Implement Document's 'body' attribute

Implement Document's 'body' attribute (getter and setter). Proper
implementation of setter requires Node::ReplaceChild(), which is
currently a stub and will be done on a later step.

This patch is for:
https://github.com/mozilla/servo/issues/1428

src/components/script/dom/bindings/codegen/Bindings.conf

@@ -156,6 +156,7 @@ DOMInterfaces = {
         'createElement',
         'createTextNode',
         'title',
+        'body',
     ],
 },
 

src/components/script/dom/bindings/codegen/Document.webidl

@@ -100,7 +100,7 @@ partial interface Document {
            [SetterThrows]
            attribute DOMString title;
   //          attribute DOMString dir;
-  //(HTML only)         attribute HTMLElement? body;
+           attribute HTMLElement? body;
   //(HTML only)readonly attribute HTMLHeadElement? head;
   //(HTML only)readonly attribute HTMLCollection images;
   //(HTML only)readonly attribute HTMLCollection embeds;

src/components/script/dom/document.rs

@@ -5,12 +5,12 @@
 use dom::comment::Comment;
 use dom::bindings::codegen::DocumentBinding;
 use dom::bindings::utils::{Reflectable, Reflector, Traceable, reflect_dom_object};
-use dom::bindings::utils::{ErrorResult, Fallible, NotSupported, InvalidCharacter};
+use dom::bindings::utils::{ErrorResult, Fallible, NotSupported, InvalidCharacter, HierarchyRequest};
 use dom::bindings::utils::DOMString;
 use dom::bindings::utils::{xml_name_type, InvalidXMLName};
 use dom::documentfragment::DocumentFragment;
 use dom::element::{Element};
-use dom::element::{HTMLHeadElementTypeId, HTMLTitleElementTypeId};
+use dom::element::{HTMLHtmlElementTypeId, HTMLHeadElementTypeId, HTMLTitleElementTypeId, HTMLBodyElementTypeId, HTMLFrameSetElementTypeId};
 use dom::event::{AbstractEvent, Event};
 use dom::htmlcollection::HTMLCollection;
 use dom::htmldocument::HTMLDocument;
@@ -295,6 +295,63 @@ impl Document {
         Ok(())
     }
 
+    fn get_html_element(&self) -> Option<AbstractNode> {
+        do self.GetDocumentElement().filtered |root| {
+            match root.type_id() {
+                ElementNodeTypeId(HTMLHtmlElementTypeId) => true,
+                _ => false
+            }
+        }
+    }
+
+    pub fn GetBody(&self, _: AbstractDocument) -> Option<AbstractNode> {
+        match self.get_html_element() {
+            None => None,
+            Some(root) => {
+                do root.children().find |child| {
+                    match child.type_id() {
+                        ElementNodeTypeId(HTMLBodyElementTypeId) |
+                        ElementNodeTypeId(HTMLFrameSetElementTypeId) => true,
+                        _ => false
+                    }
+                }
+            }
+        }
+    }
+
+    // http://www.whatwg.org/specs/web-apps/current-work/#dom-document-body
+    pub fn SetBody(&self, abstract_self: AbstractDocument, new_body: Option<AbstractNode>) -> ErrorResult {
+        // Step 1.
+        match new_body {
+            Some(node) => {
+                match node.type_id() {
+                    ElementNodeTypeId(HTMLBodyElementTypeId) | ElementNodeTypeId(HTMLFrameSetElementTypeId) => {}
+                    _ => return Err(HierarchyRequest)
+                }
+            }
+            None => return Err(HierarchyRequest)
+        }
+
+        // Step 2.
+        let old_body: Option<AbstractNode> = self.GetBody(abstract_self);
+        if old_body == new_body {
+            return Ok(());
+        }
+
+        // Step 3.
+        match self.get_html_element() {
+            // Step 4.
+            None => return Err(HierarchyRequest),
+            Some(root) => {
+                match old_body {
+                    Some(child) => { root.ReplaceChild(new_body.unwrap(), child); }
+                    None => { root.AppendChild(new_body.unwrap()); }
+                }
+            }
+        }
+        Ok(())
+    }
+
     pub fn GetElementsByName(&self, name: DOMString) -> @mut HTMLCollection {
         self.createHTMLCollection(|elem|
             elem.get_attr(None, "name").is_some() && eq_slice(elem.get_attr(None, "name").unwrap(), name))

src/components/script/dom/node.rs

@@ -496,6 +496,10 @@ impl AbstractNode {
         self.node().AppendChild(self, node)
     }
 
+    pub fn ReplaceChild(self, node: AbstractNode, child: AbstractNode) -> Fallible<AbstractNode> {
+        self.mut_node().ReplaceChild(node, child)
+    }
+
     pub fn RemoveChild(self, node: AbstractNode) -> Fallible<AbstractNode> {
         self.node().RemoveChild(self, node)
     }

src/test/html/content/test_document_body.html

@@ -0,0 +1,75 @@
+<html>
+    <head>
+        <script src="harness.js"></script>
+    </head>
+    <body>
+        <script>
+            // test1: existing document's body
+            {
+                isnot(document.body, null, "test1-0, existing document's body");
+                is_a(document.body, HTMLBodyElement, "test1-1, exising document's body");
+                is(document.body && document.body.tagName, "BODY", "test1-2, existing document's body");
+            }
+
+            /* TODO: Depends on https://github.com/mozilla/servo/issues/1430
+            // test2: replace document's body with new body
+            {
+                let new_body = document.createElement("body");
+                isnot(new_body, null, "test2-0, replace document's body with new body");
+                document.body = new_body;
+                is(new_body, document.body, "test2-1, replace document's body with new body");
+            }
+
+            // test3: replace document's body with new frameset
+            {
+                let new_frameset = document.createElement("frameset");
+                isnot(new_frameset, null, "test2-0, replace document's body with new frameset");
+                document.body = new_frameset;
+                is(new_frameset, document.body, "test2-1, replace document's body with new frameset");
+            }
+            */
+
+            // test4: append an invalid element to a new document
+            {
+                let new_document = new Document();
+                new_document.appendChild(new_document.createElement("html"));
+                let new_div = new_document.createElement("div");
+
+                isnot(new_div, null, "test4-0, append an invalid element to a new document");
+
+                new_document.body = new_div;
+                is(new_document.body, null, "test4-1, append an invalid element to a new document");
+            }
+
+            // test5: append body to a new document
+            {
+                let new_document = new Document();
+                new_document.appendChild(new_document.createElement("html"));
+                let new_body = new_document.createElement("body");
+
+                isnot(new_body, null, "test5-0, append body to a new document");
+                is_a(new_body, HTMLBodyElement, "test5-1, append body to a new document");
+                is(new_body && new_body.tagName, "BODY", "test5-2, append body to a new document");
+
+                new_document.body = new_body;
+                is(new_document.body, new_body, "test5-3, append body to a new document");
+            }
+
+            // test6: append frameset to a new document
+            {
+                let new_document = new Document();
+                new_document.appendChild(new_document.createElement("html"));
+                let new_frameset = new_document.createElement("frameset");
+
+                isnot(new_frameset, null, "test6-0, append frameset to a new document");
+                is_a(new_frameset, HTMLFrameSetElement, "test6-1, append frameset to a new document");
+                is(new_frameset && new_frameset.tagName, "FRAMESET", "test6-2, append frameset to a new document");
+
+                new_document.body = new_frameset;
+                is(new_document.body, new_frameset, "test6-3, append frameset to a new document");
+            }
+
+            finish();
+        </script>
+    </body>
+</html>