Add tests for coro error/exception propogation.

Author: davits

test/embind/test_val_coro.cpp

@@ -16,10 +16,24 @@ EM_JS(EM_VAL, promise_sleep_impl, (int ms, int result), {
   return handle;
 });
 
+EM_JS(EM_VAL, promise_fail_impl, (), {
+  let promise = new Promise((_, reject) => setTimeout(reject, 1, new Error("bang from JS promise!")));
+  let handle = Emval.toHandle(promise);
+  // FIXME. See https://github.com/emscripten-core/emscripten/issues/16975.
+#if __wasm64__
+  handle = BigInt(handle);
+#endif
+  return handle;
+});
+
 val promise_sleep(int ms, int result = 0) {
   return val::take_ownership(promise_sleep_impl(ms, result));
 }
 
+val promise_fail() {
+  return val::take_ownership(promise_fail_impl());
+}
+
 // Test that we can subclass and make custom awaitable types.
 template <typename T>
 class typed_promise: public val {
@@ -37,7 +51,13 @@ class typed_promise: public val {
   }
 };
 
+template <size_t N>
 val asyncCoro() {
+  co_return co_await asyncCoro<N - 1>();
+}
+
+template <>
+val asyncCoro<0>() {
   // check that just sleeping works
   co_await promise_sleep(1);
   // check that sleeping and receiving value works
@@ -50,12 +70,48 @@ val asyncCoro() {
   co_return 34;
 }
 
+template <size_t N>
 val throwingCoro() {
+  co_await throwingCoro<N - 1>();
+  co_return 56;
+}
+
+template <>
+val throwingCoro<0>() {
   throw std::runtime_error("bang from throwingCoro!");
   co_return 56;
 }
 
+template <size_t N>
+val failingPromise() {
+  co_await failingPromise<N - 1>();
+  co_return 65;
+}
+
+template <>
+val failingPromise<0>() {
+  co_await promise_fail();
+  co_return 65;
+}
+
+val caughtException() {
+  int result = 0;
+  try {
+    co_return co_await throwingCoro<2>();
+  } catch (const val&) { // runtime_error turns into emscripten::val
+    result += 21;
+  }
+  try {
+    co_return co_await failingPromise<2>();
+  } catch (const val&) {
+    result += 21;
+  }
+  co_return result;
+}
+
 EMSCRIPTEN_BINDINGS(test_val_coro) {
-  function("asyncCoro", asyncCoro);
-  function("throwingCoro", throwingCoro);
+  function("asyncCoro", asyncCoro<3>);
+  function("throwingCoro", throwingCoro<3>);
+  function("failingPromise", failingPromise<3>);
+  function("caughtException", caughtException);
 }

test/test_core.py

@@ -7485,7 +7485,7 @@ def test_embind_val_coro(self):
     self.emcc_args += ['-std=c++20', '--bind', '--post-js=post.js']
     self.do_runf('embind/test_val_coro.cpp', '34\n')
 
-  def test_embind_val_coro_caught(self):
+  def test_embind_val_coro_propogate_cpp_exception(self):
     self.set_setting('EXCEPTION_STACK_TRACES')
     create_file('post.js', r'''Module.onRuntimeInitialized = () => {
       Module.throwingCoro().then(
@@ -7496,6 +7496,25 @@ def test_embind_val_coro_caught(self):
     self.emcc_args += ['-std=c++20', '--bind', '--post-js=post.js', '-fexceptions']
     self.do_runf('embind/test_val_coro.cpp', 'rejected with: std::runtime_error: bang from throwingCoro!\n')
 
+  def test_embind_val_coro_propogate_js_error(self):
+    self.set_setting('EXCEPTION_STACK_TRACES')
+    create_file('post.js', r'''Module.onRuntimeInitialized = () => {
+      Module.failingPromise().then(
+        console.log,
+        err => console.error(`rejected with: ${err.message}`)
+      );
+    }''')
+    self.emcc_args += ['-std=c++20', '--bind', '--post-js=post.js', '-fexceptions']
+    self.do_runf('embind/test_val_coro.cpp', 'rejected with: bang from JS promise!\n')
+
+  def test_embind_val_coro_caught_exception(self):
+    self.set_setting('EXCEPTION_STACK_TRACES')
+    create_file('post.js', r'''Module.onRuntimeInitialized = () => {
+      Module.caughtException().then(console.log);
+    }''')
+    self.emcc_args += ['-std=c++20', '--bind', '--post-js=post.js', '-fexceptions']
+    self.do_runf('embind/test_val_coro.cpp', '42\n')
+
   def test_embind_dynamic_initialization(self):
     self.emcc_args += ['-lembind']
     self.do_run_in_out_file_test('embind/test_dynamic_initialization.cpp')