Remove 'Implicit Async', Don't Await runtime.run() (#928)

* Revert to runPython instead of await runPythonAsync

* "Implicit Coroutines" are no longer permitted in py-script tags

* Tests added for the above

* xfail test_importmap (See #938)

pyscriptjs/src/python/pyscript.py

@@ -1,3 +1,4 @@
+import ast
 import asyncio
 import base64
 import html
@@ -404,4 +405,28 @@ class PyListTemplate:
         pass
 
 
+class TopLevelAsyncFinder(ast.NodeVisitor):
+    def is_source_top_level_await(self, source):
+        self.async_found = False
+        node = ast.parse(source)
+        self.generic_visit(node)
+        return self.async_found
+
+    def visit_Await(self, node):
+        self.async_found = True
+
+    def visit_AsyncFor(self, node):
+        self.async_found = True
+
+    def visit_AsyncWith(self, node):
+        self.async_found = True
+
+    def visit_AsyncFunctionDef(self, node: ast.AsyncFunctionDef):
+        pass  # Do not visit children of async function defs
+
+
+def uses_top_level_await(source: str) -> bool:
+    return TopLevelAsyncFinder().is_source_top_level_await(source)
+
+
 pyscript = PyScript()