[epiphany/mcatanzaro/web-app-crash] Broken web apps should crash in a nicer way

[Michael Catanzaro <mcatanzaro src gnome org>]

commit d513248ee94098ab85cf90959dda8343a26397e4
Author: Michael Catanzaro <mcatanzaro igalia com>
Date:   Tue Jun 18 16:15:03 2019 -0500

    Broken web apps should crash in a nicer way
    
    Although #713 is fixed for new users, anyone who previously suffered
    from a broken web app migration is doomed to eternal crashes. We
    probably can't reasonably recover the broken profile dir, but we should
    at least try to warn users what is going on.

 lib/ephy-settings.c | 36 +++++++++++++++++++++++++++++-------
 1 file changed, 29 insertions(+), 7 deletions(-)
---
diff --git a/lib/ephy-settings.c b/lib/ephy-settings.c
index 5ddd866e3..b5983f8c9 100644
--- a/lib/ephy-settings.c
+++ b/lib/ephy-settings.c
@@ -89,15 +89,37 @@ ephy_settings_get (const char *schema)
   ephy_settings_init ();
 
   gsettings = g_hash_table_lookup (settings, schema);
-
-  if (gsettings == NULL) {
-    gsettings = g_settings_new (schema);
-    if (gsettings == NULL)
-      g_warning ("Invalid schema %s requested", schema);
-    else
-      g_hash_table_insert (settings, g_strdup (schema), gsettings);
+  if (gsettings)
+    return gsettings;
+
+  if (strcmp (schema, EPHY_PREFS_WEB_APP_SCHEMA) == 0) {
+    /* EPHY_PREFS_WEB_APP_SCHEMA won't be added to the settings table if the
+     * ephy_profile_dir_is_web_application() is FALSE. But we can still get
+     * here in EPHY_EMBED_SHELL_MODE_APPLICATION if the profile dir is broken
+     * such that its .app file is missing. This includes any web apps created by
+     * Epiphany 3.30 or earlier that were migrated to 3.32 before 3.32.3 before
+     * the main profile migration. This generally means anybody using Epiphany
+     * only for web apps has wound up with broken web apps after the migration.
+     *
+     * We can only crash, but it's nicer to crash here rather than crash later.
+     *
+     * https://gitlab.gnome.org/GNOME/epiphany/issues/713
+     */
+    g_error ("Epiphany is trying to access web app settings outside web app"
+             " mode. Your web app may be broken. If so, you must delete it and"
+             " recreate. See epiphany#713.");
   }
 
+  /* schema must not be relocatable, or g_settings_new() will crash. */
+  for (guint i = 0; i < G_N_ELEMENTS (ephy_prefs_relocatable_schemas); i++)
+    g_assert (strcmp (schema, ephy_prefs_relocatable_schemas[i].schema) != 0);
+
+  gsettings = g_settings_new (schema);
+  if (gsettings == NULL)
+    g_warning ("Invalid schema %s requested", schema);
+  else
+    g_hash_table_insert (settings, g_strdup (schema), gsettings);
+
   return gsettings;
 }