Infrastructure for synchronous script loading

This implements the parts of the "prepare a script element" algorithm that are
required for synchronous scripts.  It also adds some infrastructure for future
support of the `async` and `defer` attributes.

1 files changed, 135 insertions, 7 deletions

diff --git a/components/script/dom/htmlscriptelement.rs b/components/script/dom/htmlscriptelement.rs
index b970596fbdd..9c20435f67a 100644
--- a/components/script/dom/htmlscriptelement.rs
+++ b/components/script/dom/htmlscriptelement.rs
@@ -14,13 +14,35 @@ use dom::document::Document;
 use dom::element::{HTMLScriptElementTypeId, Element, AttributeHandlers};
 use dom::eventtarget::{EventTarget, NodeTargetTypeId};
 use dom::htmlelement::HTMLElement;
-use dom::node::{Node, NodeHelpers, ElementNodeTypeId};
+use dom::node::{Node, NodeHelpers, ElementNodeTypeId, window_from_node};
+use dom::window::WindowHelpers;
 
+use encoding::all::UTF_8;
+use encoding::types::{Encoding, DecodeReplace};
+use servo_net::resource_task::load_whole_resource;
 use servo_util::str::{DOMString, HTML_SPACE_CHARACTERS, StaticStringVec};
+use std::cell::Cell;
+use url::UrlParser;
 
 #[dom_struct]
 pub struct HTMLScriptElement {
     htmlelement: HTMLElement,
+
+    /// https://html.spec.whatwg.org/multipage/scripting.html#already-started
+    already_started: Cell<bool>,
+
+    /// https://html.spec.whatwg.org/multipage/scripting.html#parser-inserted
+    parser_inserted: Cell<bool>,
+
+    /// https://html.spec.whatwg.org/multipage/scripting.html#non-blocking
+    ///
+    /// (currently unused)
+    non_blocking: Cell<bool>,
+
+    /// https://html.spec.whatwg.org/multipage/scripting.html#ready-to-be-parser-executed
+    ///
+    /// (currently unused)
+    ready_to_be_parser_executed: Cell<bool>,
 }
 
 impl HTMLScriptElementDerived for EventTarget {
@@ -30,22 +52,30 @@ impl HTMLScriptElementDerived for EventTarget {
 }
 
 impl HTMLScriptElement {
-    fn new_inherited(localName: DOMString, prefix: Option<DOMString>, document: JSRef<Document>) -> HTMLScriptElement {
+    fn new_inherited(localName: DOMString, prefix: Option<DOMString>, document: JSRef<Document>,
+                     parser_inserted: bool) -> HTMLScriptElement {
         HTMLScriptElement {
-            htmlelement: HTMLElement::new_inherited(HTMLScriptElementTypeId, localName, prefix, document)
+            htmlelement: HTMLElement::new_inherited(HTMLScriptElementTypeId, localName, prefix, document),
+            already_started: Cell::new(false),
+            parser_inserted: Cell::new(parser_inserted),
+            non_blocking: Cell::new(!parser_inserted),
+            ready_to_be_parser_executed: Cell::new(false),
         }
     }
 
     #[allow(unrooted_must_root)]
-    pub fn new(localName: DOMString, prefix: Option<DOMString>, document: JSRef<Document>) -> Temporary<HTMLScriptElement> {
-        let element = HTMLScriptElement::new_inherited(localName, prefix, document);
+    pub fn new(localName: DOMString, prefix: Option<DOMString>, document: JSRef<Document>,
+               parser_inserted: bool) -> Temporary<HTMLScriptElement> {
+        let element = HTMLScriptElement::new_inherited(localName, prefix, document, parser_inserted);
         Node::reflect_node(box element, document, HTMLScriptElementBinding::Wrap)
     }
 }
 
 pub trait HTMLScriptElementHelpers {
-    /// Prepare a script (<http://www.whatwg.org/html/#prepare-a-script>),
-    /// steps 6 and 7.
+    /// Prepare a script (<http://www.whatwg.org/html/#prepare-a-script>)
+    fn prepare(self);
+
+    /// Prepare a script, steps 6 and 7.
     fn is_javascript(self) -> bool;
 }
 
