| def main(request, response): | |
| # Set mode to 'init' for initial fetch. | |
| mode = 'init' | |
| if 'update-recovery-mode' in request.cookies: | |
| mode = request.cookies['update-recovery-mode'].value | |
| # no-cache itself to ensure the user agent finds a new version for each update. | |
| headers = [('Cache-Control', 'no-cache, must-revalidate'), | |
| ('Pragma', 'no-cache')] | |
| extra_body = '' | |
| if mode == 'init': | |
| # Install a bad service worker that will break the controlled | |
| # document navigation. | |
| response.set_cookie('update-recovery-mode', 'bad') | |
| extra_body = "addEventListener('fetch', function(e) { e.respondWith(Promise.reject()); });" | |
| elif mode == 'bad': | |
| # When the update tries to pull the script again, update to | |
| # a worker service worker that does not break document | |
| # navigation. Serve the same script from then on. | |
| response.delete_cookie('update-recovery-mode') | |
| headers.append(('Content-Type', 'application/javascript')) | |
| return headers, '%s' % (extra_body) |