servo: Merge #2091 - Make GetCallableProperty more rustic (from Ms2ger:GetCallableProperty); r=jdm

Source-Repo: https://github.com/servo/servo
Source-Revision: 4683788600a8acf0f77d81117c6b1bcf1a1a618f

servo/src/components/script/dom/bindings/callback.rs

@@ -5,7 +5,7 @@
 use dom::bindings::utils::Reflectable;
 use js::jsapi::{JSContext, JSObject, JS_WrapObject, JS_ObjectIsCallable};
 use js::jsapi::{JS_GetProperty, JSTracer, JS_CallTracer};
-use js::jsval::JSVal;
+use js::jsval::{JSVal, UndefinedValue};
 use js::JSTRACE_OBJECT;
 
 use std::cast;
@@ -61,20 +61,20 @@ impl CallbackInterface {
         }
     }
 
-    pub fn GetCallableProperty(&self, cx: *JSContext, name: *libc::c_char, callable: &mut JSVal) -> bool {
+    pub fn GetCallableProperty(&self, cx: *JSContext, name: &str) -> Result<JSVal, ()> {
+        let mut callable = UndefinedValue();
         unsafe {
-            if JS_GetProperty(cx, self.callback, name, &*callable) == 0 {
-                return false;
+            if name.to_c_str().with_ref(|name| JS_GetProperty(cx, self.callback, name, &mut callable as *mut JSVal as *JSVal)) == 0 {
+                return Err(());
             }
 
             if !callable.is_object() ||
                JS_ObjectIsCallable(cx, callable.to_object()) == 0 {
                 //ThrowErrorMessage(cx, MSG_NOT_CALLABLE, description.get());
-                return false;
+                return Err(());
             }
-
-            return true;
         }
+        Ok(callable)
     }
 }
 

servo/src/components/script/dom/bindings/codegen/CodegenRust.py

@@ -5312,19 +5312,19 @@ class CallbackOperationBase(CallbackMethod):
             "methodName": self.methodName
             }
         getCallableFromProp = string.Template(
-                'if "${methodName}".to_c_str().with_ref(|name| !self.parent.GetCallableProperty(cx, name, &mut callable)) {\n'
-                '  return${errorReturn};\n'
-                '}\n').substitute(replacements)
+                'match self.parent.GetCallableProperty(cx, "${methodName}") {\n'
+                '  Err(_) => return${errorReturn},\n'
+                '  Ok(callable) => callable,\n'
+                '}').substitute(replacements)
         if not self.singleOperation:
             return 'JS::Rooted<JS::Value> callable(cx);\n' + getCallableFromProp
         return (
             'let isCallable = unsafe { JS_ObjectIsCallable(cx, self.parent.callback) != 0 };\n'
-            'let mut callable = UndefinedValue();\n'
-            'if isCallable {\n'
-            '  callable = unsafe { ObjectValue(&*self.parent.callback) };\n'
-            '} else {\n'
-            '%s'
-            '}\n' % CGIndenter(CGGeneric(getCallableFromProp)).define())
+            'let callable =\n' +
+            CGIndenter(
+                CGIfElseWrapper('isCallable',
+                                CGGeneric('unsafe { ObjectValue(&*self.parent.callback) }'),
+                                CGGeneric(getCallableFromProp))).define() + ';\n')
 
 class CallbackOperation(CallbackOperationBase):
     """