@@ -71,6 +101,104 @@ static SCRIPT_JS_MIMES: StaticStringVec = &[
 ];
 
 impl<'a> HTMLScriptElementHelpers for JSRef<'a, HTMLScriptElement> {
+    fn prepare(self) {
+        // https://html.spec.whatwg.org/multipage/scripting.html#prepare-a-script
+        // Step 1.
+        if self.already_started.get() {
+            return;
+        }
+        // Step 2.
+        let was_parser_inserted = self.parser_inserted.get();
+        self.parser_inserted.set(false);
+
+        // Step 3.
+        let element: JSRef<Element> = ElementCast::from_ref(self);
+        if was_parser_inserted && element.has_attribute(&atom!("async")) {
+            self.non_blocking.set(true);
+        }
+        // Step 4.
+        let text = self.Text();
+        if text.len() == 0 && !element.has_attribute(&atom!("src")) {
+            return;
+        }
+        // Step 5.
+        let node: JSRef<Node> = NodeCast::from_ref(self);
+        if !node.is_in_doc() {
+            return;
+        }
+        // Step 6, 7.
+        if !self.is_javascript() {
+            return;
+        }
+        // Step 8.
+        if was_parser_inserted {
+            self.parser_inserted.set(true);
+            self.non_blocking.set(false);
+        }
+        // Step 9.
+        self.already_started.set(true);
+
+        // Step 10.
+        // TODO: If the element is flagged as "parser-inserted", but the element's node document is
+        // not the Document of the parser that created the element, then abort these steps.
+
+        // Step 11.
+        // TODO: If scripting is disabled for the script element, then the user agent must abort
+        // these steps at this point. The script is not executed.
+
+        // Step 12.
+        // TODO: If the script element has an `event` attribute and a `for` attribute, then run
+        // these substeps...
+
+        // Step 13.
+        // TODO: If the script element has a `charset` attribute, then let the script block's
+        // character encoding for this script element be the result of getting an encoding from the
+        // value of the `charset` attribute.
+
+        // Step 14 and 15.
+        // TODO: Add support for the `defer` and `async` attributes.  (For now, we fetch all
+        // scripts synchronously and execute them immediately.)
+        let window = window_from_node(self).root();
+        let page = window.page();
+        let base_url = page.get_url();
+
+        let (source, url) = match element.get_attribute(ns!(""), &atom!("src")).root() {
+            Some(src) => {
+                if src.deref().Value().is_empty() {
+                    // TODO: queue a task to fire a simple event named `error` at the element
+                    return;
+                }
+                match UrlParser::new().base_url(&base_url).parse(src.deref().Value().as_slice()) {
+                    Ok(url) => {
+                        // TODO: Do a potentially CORS-enabled fetch with the mode being the current
+                        // state of the element's `crossorigin` content attribute, the origin being
+                        // the origin of the script element's node document, and the default origin
+                        // behaviour set to taint.
+                        match load_whole_resource(&page.resource_task, url) {
+                            Ok((metadata, bytes)) => {
+                                // TODO: use the charset from step 13.
+                                let source = UTF_8.decode(bytes.as_slice(), DecodeReplace).unwrap();
+                                (source, metadata.final_url)
+                            }
+                            Err(_) => {
+                                error!("error loading script {}", src.deref().Value());
+                                return;
+                            }
+                        }
+                    }
+                    Err(_) => {
+                        // TODO: queue a task to fire a simple event named `error` at the element
+                        error!("error parsing URL for script {}", src.deref().Value());
+                        return;
+                    }
+                }
+            }
+            None => (text, base_url)
+        };
+
+        window.evaluate_script_with_result(source.as_slice(), url.serialize().as_slice());
+    }
+
     fn is_javascript(self) -> bool {
         let element: JSRef<Element> = ElementCast::from_ref(self);
         match element.get_attribute(ns!(""), &atom!("type")).root().map(|s| s.Value()) {