LibWeb: Fix race condition between read_all_bytes and stream population

There might be a race between read_all_bytes and stream population.
If document load reads stream before it is populated, the stream will
be empty and might lead to hang in SessionHistoryTraversalQueue which
is expecting a promise to be resolved on document load.

This race can occur when stream population and document source are set
very close to each other. For example, when a newly generated blob is
set as the source of an iframe.
- navigation/multiple-navigable-cross-document-navigation.html has been
modified to trigger this race.

Author: prajjwal000

Libraries/LibWeb/Fetch/BodyInit.cpp

@@ -145,24 +145,24 @@ WebIDL::ExceptionOr<Infrastructure::BodyWithType> extract_body(JS::Realm& realm,
 
     // 12. If action is non-null, then run these steps in parallel:
     if (action) {
-        Platform::EventLoopPlugin::the().deferred_invoke(GC::create_function(realm.heap(), [&realm, stream, action = move(action)] {
-            HTML::TemporaryExecutionContext execution_context { realm, HTML::TemporaryExecutionContext::CallbacksEnabled::Yes };
+        // AD-HOC: There is a race condition between document population(Ex: load_html_document->fully_read->read_all_bytes->readable_stream_default_reader_read)
+        // and stream population. So currently we run stream population synchronously.
+        HTML::TemporaryExecutionContext execution_context { realm, HTML::TemporaryExecutionContext::CallbacksEnabled::Yes };
 
-            // 1. Run action.
-            auto bytes = action();
+        // 1. Run action.
+        auto bytes = action();
 
-            // Whenever one or more bytes are available and stream is not errored, enqueue the result of creating a
-            // Uint8Array from the available bytes into stream.
-            if (!bytes.is_empty() && !stream->is_errored()) {
-                auto array_buffer = JS::ArrayBuffer::create(stream->realm(), move(bytes));
-                auto chunk = JS::Uint8Array::create(stream->realm(), array_buffer->byte_length(), *array_buffer);
+        // Whenever one or more bytes are available and stream is not errored, enqueue the result of creating a
+        // Uint8Array from the available bytes into stream.
+        if (!bytes.is_empty() && !stream->is_errored()) {
+            auto array_buffer = JS::ArrayBuffer::create(stream->realm(), move(bytes));
+            auto chunk = JS::Uint8Array::create(stream->realm(), array_buffer->byte_length(), *array_buffer);
 
-                stream->enqueue(chunk).release_value_but_fixme_should_propagate_errors();
-            }
+            stream->enqueue(chunk).release_value_but_fixme_should_propagate_errors();
+        }
 
-            // When running action is done, close stream.
-            stream->close();
-        }));
+        // When running action is done, close stream.
+        stream->close();
     }
 
     // 13. Let body be a body whose stream is stream, source is source, and length is length.

Tests/LibWeb/Text/expected/navigation/multiple-navigable-cross-document-navigation.txt

@@ -1,2 +1,4 @@
 PASS
 PASS
+PASS
+PASS

Tests/LibWeb/Text/input/navigation/multiple-navigable-cross-document-navigation.html

@@ -2,10 +2,12 @@
 <script src="../include.js"></script>
 <iframe id="a"></iframe>
 <iframe id="b"></iframe>
+<iframe id="c"></iframe>
+<iframe id="d"></iframe>
 <script>
     asyncTest(done => {
-        let doneA = false, doneB = false;
-        function check() {if (doneA && doneB) done();}
+        let doneA = false, doneB = false, doneC = false, doneD = false;
+        function check() {if (doneA && doneB && doneC && doneD) done();}
         function makeContent(id, n) {
             let html = `<h3>${id} ${n}</h3>`;
             if (n % 3 === 0) html += `<iframe id="nest1+${id}" srcdoc="${id} ${n}"></iframe>`;
@@ -27,5 +29,7 @@
         }
         run(document.getElementById('a'), 'a', 0, 101, () => {doneA = true; check();});
         run(document.getElementById('b'), 'b', 0, 101, () => {doneB = true; check();});
+        run(document.getElementById('c'), 'c', 0, 101, () => {doneC = true; check();});
+        run(document.getElementById('d'), 'd', 0, 101, () => {doneD = true; check();});
     });
 </script>