Derive DomObject with a proc macro

components/domobject_derive/Cargo.toml

@@ -0,0 +1,14 @@
+[package]
+name = "domobject_derive"
+version = "0.0.1"
+authors = ["The Servo Project Developers"]
+license = "MPL-2.0"
+publish = false
+
+[lib]
+path = "lib.rs"
+proc-macro = true
+
+[dependencies]
+syn = "0.10"
+quote = "0.3"

components/domobject_derive/lib.rs

@@ -0,0 +1,53 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+extern crate proc_macro;
+#[macro_use] extern crate quote;
+extern crate syn;
+
+#[proc_macro_derive(DomObject)]
+pub fn expand_token_stream(input: proc_macro::TokenStream) -> proc_macro::TokenStream {
+    expand_string(&input.to_string()).parse().unwrap()
+}
+
+fn expand_string(input: &str) -> String {
+    let type_ = syn::parse_macro_input(input).unwrap();
+
+    let first_field_name = if let syn::Body::Struct(syn::VariantData::Struct(ref fields)) = type_.body {
+        let first_field = fields.first().expect("#[derive(DomObject)] should not be applied on empty structs");
+        first_field.ident.as_ref().unwrap()
+    } else {
+        panic!("#[derive(DomObject)] should only be applied on proper structs")
+    };
+
+    let name = &type_.ident;
+    let (impl_generics, ty_generics, where_clause) = type_.generics.split_for_impl();
+
+    let tokens = quote! {
+        impl #impl_generics ::js::conversions::ToJSValConvertible for #name #ty_generics #where_clause {
+            #[allow(unsafe_code)]
+            unsafe fn to_jsval(&self,
+                                cx: *mut ::js::jsapi::JSContext,
+                                rval: ::js::jsapi::MutableHandleValue) {
+                let object = ::dom::bindings::reflector::DomObject::reflector(self).get_jsobject();
+                object.to_jsval(cx, rval)
+            }
+        }
+
+        impl #impl_generics ::dom::bindings::reflector::DomObject for #name #ty_generics #where_clause {
+            #[inline]
+            fn reflector(&self) -> &::dom::bindings::reflector::Reflector {
+                self.#first_field_name.reflector()
+            }
+        }
+
+        impl #impl_generics ::dom::bindings::reflector::MutDomObject for #name #ty_generics #where_clause {
+            fn init_reflector(&mut self, obj: *mut ::js::jsapi::JSObject) {
+                self.#first_field_name.init_reflector(obj);
+            }
+        }
+    };
+
+    tokens.to_string()
+}

components/plugins/jstraceable.rs

@@ -15,9 +15,7 @@ pub fn expand_dom_struct(cx: &mut ExtCtxt, sp: Span, _: &MetaItem, anno: Annotat
         item2.attrs.push(quote_attr!(cx, #[repr(C)]));
         item2.attrs.push(quote_attr!(cx, #[derive(JSTraceable)]));
         item2.attrs.push(quote_attr!(cx, #[derive(HeapSizeOf)]));
-
-        // The following attributes are only for internal usage
-        item2.attrs.push(quote_attr!(cx, #[_generate_reflector]));
+        item2.attrs.push(quote_attr!(cx, #[derive(DomObject)]));
         // #[dom_struct] gets consumed, so this lets us keep around a residue
         // Do NOT register a modifier/decorator on this attribute
         item2.attrs.push(quote_attr!(cx, #[_dom_struct_marker]));

components/plugins/lib.rs

@@ -34,8 +34,6 @@ use syntax::symbol::Symbol;
 /// Handles the auto-deriving for `#[derive(JSTraceable)]`
 pub mod jstraceable;
 pub mod lints;
-/// Autogenerates implementations of DomObject on DOM structs
-pub mod reflector;
 /// Utilities for writing plugins
 mod utils;
 
@@ -45,10 +43,6 @@ pub fn plugin_registrar(reg: &mut Registry) {
         Symbol::intern("dom_struct"),
         MultiModifier(box jstraceable::expand_dom_struct));
 
-    reg.register_syntax_extension(
-        Symbol::intern("_generate_reflector"),
-        MultiDecorator(box reflector::expand_reflector));
-
     reg.register_late_lint_pass(box lints::unrooted_must_root::UnrootedPass::new());
     reg.register_late_lint_pass(box lints::privatize::PrivatizePass);
     reg.register_late_lint_pass(box lints::inheritance_integrity::InheritancePass);

components/script/Cargo.toml

@@ -36,6 +36,7 @@ caseless = "0.1.0"
 cookie = {version = "0.2.5", features = ["serialize-rustc"]}
 cssparser = {version = "0.7", features = ["heap_size", "serde-serialization"]}
 devtools_traits = {path = "../devtools_traits"}
+domobject_derive = {path = "../domobject_derive"}
 encoding = "0.2"
 euclid = "0.10.1"
 fnv = "1.0"

components/script/dom/bindings/reflector.rs

@@ -83,8 +83,20 @@ pub trait DomObject {
     }
 }
 
+impl DomObject for Reflector {
+    fn reflector(&self) -> &Self {
+        self
+    }
+}
+
 /// A trait to initialize the `Reflector` for a DOM object.
 pub trait MutDomObject: DomObject {
     /// Initializes the Reflector
     fn init_reflector(&mut self, obj: *mut JSObject);
 }
+
+impl MutDomObject for Reflector {
+    fn init_reflector(&mut self, obj: *mut JSObject) {
+        self.set_jsobject(obj)
+    }
+}

components/script/lib.rs

@@ -39,6 +39,8 @@ extern crate core;
 #[macro_use]
 extern crate cssparser;
 extern crate devtools_traits;
+#[macro_use]
+extern crate domobject_derive;
 extern crate encoding;
 extern crate euclid;
 extern crate fnv;