index.ts

type PermissionChangeCallback = (callback: chrome.permissions.Permissions) => void;

const events = [
	['request', 'onAdded'],
	['remove', 'onRemoved']
] as const;

if (chrome.permissions && !chrome.permissions.onAdded) {
	for (const [action, event] of events) {
		const act = chrome.permissions[action];
		const listeners = new Set<PermissionChangeCallback>();

		// Collect
		chrome.permissions[event] = {
			addListener(callback) {
				listeners.add(callback);
			}
		};

		// Listen into requests and fire callbacks
		chrome.permissions[action] = (permissions, callback) => {
			const initial = browser.permissions.contains(permissions);
			const expected = action === 'request';
			act(permissions, async successful => {
				if (callback) {
					callback(successful);
				}

				if (!successful) {
					return;
				}

				// Only fire events if they changed
				if (await initial !== expected) {
					const fullPermissions = {origins: [], permissions: [], ...permissions};

					// Firefox won't run asynchronous functions without this
					chrome.permissions.getAll(() => {
						for (const listener of listeners) {
							setTimeout(listener, 0, fullPermissions); // Run all listeners even if one errors
						}
					});

					// Enable polyfill to work across contexts
					chrome.runtime.sendMessage({
						permissionsEventsPolyfill: permissions
					});
				}
			});
		};

		// @ts-ignore `onAdded` is specified as `const`, but isn't
		browser.permissions[event] = chrome.permissions[event];
		// TODO: drop `as 'request'` after https://github.com/jsmnbom/definitelytyped-firefox-webext-browser/issues/22
		browser.permissions[action as 'request'] = async (permissions: chrome.permissions.Permissions) => new Promise<boolean>((resolve, reject) => {
			chrome.permissions[action](permissions, result => {
				if (chrome.runtime.lastError) {
					reject(chrome.runtime.lastError);
				} else {
					resolve(result);
				}
			});
		});

		// Enable polyfill to work across contexts
		if (chrome.runtime.onMessage) {
			chrome.runtime.onMessage.addListener(message => {
				if (message && message.permissionsEventsPolyfill) {
					for (const listener of listeners) {
						setTimeout(listener, 0, message.permissionsEventsPolyfill);
					}
				}
			});
		}
	}
}