fix: don't exit on reload if there is a syntax error (#213)

Author: David Laban

src/functions_framework/__init__.py

@@ -350,11 +350,27 @@ def handle_none(rv):
 
     # Execute the module, within the application context
     with _app.app_context():
-        spec.loader.exec_module(source_module)
+        try:
+            spec.loader.exec_module(source_module)
+            function = _function_registry.get_user_function(source, source_module, target)
+        except Exception as e:
+            if werkzeug.serving.is_running_from_reloader():
+                # When reloading, print out the error immediately, but raise
+                # it later so the debugger or server can handle it.
+                import traceback
+                traceback.print_exc()
+                err = e
+
+                def function(*_args, **_kwargs):
+                    raise err from None
+
+            else:
+                # When not reloading, raise the error immediately so the
+                # command fails.
+                raise e from None
 
     # Get the configured function signature type
     signature_type = _function_registry.get_func_signature_type(target, signature_type)
-    function = _function_registry.get_user_function(source, source_module, target)
 
     _configure_app(_app, function, signature_type)