
+        } else {
+            Ok(Some(T::from_stack(idx, lua)?))
+        }
+    }
 }

tests/conversion.rs

@@ -453,3 +453,21 @@ fn test_bstring_from_lua_buffer() -> Result<()> {
 
     Ok(())
 }
+
+#[test]
+fn test_option_into_from_lua() -> Result<()> {
+    let lua = Lua::new();
+
+    // Direct conversion
+    let v = Some(42);
+    let v2 = v.into_lua(&lua)?;
+    assert_eq!(v, v2.as_i32());
+
+    // Push into stack / get from stack
+    let f = lua.create_function(|_, v: Option<i32>| Ok(v))?;
+    assert_eq!(f.call::<_, Option<i32>>(Some(42))?, Some(42));
+    assert_eq!(f.call::<_, Option<i32>>(Option::<i32>::None)?, None);
+    assert_eq!(f.call::<_, Option<i32>>(())?, None);
+
+    Ok(())
+}