"javascript:" urls: run in correct global

Make some changes to javascript scheme url evaluation to bring it
closer to
https://html.spec.whatwg.org/multipage/browsing-the-web.html#navigating-across-documents

- Evaluate the js before the page load so that it happens in the
  correct `window` global.
- If the result is not a string, the response should be a 204.

This required saving some data in load_data, since it's not
possible to modify the response at the point where we're evaluating
the js.

components/script/script_thread.rs

@@ -87,8 +87,8 @@ use script_runtime::{CommonScriptMsg, ScriptChan, ScriptThreadEventCategory};
 use script_runtime::{ScriptPort, StackRootTLS, get_reports, new_rt_and_cx};
 use script_traits::{CompositorEvent, ConstellationControlMsg};
 use script_traits::{DocumentActivity, DiscardBrowsingContext, EventResult};
-use script_traits::{InitialScriptState, LayoutMsg, LoadData, MouseButton, MouseEventType, MozBrowserEvent};
+use script_traits::{InitialScriptState, JsEvalResult, LayoutMsg, LoadData, MouseButton, MouseEventType};
-use script_traits::{NewLayoutInfo, ScriptToConstellationChan, ScriptMsg, UpdatePipelineIdReason};
+use script_traits::{MozBrowserEvent, NewLayoutInfo, ScriptToConstellationChan, ScriptMsg, UpdatePipelineIdReason};
 use script_traits::{ScriptThreadFactory, TimerEvent, TimerSchedulerMsg, TimerSource};
 use script_traits::{TouchEventType, TouchId, UntrustedNodeAddress, WindowSizeData, WindowSizeType};
 use script_traits::CompositorEvent::{KeyEvent, MouseButtonEvent, MouseMoveEvent, ResizeEvent};
@@ -1506,7 +1506,7 @@ impl ScriptThread {
                                            load_data.url.clone(),
                                            origin);
         if load_data.url.as_str() == "about:blank" {
-            self.start_page_load_about_blank(new_load);
+            self.start_page_load_about_blank(new_load, load_data.js_eval_result);
         } else {
             self.pre_page_load(new_load, load_data);
         }
@@ -1677,6 +1677,18 @@ impl ScriptThread {
         match idx {
             Some(idx) => {
                 let load = self.incomplete_loads.borrow_mut().remove(idx);
+
+                // https://html.spec.whatwg.org/multipage/#process-a-navigate-response
+                // 2. If response's status is 204 or 205, then abort these steps.
+                match metadata {
+                    Some(Metadata { status: Some((204 ... 205, _)), .. }) => {
+                        // TODO: This leaves the page in a broken state where you can't follow
+                        // other links. Fix this.
+                        return None;
+                    },
+                    _ => ()
+                };
+
                 metadata.map(|meta| self.load(meta, load))
             }
             None => {
@@ -2116,39 +2128,7 @@ impl ScriptThread {
         // Notify devtools that a new script global exists.
         self.notify_devtools(document.Title(), final_url.clone(), (incomplete.pipeline_id, None));
 
-        let is_javascript = incomplete.url.scheme() == "javascript";
+        let parse_input = DOMString::new();
-        let parse_input = if is_javascript {
-            use url::percent_encoding::percent_decode;
-
-            // Turn javascript: URL into JS code to eval, according to the steps in
-            // https://html.spec.whatwg.org/multipage/#javascript-protocol
-
-            // This slice of the URL’s serialization is equivalent to (5.) to (7.):
-            // Start with the scheme data of the parsed URL;
-            // append question mark and query component, if any;
-            // append number sign and fragment component if any.
-            let encoded = &incomplete.url[Position::BeforePath..];
-
-            // Percent-decode (8.) and UTF-8 decode (9.)
-            let script_source = percent_decode(encoded.as_bytes()).decode_utf8_lossy();
-
-            // Script source is ready to be evaluated (11.)
-            unsafe {
-                let _ac = JSAutoCompartment::new(self.get_cx(), window.reflector().get_jsobject().get());
-                rooted!(in(self.get_cx()) let mut jsval = UndefinedValue());
-                window.upcast::<GlobalScope>().evaluate_js_on_global_with_result(
-                    &script_source, jsval.handle_mut());
-                let strval = DOMString::from_jsval(self.get_cx(),
-                                                   jsval.handle(),
-                                                   StringificationBehavior::Empty);
-                match strval {
-                    Ok(ConversionResult::Success(s)) => s,
-                    _ => DOMString::new(),
-                }
-            }
-        } else {
-            DOMString::new()
-        };
 
         document.set_https_state(metadata.https_state);
 
