fix shell extension updates

updates.d/80-gnome-extensions.sh

@@ -22,4 +22,40 @@ run_update() {
   else
     echo "gext update failed; GNOME extensions were not updated."
   fi
+
+  reinstall_incompatible_extensions
+}
+
+# gext only updates when the store's version number is higher than the installed
+# one, so a copy from elsewhere (e.g. a GitHub release with a different numbering)
+# can be stuck on a build that doesn't support the current GNOME Shell. GNOME
+# disables such extensions, so reinstall them fresh from extensions.gnome.org.
+reinstall_incompatible_extensions() {
+  local shell_major ext_root enabled dir uuid backup
+  shell_major="$(gnome-shell --version | grep -oE '[0-9]+' | head -1)"
+  ext_root="$HOME/.local/share/gnome-shell/extensions"
+  enabled="$(gsettings get org.gnome.shell enabled-extensions)"
+
+  for dir in "$ext_root"/*/; do
+    [ -f "$dir/metadata.json" ] || continue
+    uuid="$(basename "$dir")"
+    [[ "$enabled" == *"'$uuid'"* ]] || continue
+
+    if python3 -c 'import json, sys; m = json.load(open(sys.argv[1])); sys.exit(0 if any(str(v).split(".")[0] == sys.argv[2] for v in m.get("shell-version", [])) else 1)' \
+        "$dir/metadata.json" "$shell_major"; then
+      continue
+    fi
+
+    echo "$uuid doesn't support GNOME Shell $shell_major, reinstalling from extensions.gnome.org..."
+    backup="$(mktemp -d)"
+    mv "$dir" "$backup/$uuid"
+    if ~/.local/bin/gext --filesystem install "$uuid" && [ -f "$ext_root/$uuid/metadata.json" ]; then
+      rm -rf "$backup"
+    else
+      echo "Reinstall of $uuid failed; restoring the previous version."
+      rm -rf "$ext_root/$uuid"
+      mv "$backup/$uuid" "$ext_root/$uuid"
+      rmdir "$backup"
+    fi
+  done
 }