Bug 1940382 - Part 3: Don't preload json modules. r=dom-core,necko-reviewers,valentin,farre

Implement whatwg/html#10212

Disallow preloading for "json".
https://html.spec.whatwg.org/#translate-a-preload-destination

And add mime-type check for JSON files.

Differential Revision: https://phabricator.services.mozilla.com/D234849

Author: allstarschh

dom/html/HTMLLinkElement.cpp

@@ -481,6 +481,27 @@ void HTMLLinkElement::
         return;
       }
 
+      // https://html.spec.whatwg.org/#translate-a-preload-destination
+      // If destination is not "fetch", "font", "image", "script", "style", or
+      // "track", then return null.
+      int16_t asValue = asAttr.GetEnumValue();
+      if (asValue != net::DESTINATION_FETCH &&
+          asValue != net::DESTINATION_FONT &&
+          asValue != net::DESTINATION_IMAGE &&
+          asValue != net::DESTINATION_SCRIPT &&
+          asValue != net::DESTINATION_STYLE &&
+          asValue != net::DESTINATION_TRACK) {
+        // TODO: Currently the spec doesn't define an event handler to be called
+        // , but this is under discussion.
+        // See: https://github.com/whatwg/html/issues/10940
+        //
+        // Post a "load" event here to match the legacy behavior.
+        RefPtr<AsyncEventDispatcher> asyncDispatcher = new AsyncEventDispatcher(
+            this, u"load"_ns, CanBubble::eNo, ChromeOnlyDispatch::eNo);
+        asyncDispatcher->PostDOMEvent();
+        return;
+      }
+
       StartPreload(policyType);
       return;
     }

netwerk/base/nsNetUtil.cpp

@@ -3995,6 +3995,9 @@ bool CheckPreloadAttrs(const nsAttrValue& aAs, const nsAString& aType,
   if (policyType == nsIContentPolicy::TYPE_STYLESHEET) {
     return type.EqualsASCII("text/css");
   }
+  if (policyType == nsIContentPolicy::TYPE_JSON) {
+    return nsContentUtils::IsJsonMimeType(type);
+  }
   return false;
 }
 

testing/web-platform/meta/fetch/api/request/destination/fetch-destination.https.html.ini

@@ -3,12 +3,6 @@
   expected:
     if (os == "win") and debug: [OK, ERROR]
     if (os == "android") and not debug: [OK, ERROR]
-  [HTMLLinkElement with rel=preload and as=audio fetches with a "audio" Request.destination]
-    expected: FAIL
-
-  [HTMLLinkElement with rel=preload and as=video fetches with a "video" Request.destination]
-    expected: FAIL
-
   [HTMLLinkElement with rel=preload and as=track fetches with a "track" Request.destination]
     expected: FAIL
 

testing/web-platform/meta/preload/preload-type-match.html.ini

@@ -57,12 +57,3 @@
   [Preload with {as=script; type=text/javascript1.1} should load when retrieved resource is a script]
     expected:
       if (processor == "x86") and (os == "win") and not debug: [PASS, FAIL]
-
-  [Preload with {as=json; type=application/json} should load when retrieved resource is a json]
-    expected: FAIL
-
-  [Preload with {as=json; type=text/json} should load when retrieved resource is a json]
-    expected: FAIL
-
-  [Preload with {as=json; type=application/geo+json} should load when retrieved resource is a json]
-    expected: FAIL