Don't require an owned value for property setters.

I wrote this as I was thinking about #1180, but not sure it's worth the
complexity. If you think there are some other things that might use it,
please go ahead and merge it, otherwise feel free to close :)

Author: emilio

zbus/src/fdo/properties.rs

@@ -62,7 +62,7 @@ impl Properties {
         &self,
         interface_name: InterfaceName<'_>,
         property_name: &str,
-        value: Value<'_>,
+        value: &Value<'_>,
         #[zbus(object_server)] server: &ObjectServer,
         #[zbus(connection)] connection: &Connection,
         #[zbus(header)] header: Header<'_>,
@@ -79,7 +79,7 @@ impl Properties {
 
         match iface.instance.read().await.set(
             property_name,
-            &value,
+            value,
             server,
             connection,
             Some(&header),

zbus/src/proxy/mod.rs

@@ -810,7 +810,7 @@ impl<'a> Proxy<'a> {
         T: 't + Into<Value<'t>>,
     {
         self.properties_proxy()
-            .set(self.inner.interface.as_ref(), property_name, value.into())
+            .set(self.inner.interface.as_ref(), property_name, &value.into())
             .await
     }
 

zbus_macros/src/iface.rs

@@ -11,7 +11,7 @@ use syn::{
     ImplItem, ImplItemFn, ItemImpl,
     Lit::Str,
     Meta, MetaNameValue, PatType, PathArguments, ReturnType, Signature, Token, Type, TypePath,
-    Visibility,
+    TypeReference, Visibility,
 };
 use zvariant_utils::{case, def_attrs};
 
@@ -983,6 +983,18 @@ pub fn expand(args: Punctuated<Meta, Token![,]>, mut input: ItemImpl) -> syn::Re
     })
 }
 
+fn maybe_unref_ty(ty: &Type) -> Option<&Type> {
+    fn should_unref(v: &TypeReference) -> bool {
+        // &str is special and we can deserialize to it, unlike other reference types.
+        !matches!(*v.elem, Type::Path(ref p) if p.path.is_ident("str"))
+    }
+
+    match *ty {
+        Type::Reference(ref v) if should_unref(v) => Some(&v.elem),
+        _ => None,
+    }
+}
+
 fn get_args_from_inputs(
     inputs: &[PatType],
     method_type: MethodType,
@@ -1071,7 +1083,7 @@ fn get_args_from_inputs(
                 };
             } else {
                 args_names.push(pat_ident(input).unwrap());
-                tys.push(&input.ty);
+                tys.push(&*input.ty);
             }
         }
 
@@ -1085,15 +1097,36 @@ fn get_args_from_inputs(
             _ => (
                 quote! { let hdr = message.header(); },
                 quote! { let msg_body = message.body(); },
-                quote! {
-                    let (#(#args_names),*): (#(#tys),*) =
-                        match msg_body.deserialize() {
-                            ::std::result::Result::Ok(r) => r,
-                            ::std::result::Result::Err(e) => {
-                                let err = <#zbus::fdo::Error as ::std::convert::From<_>>::from(e);
-                                return connection.reply_dbus_error(&hdr, err).await;
+                {
+                    let mut unrefed_indices = vec![];
+                    let owned_tys = tys
+                        .iter()
+                        .enumerate()
+                        .map(|(i, ty)| {
+                            let owned = maybe_unref_ty(ty);
+                            if owned.is_some() {
+                                unrefed_indices.push(i);
                             }
-                        };
+                            owned.unwrap_or(ty)
+                        })
+                        .collect::<Vec<_>>();
+                    let mut q = quote! {
+                        let (#(#args_names),*): (#(#owned_tys),*) =
+                            match msg_body.deserialize() {
+                                ::std::result::Result::Ok(r) => r,
+                                ::std::result::Result::Err(e) => {
+                                    let err = <#zbus::fdo::Error as ::std::convert::From<_>>::from(e);
+                                    return connection.reply_dbus_error(&hdr, err).await;
+                                }
+                            };
+                    };
+                    for index in unrefed_indices {
+                        let arg_name = &args_names[index];
+                        q.extend(quote! {
+                            let #arg_name = &#arg_name;
+                        });
+                    }
+                    q
                 },
             ),
         };