Let protocol handlers decide if they are fetchable (#33573)

This adds a 'is_fetchable()' method on the ProtocolHandler trait that is then used in the fetch code.
The 'data:' protocol handler is updated to return true instead of hardcoding the scheme comparison, as well
as the 'urlinfo:' handler since it's just a testing one.

Signed-off-by: webbeef <me@webbeef.org>

components/net/fetch/methods.rs

@@ -274,10 +274,12 @@ pub async fn main_fetch(
 
     // Step 12.
 
+    let current_url = request.current_url();
+    let current_scheme = current_url.scheme();
+
     let mut response = match response {
         Some(res) => res,
         None => {
-            let current_url = request.current_url();
             let same_origin = if let Origin::Origin(ref origin) = request.origin {
                 *origin == current_url.origin()
             } else {
@@ -285,8 +287,8 @@ pub async fn main_fetch(
             };
 
             if (same_origin && !cors_flag) ||
-                current_url.scheme() == "data" ||
-                current_url.scheme() == "chrome" ||
+                current_scheme == "chrome" ||
+                context.protocols.is_fetchable(current_scheme) ||
                 matches!(
                     request.mode,
                     RequestMode::Navigate | RequestMode::WebSocket { .. }
@@ -312,7 +314,7 @@ pub async fn main_fetch(
                     // Substep 3. Return the result of running scheme fetch given fetchParams.
                     scheme_fetch(request, cache, target, done_chan, context).await
                 }
-            } else if !matches!(current_url.scheme(), "http" | "https") {
+            } else if !matches!(current_scheme, "http" | "https") {
                 Response::network_error(NetworkError::Internal("Non-http scheme".into()))
             } else if request.use_cors_preflight ||
                 (request.unsafe_request &&
@@ -494,7 +496,7 @@ pub async fn main_fetch(
     }
 
     // Step 21.
-    if request.body.is_some() && matches!(request.current_url().scheme(), "http" | "https") {
+    if request.body.is_some() && matches!(current_scheme, "http" | "https") {
         // XXXManishearth: We actually should be calling process_request
         // in http_network_fetch. However, we can't yet follow the request
         // upload progress, so I'm keeping it here for now and pretending

components/net/protocols/data.rs

@@ -54,4 +54,8 @@ impl ProtocolHandler for DataProtocolHander {
 
         Box::pin(std::future::ready(response))
     }
+
+    fn is_fetchable(&self) -> bool {
+        true
+    }
 }

components/net/protocols/mod.rs

@@ -29,12 +29,24 @@ use file::FileProtocolHander;
 static FORBIDDEN_SCHEMES: [&str; 4] = ["http", "https", "chrome", "about"];
 
 pub trait ProtocolHandler: Send + Sync {
+    /// Triggers the load of a resource for this protocol and returns a future
+    /// that will produce a Response. Even if the protocol is not backed by a
+    /// http endpoint, it is recommended to a least provide:
+    /// - A relevant status code.
+    /// - A Content Type.
     fn load(
         &self,
         request: &mut Request,
         done_chan: &mut DoneChannel,
         context: &FetchContext,
     ) -> Pin<Box<dyn Future<Output = Response> + Send>>;
+
+    /// Specify if resources served by that protocol can be retrieved
+    /// with `fetch()` without no-cors mode to allow the caller direct
+    /// access to the resource content.
+    fn is_fetchable(&self) -> bool {
+        false
+    }
 }
 
 #[derive(Default)]
@@ -80,6 +92,13 @@ impl ProtocolRegistry {
             self.handlers.entry(scheme).or_insert(handler);
         }
     }
+
+    pub fn is_fetchable(&self, scheme: &str) -> bool {
+        self.handlers
+            .get(scheme)
+            .map(|handler| handler.is_fetchable())
+            .unwrap_or(false)
+    }
 }
 
 pub fn range_not_satisfiable_error(response: &mut Response) {

ports/servoshell/desktop/protocols/urlinfo.rs

@@ -43,4 +43,8 @@ impl ProtocolHandler for UrlInfoProtocolHander {
 
         Box::pin(std::future::ready(response))
     }
+
+    fn is_fetchable(&self) -> bool {
+        true
+    }
 }