fix(core): provide mock implementation for unimplemented platforms (#…

…3352)

core/src/plugins.ts

@@ -50,11 +50,38 @@ export class RegisteredPlugin<T> {
    * method will return the implementation for the current platform as detected
    * by Capacitor.
    *
+   * If an implementation for the specified platform does not exist, a mock
+   * implementation is returned which throws 'unimplemented' errors for every
+   * method call and property access.
+   *
    * @param platform Optionally return the implementation of the given
    *                 platform.
    */
-  getImplementation(platform?: string): T | undefined {
-    return this.implementations[platform ? platform : Capacitor.platform];
+  getImplementation(platform: string = Capacitor.platform): T {
+    const implementation = this.implementations[platform];
+
+    if (!implementation) {
+      // Degraded experience for non-Proxy environments, e.g. IE11.
+      if (typeof Proxy === 'undefined') {
+        return;
+      }
+
+      return new Proxy({}, this.createImplementationProxyHandler(platform));
+    }
+
+    return implementation;
+  }
+
+  protected createImplementationProxyHandler(
+    platform: string,
+  ): ProxyHandler<any> {
+    return {
+      get: () => {
+        throw new Error(
+          `${this.name} does not have an implementation for ${platform}.`,
+        );
+      },
+    };
   }
 }