webassembly/asyncio: Fix case where a Promise is resolved with no arg.

Signed-off-by: Damien George <damien@micropython.org>

ports/webassembly/asyncio/core.py

@@ -75,7 +75,7 @@ class ThenableEvent:
         self.waiting = None  # Task waiting on completion of this thenable
         thenable.then(self.set)
 
-    def set(self, value):
+    def set(self, value=None):
         # Thenable/Promise is fulfilled, set result and schedule any waiting task.
         self.result = value
         if self.waiting:

tests/ports/webassembly/asyncio_await_resolve_no_arg.mjs

@@ -0,0 +1,21 @@
+// Test an asyncio task await'ing on a Promise that's resolved without an argument.
+
+const mp = await (await import(process.argv[2])).loadMicroPython();
+
+globalThis.foo = new Promise((resolve) => {
+    console.log(1);
+    resolve(); // resolve without an argument
+    console.log(2);
+});
+
+mp.runPython(`
+import asyncio
+import js
+
+async def task():
+    print(3)
+    print(await js.foo)
+    print(4)
+
+asyncio.create_task(task())
+`);

tests/ports/webassembly/asyncio_await_resolve_no_arg.mjs.exp

@@ -0,0 +1,5 @@
+1
+2
+3
+None
+4