Adding rollup-plugin-google-apps-script.

README.md

@@ -118,6 +118,24 @@ import './path/to/module';
 
 This will ensure that Rollup will not remove it from the bundle.
 
+### Linter not allowing unused variables
+
+A [plugin for Google App Script](https://github.com/mato533/rollup-plugin-gas) is included in the Rollup configuration. This automatically creates top-level functions for anything declared on the global object. To avoid unused variables in your code, first use `declare global` to declare the functions you need, and then assign the actual function to your declaration. e.g.:
+
+```ts
+declare global {
+  onOpen(): void;
+}
+
+function onOpenFunc(): void {
+  SpreadsheetApp.getUI().createMenu('Stuff').addToUI();
+}
+
+global.onOpen = onOpenFunc;
+```
+
+This would result in a top-level `onOpen` function being created in the build results.
+
 ## Disclaimer
 
 This is not an officially supported Google product.

package.json

@@ -70,6 +70,7 @@
     "prettier": "^2.8.5",
     "rimraf": "^4.4.0",
     "rollup": "^3.20.0",
+    "rollup-plugin-google-apps-script": "^2.0.2",
     "ts-jest": "^29.0.5",
     "tslib": "^2.5.0",
     "typescript": "^4.9.5"

rollup.config.mjs

@@ -16,6 +16,7 @@
 import cleanup from 'rollup-plugin-cleanup';
 import license from 'rollup-plugin-license';
 import prettier from 'rollup-plugin-prettier';
+import rollupPluginGas from 'rollup-plugin-google-apps-script';
 import typescript from 'rollup-plugin-typescript2';
 import { fileURLToPath } from 'url';
 
@@ -36,6 +37,7 @@ export default {
     }),
     typescript(),
     prettier({ parser: 'typescript' }),
+    rollupPluginGas(),
   ],
   context: 'this',
 };