✨ zm: add no_spawn attribute on interface

Signed-off-by: Marc-André Lureau <[email protected]>

zbus_macros/src/iface.rs

@@ -18,7 +18,8 @@ pub mod old {
 
         pub TraitAttributes("trait") {
             interface str,
-            name str
+            name str,
+            no_spawn none
         };
 
         pub MethodAttributes("method") {
@@ -39,7 +40,8 @@ def_attrs! {
 
     pub TraitAttributes("trait") {
         interface str,
-        name str
+        name str,
+        no_spawn none
     };
 
     pub MethodAttributes("method") {
@@ -300,22 +302,24 @@ pub fn expand<T: AttrParse + Into<TraitAttrs>, M: AttrParse + Into<MethodAttrs>>
         _ => return Err(Error::new_spanned(&input.self_ty, "Invalid type")),
     };
 
-    let iface_name =
-        {
-            let (name, interface) = match T::parse_nested_metas(&args)?.into() {
-                TraitAttrs::New(new) => (new.name, new.interface),
-                TraitAttrs::Old(old) => (old.name, old.interface),
-            };
+    let (iface_name, with_spawn) = {
+        let (name, interface, no_spawn) = match T::parse_nested_metas(&args)?.into() {
+            TraitAttrs::New(new) => (new.name, new.interface, new.no_spawn),
+            TraitAttrs::Old(old) => (old.name, old.interface, old.no_spawn),
+        };
 
+        let name =
             match (name, interface) {
                 (Some(name), None) | (None, Some(name)) => name,
                 (None, None) => format!("org.freedesktop.{ty}"),
                 (Some(_), Some(_)) => return Err(syn::Error::new(
                     input.span(),
                     "`name` and `interface` attributes should not be specified at the same time",
                 )),
-            }
-        };
+            };
+
+        (name, !no_spawn)
+    };
 
     // Store parsed information about each method
     let mut methods = vec![];
@@ -713,6 +717,10 @@ pub fn expand<T: AttrParse + Into<TraitAttrs>, M: AttrParse + Into<MethodAttrs>>
                 #zbus::names::InterfaceName::from_static_str_unchecked(#iface_name)
             }
 
+            fn with_spawn(&self) -> bool {
+                #with_spawn
+            }
+
             async fn get(
                 &self,
                 property_name: &str,

zbus_macros/src/lib.rs

@@ -215,6 +215,15 @@ pub fn dbus_proxy(attr: TokenStream, item: TokenStream) -> TokenStream {
 /// properties or signal depending on the item attributes. It will implement the [`Interface`] trait
 /// `for T` on your behalf, to handle the message dispatching and introspection support.
 ///
+/// The trait accepts the `interface` attributes:
+///
+/// * `name` - the D-Bus interface name
+///
+/// * `no_spawn` - Do not spawn async tasks to call the methods. By default, zbus will spawn a task
+///   for each method call. This may result in methods being handled out of order and may not be the
+///   expected or desired behaviour. Note that D-Bus has currently not stated explicitely message
+///   ordering guarantees (see also https://gitlab.freedesktop.org/dbus/dbus/-/issues/179).
+///
 /// The methods accepts the `interface` attributes:
 ///
 /// * `name` - override the D-Bus name (pascal case form of the method by default)

zbus_macros/tests/tests.rs

@@ -139,7 +139,7 @@ fn test_interface() {
     #[derive(Serialize, Deserialize, Type, Value)]
     struct MyCustomPropertyType(u32);
 
-    #[interface(name = "org.freedesktop.zbus.Test")]
+    #[interface(name = "org.freedesktop.zbus.Test", no_spawn)]
     impl<T: 'static> Test<T>
     where
         T: serde::ser::Serialize + zbus::zvariant::Type + Send + Sync,