@@ -2327,7 +2307,7 @@ impl ScriptThread {
     /// for the given pipeline (specifically the "navigate" algorithm).
     fn handle_navigate(&self, parent_pipeline_id: PipelineId,
                               browsing_context_id: Option<BrowsingContextId>,
-                              load_data: LoadData,
+                              mut load_data: LoadData,
                               replace: bool) {
         match browsing_context_id {
             Some(browsing_context_id) => {
@@ -2335,8 +2315,56 @@ impl ScriptThread {
                 if let Some(iframe) = iframe {
                     iframe.navigate_or_reload_child_browsing_context(Some(load_data), NavigationType::Regular, replace);
                 }
+
+                // TODO: Test javascript: urls in iframes
             }
             None => {
+                let is_javascript = load_data.url.scheme() == "javascript";
+                if is_javascript {
+                    use url::percent_encoding::percent_decode;
+
+                    // Turn javascript: URL into JS code to eval, according to the steps in
+                    // https://html.spec.whatwg.org/multipage/#javascript-protocol
+
+                    // This slice of the URL’s serialization is equivalent to (5.) to (7.):
+                    // Start with the scheme data of the parsed URL;
+                    // append question mark and query component, if any;
+                    // append number sign and fragment component if any.
+                    let encoded = &load_data.url[Position::BeforePath..];
+
+                    // Percent-decode (8.) and UTF-8 decode (9.)
+                    let script_source = percent_decode(encoded.as_bytes()).decode_utf8_lossy();
+
+                    // Script source is ready to be evaluated (11.)
+                    let window = self.documents.borrow().find_window(parent_pipeline_id);
+                    if let Some(window) = window {
+                        let _ac = JSAutoCompartment::new(self.get_cx(), window.reflector().get_jsobject().get());
+                        rooted!(in(self.get_cx()) let mut jsval = UndefinedValue());
+                        window.upcast::<GlobalScope>().evaluate_js_on_global_with_result(
+                            &script_source, jsval.handle_mut());
+
+                        load_data.js_eval_result = if jsval.get().is_string() {
+                            unsafe {
+                                let strval = DOMString::from_jsval(self.get_cx(),
+                                                                   jsval.handle(),
+                                                                   StringificationBehavior::Empty);
+                                match strval {
+                                    Ok(ConversionResult::Success(s)) => {
+                                        Some(JsEvalResult::Ok(String::from(s).as_bytes().to_vec()))
+                                    },
+                                    _ => None,
+                                }
+                            }
+                        } else {
+                            Some(JsEvalResult::NoContent)
+                        };
+                    }
+                }
+
+                if is_javascript {
+                    load_data.url = ServoUrl::parse("about:blank").unwrap();
+                }
+
                 self.script_sender
                     .send((parent_pipeline_id, ScriptMsg::LoadUrl(load_data, replace)))
                     .unwrap();
@@ -2375,7 +2403,7 @@ impl ScriptThread {
     /// argument until a notification is received that the fetch is complete.
     fn pre_page_load(&self, incomplete: InProgressLoad, load_data: LoadData) {
         let id = incomplete.pipeline_id.clone();
-        let mut req_init = RequestInit {
+        let req_init = RequestInit {
             url: load_data.url.clone(),
             method: load_data.method,
             destination: Destination::Document,
@@ -2391,10 +2419,6 @@ impl ScriptThread {
             .. RequestInit::default()
         };
 
-        if req_init.url.scheme() == "javascript" {
-            req_init.url = ServoUrl::parse("about:blank").unwrap();
-        }
-
         let context = ParserContext::new(id, load_data.url);
         self.incomplete_parser_contexts.borrow_mut().push((id, context));
 
@@ -2434,7 +2458,7 @@ impl ScriptThread {
 
     /// Synchronously fetch `about:blank`. Stores the `InProgressLoad`
     /// argument until a notification is received that the fetch is complete.
-    fn start_page_load_about_blank(&self, incomplete: InProgressLoad) {
+    fn start_page_load_about_blank(&self, incomplete: InProgressLoad, js_eval_result: Option<JsEvalResult>) {
         let id = incomplete.pipeline_id;
 
         self.incomplete_loads.borrow_mut().push(incomplete);
@@ -2444,8 +2468,20 @@ impl ScriptThread {
 
         let mut meta = Metadata::default(url);
         meta.set_content_type(Some(&mime!(Text / Html)));
+
+        // If this page load is the result of a javascript scheme url, map
+        // the evaluation result into a response.
+        let chunk = match js_eval_result {
+            Some(JsEvalResult::Ok(content)) => content,
+            Some(JsEvalResult::NoContent) => {
+                meta.status = Some((204, b"No Content".to_vec()));
+                vec![]
+            },
+            None => vec![]
+        };
+
         context.process_response(Ok(FetchMetadata::Unfiltered(meta)));
-        context.process_response_chunk(vec![]);
+        context.process_response_chunk(chunk);
         context.process_response_eof(Ok(()));
     }
 

components/script_traits/lib.rs

@@ -146,12 +146,24 @@ pub struct LoadData {
     pub headers: Headers,
     /// The data.
     pub data: Option<Vec<u8>>,
+    /// The result of evaluating a javascript scheme url.
+    pub js_eval_result: Option<JsEvalResult>,
     /// The referrer policy.
     pub referrer_policy: Option<ReferrerPolicy>,
     /// The referrer URL.
     pub referrer_url: Option<ServoUrl>,
 }
 
+/// The result of evaluating a javascript scheme url.
+#[derive(Clone, Debug, Deserialize, Serialize)]
+pub enum JsEvalResult {
+    /// The js evaluation had a non-string result, 204 status code.
+    /// https://html.spec.whatwg.org/multipage/#navigate 12.11
+    NoContent,
+    /// The js evaluation had a string result.
+    Ok(Vec<u8>)
+}
+
 impl LoadData {
     /// Create a new `LoadData` object.
     pub fn new(url: ServoUrl,
@@ -165,6 +177,7 @@ impl LoadData {
             method: Method::Get,
             headers: Headers::new(),
             data: None,
+            js_eval_result: None,
             referrer_policy: referrer_policy,
             referrer_url: referrer_url,
         }