Calling denoSub twice should fail.

3 files changed, 18 insertions, 0 deletions

diff --git a/deno2/deno.cc b/deno2/deno.cc
index 67b74bd63..26222d3b8 100644
--- a/deno2/deno.cc
+++ b/deno2/deno.cc
@@ -117,6 +117,11 @@ void Sub(const v8::FunctionCallbackInfo<v8::Value>& args) {
 
   v8::HandleScope handle_scope(isolate);
 
+  if (!d->sub.IsEmpty()) {
+    isolate->ThrowException(v8_str("denoSub already called."));
+    return;
+  }
+
   v8::Local<v8::Value> v = args[0];
   assert(v->IsFunction());
   v8::Local<v8::Function> func = v8::Local<v8::Function>::Cast(v);
diff --git a/deno2/js/mock_runtime.js b/deno2/js/mock_runtime.js
index 5702ed592..570d6cf28 100644
--- a/deno2/js/mock_runtime.js
+++ b/deno2/js/mock_runtime.js
@@ -49,3 +49,10 @@ function SubReturnBar() {
   const rstr = String.fromCharCode(...rui8);
   assert(rstr === "bar");
 }
+
+function DoubleSubFails() {
+  // denoSub is an internal function and should only be called once from the
+  // runtime.
+  denoSub((channel, msg) => assert(false));
+  denoSub((channel, msg) => assert(false));
+}
diff --git a/deno2/mock_runtime_test.cc b/deno2/mock_runtime_test.cc
index 44037044a..ea5ef4bf3 100644
--- a/deno2/mock_runtime_test.cc
+++ b/deno2/mock_runtime_test.cc
@@ -79,6 +79,12 @@ TEST(MockRuntimeTest, SubReturnBar) {
   deno_delete(d);
 }
 
+TEST(MockRuntimeTest, DoubleSubFails) {
+  Deno* d = deno_new(NULL, NULL);
+  EXPECT_FALSE(deno_execute(d, "a.js", "DoubleSubFails()"));
+  deno_delete(d);
+}
+
 int main(int argc, char** argv) {
   testing::InitGoogleTest(&argc, argv);
   deno_init();