Protect exportFunction with defineAs

For #429

lib/extension.js

@@ -13,6 +13,7 @@
 	}
 	
 	const browserAvailable = typeof browser !== "undefined";
+	const logging = require("./logging");
 	
 	scope.inBackgroundScript = !!(
 		browserAvailable &&
@@ -60,6 +61,13 @@
 				defineAs: name
 			};
 			const oldDescriptor = Object.getOwnPropertyDescriptor(wrappedContext, name);
+			if (oldDescriptor && !oldDescriptor.configurable){
+				logging.error(
+					"Unable to export function with the correct name", name,
+					"instead we have to use", exportedTry.name
+				);
+				return exportedTry;
+			}
 			const exported = exportFunction(func, context, options);
 			if (oldDescriptor){
 				Object.defineProperty(wrappedContext, name, oldDescriptor);

versions/updates.json

@@ -101,6 +101,10 @@
 				{
 					"version": "1.1Alpha20191801",
 					"update_link": "https://canvasblocker.kkapsner.de/versions/canvasblocker_beta-1.1Alpha20191801-an+fx.xpi"
+				},
+				{
+					"version": "1.1Alpha20191901",
+					"update_link": "https://canvasblocker.kkapsner.de/versions/canvasblocker_beta-1.1Alpha20191901-an+fx.xpi"
 				}
 			]
 		}