[wasm] Fix streaming instantiation with no code section

Because of ordering issues we didn't set the wire bytes on the
{NativeModule} during {OnFinishedStream}. We then failed during
instantiation when trying to read the import names from the wire bytes.

This CL fixes this locally without much code churn. I plan to clean up
the interaction between {AsyncCompileJob} and {AsyncStreamingProcessor}
in a follow-up CL.

R=ahaas@chromium.org

Bug: chromium:898310
Change-Id: I06337a04ba380f87b803f325323208298d363f41
Reviewed-on: https://chromium-review.googlesource.com/c/1296467Reviewed-by: Andreas Haas <ahaas@chromium.org>
Commit-Queue: Clemens Hammacher <clemensh@chromium.org>
Cr-Commit-Position: refs/heads/master@{#56938}

src/wasm/module-compiler.cc

@@ -2365,12 +2365,6 @@ void AsyncCompileJob::CancelPendingForegroundTask() {
   pending_foreground_task_ = nullptr;
 }
 
-template <typename Step, typename... Args>
-void AsyncCompileJob::DoSync(Args&&... args) {
-  NextStep<Step>(std::forward<Args>(args)...);
-  StartForegroundTask();
-}
-
 void AsyncCompileJob::StartBackgroundTask() {
   auto task = base::make_unique<CompileTask>(this, false);
 
@@ -2383,6 +2377,18 @@ void AsyncCompileJob::StartBackgroundTask() {
   }
 }
 
+template <typename Step, typename... Args>
+void AsyncCompileJob::DoSync(Args&&... args) {
+  NextStep<Step>(std::forward<Args>(args)...);
+  StartForegroundTask();
+}
+
+template <typename Step, typename... Args>
+void AsyncCompileJob::DoImmediately(Args&&... args) {
+  NextStep<Step>(std::forward<Args>(args)...);
+  ExecuteForegroundTaskImmediately();
+}
+
 template <typename Step, typename... Args>
 void AsyncCompileJob::DoAsync(Args&&... args) {
   NextStep<Step>(std::forward<Args>(args)...);
@@ -2726,11 +2732,10 @@ bool AsyncStreamingProcessor::ProcessCodeSectionHeader(size_t functions_count,
     FinishAsyncCompileJobWithError(decoder_.FinishDecoding(false));
     return false;
   }
-  job_->NextStep<AsyncCompileJob::PrepareAndStartCompile>(
-      decoder_.shared_module(), false);
   // Execute the PrepareAndStartCompile step immediately and not in a separate
   // task.
-  job_->ExecuteForegroundTaskImmediately();
+  job_->DoImmediately<AsyncCompileJob::PrepareAndStartCompile>(
+      decoder_.shared_module(), false);
 
   job_->native_module_->compilation_state()->SetNumberOfFunctionsToCompile(
       functions_count);
@@ -2773,26 +2778,26 @@ void AsyncStreamingProcessor::OnFinishedChunk() {
 // Finish the processing of the stream.
 void AsyncStreamingProcessor::OnFinishedStream(OwnedVector<uint8_t> bytes) {
   TRACE_STREAMING("Finish stream...\n");
-  if (job_->native_module_) {
-    job_->wire_bytes_ = ModuleWireBytes(bytes.as_vector());
-    job_->native_module_->set_wire_bytes(std::move(bytes));
-  }
   ModuleResult result = decoder_.FinishDecoding(false);
   DCHECK(result.ok());
-  if (job_->DecrementAndCheckFinisherCount()) {
-    if (job_->native_module_ == nullptr) {
-      // We are processing a WebAssembly module without code section. We need to
-      // prepare compilation first before we can finish it.
-      // {PrepareAndStartCompile} will call {FinishCompile} by itself if there
-      // is no code section.
-      job_->DoSync<AsyncCompileJob::PrepareAndStartCompile>(
-          std::move(result).value(), true);
-    } else {
-      HandleScope scope(job_->isolate_);
-      SaveContext saved_context(job_->isolate_);
-      job_->isolate_->set_context(*job_->native_context_);
-      job_->FinishCompile(true);
-    }
+  bool needs_finish = job_->DecrementAndCheckFinisherCount();
+  if (job_->native_module_ == nullptr) {
+    // We are processing a WebAssembly module without code section. We need to
+    // prepare compilation first before we can finish it.
+    // {PrepareAndStartCompile} will call {FinishCompile} by itself if there
+    // is no code section.
+    DCHECK(needs_finish);
+    needs_finish = false;
+    job_->DoImmediately<AsyncCompileJob::PrepareAndStartCompile>(
+        std::move(result).value(), true);
+  }
+  job_->wire_bytes_ = ModuleWireBytes(bytes.as_vector());
+  job_->native_module_->set_wire_bytes(std::move(bytes));
+  if (needs_finish) {
+    HandleScope scope(job_->isolate_);
+    SaveContext saved_context(job_->isolate_);
+    job_->isolate_->set_context(*job_->native_context_);
+    job_->FinishCompile(true);
   }
 }
 

src/wasm/module-compiler.h

@@ -116,6 +116,10 @@ class AsyncCompileJob {
   template <typename Step, typename... Args>
   void DoSync(Args&&... args);
 
+  // Switches to the compilation step {Step} and immediately executes that step.
+  template <typename Step, typename... Args>
+  void DoImmediately(Args&&... args);
+
   // Switches to the compilation step {Step} and starts a background task to
   // execute it.
   template <typename Step, typename... Args>

test/mjsunit/wasm/async-compile.js

@@ -70,3 +70,10 @@ assertPromiseResult(async function badFunctionInTheMiddle() {
   let buffer = builder.toBuffer();
   await assertCompileError(buffer);
 }());
+
+assertPromiseResult(async function importWithoutCode() {
+  // Regression test for https://crbug.com/898310.
+  let builder = new WasmModuleBuilder();
+  builder.addImport('m', 'q', kSig_i_i);
+  await builder.asyncInstantiate({'m': {'q': i => i}});
+}());