Delete Service Worker directory on Qt upgrades

QtWebEngine upgrades seem to have issues with old service workers around. As a
workaround, let's delete the Service Worker directory (keeping one backup
around) when the Qt version changes (and also once on Qt 5.14 to get rid of
existing bad data).

Related Qt issues:

- https://bugreports.qt.io/browse/QTBUG-72532
- https://bugreports.qt.io/browse/QTBUG-82105

It seems to be okay to delete those, as the website can re-register them, and
they don't seem to have any persistent data storage. Relevant reading:

- https://github.com/chromium/chromium/blob/master/content/browser/service_worker/README.md
- https://developer.mozilla.org/en-US/docs/Web/API/Service_Worker_API
- https://w3c.github.io/ServiceWorker/
- https://developer.mozilla.org/en-US/docs/Web/API/CacheStorage

Fixes #4853

(cherry picked from commit 84541de04b06f3d40d11fb38669367b0905f04a0)

1 files changed, 36 insertions, 0 deletions

diff --git a/qutebrowser/misc/backendproblem.py b/qutebrowser/misc/backendproblem.py
index dd99de378..6aab87ea6 100644
--- a/qutebrowser/misc/backendproblem.py
+++ b/qutebrowser/misc/backendproblem.py
@@ -440,6 +440,41 @@ class _BackendProblemChecker:
         if os.path.exists(cache_dir):
             shutil.rmtree(cache_dir)
 
+    def _handle_serviceworker_nuking(self) -> None:
+        """Nuke the service workers directory if the Qt version changed.
+
+        WORKAROUND for:
+        https://bugreports.qt.io/browse/QTBUG-72532
+        https://bugreports.qt.io/browse/QTBUG-82105
+        """
+        if ('serviceworker_workaround' not in configfiles.state['general'] and
+                qtutils.version_check('5.14', compiled=False)):
+            # Nuke the service worker directory once for every install with Qt
+            # 5.14, given that it seems to cause a variety of segfaults.
+            configfiles.state['general']['serviceworker_workaround'] = '514'
+            affected = True
+        else:
+            # Otherwise, just nuke it when the Qt version changed.
+            affected = configfiles.state.qt_version_changed
+
+        if not affected:
+            return
+
+        service_worker_dir = os.path.join(standarddir.data(), 'webengine',
+                                          'Service Worker')
+        bak_dir = service_worker_dir + '-bak'
+        if not os.path.exists(service_worker_dir):
+            return
+
+        log.init.info("Qt version changed, removing service workers")
+
+        # Keep one backup around - we're not 100% sure what persistent data
+        # could be in there, but this folder can grow to ~300 MB.
+        if os.path.exists(bak_dir):
+            shutil.rmtree(bak_dir)
+
+        shutil.move(service_worker_dir, bak_dir)
+
     def _assert_backend(self, backend: usertypes.Backend) -> None:
         assert objects.backend == backend, objects.backend
 
@@ -452,6 +487,7 @@ class _BackendProblemChecker:
             self._nvidia_shader_workaround()
             self._handle_nouveau_graphics()
             self._handle_cache_nuking()
+            self._handle_serviceworker_nuking()
         else:
             self._assert_backend(usertypes.Backend.QtWebKit)
             self._handle_ssl_support(fatal=True)