girepository: Make gi_repository_find_by_error_domain() deterministic

As with the previous commit, finding a `GIBaseInfo` matching the given
error domain was non-deterministic because it iterated through a hash
table of typelibs. Hash table iteration is non-deterministic.

Change the method to instead use the `ordered_typelibs` and
`ordered_lazy_typelibs` arrays to give deterministic iteration order.

Add a unit test, although it can’t test the interesting case of an error
domain which is present in both `GioUnix`/`GioWin32` and `Gio`, because
no such error domain exists.

Signed-off-by: Philip Withnall <pwithnall@gnome.org>

Helps: #3303

girepository/girepository.c

@@ -1078,28 +1078,27 @@ gi_repository_find_by_name (GIRepository *repository,
                            NULL, typelib, entry->offset);
 }
 
-typedef struct {
+static DirEntry *
-  GIRepository *repository;
+find_by_error_domain (GPtrArray  *ordered_typelibs,
-  GQuark domain;
+                      GQuark      target_domain,
-
+                      GITypelib **out_typelib)
-  GITypelib *result_typelib;
-  DirEntry *result;
-} FindByErrorDomainData;
-
-static void
-find_by_error_domain_foreach (gpointer key,
-                              gpointer value,
-                              gpointer datap)
 {
-  GITypelib *typelib = (GITypelib*)value;
+  /* Search in reverse order as the longest namespaces will be listed last, and
-  FindByErrorDomainData *data = datap;
+   * those are the ones we want to search first. */
+  for (guint i = ordered_typelibs->len; i > 0; i--)
+    {
+      GITypelib *typelib = g_ptr_array_index (ordered_typelibs, i - 1);
+      DirEntry *entry;
 
-  if (data->result != NULL)
+      entry = gi_typelib_get_dir_entry_by_error_domain (typelib, target_domain);
-    return;
+      if (entry != NULL)
+        {
+          *out_typelib = typelib;
+          return entry;
+        }
+    }
 
-  data->result = gi_typelib_get_dir_entry_by_error_domain (typelib, data->domain);
+  return NULL;
-  if (data->result)
-    data->result_typelib = typelib;
 }
 
 /**
@@ -1122,8 +1121,9 @@ GIEnumInfo *
 gi_repository_find_by_error_domain (GIRepository *repository,
                                     GQuark        domain)
 {
-  FindByErrorDomainData data;
   GIEnumInfo *cached;
+  DirEntry *result = NULL;
+  GITypelib *result_typelib = NULL;
 
   g_return_val_if_fail (GI_IS_REPOSITORY (repository), NULL);
 
@@ -1133,20 +1133,15 @@ gi_repository_find_by_error_domain (GIRepository *repository,
   if (cached != NULL)
     return (GIEnumInfo *) gi_base_info_ref ((GIBaseInfo *)cached);
 
-  data.repository = repository;
+  result = find_by_error_domain (repository->ordered_typelibs, domain, &result_typelib);
-  data.domain = domain;
+  if (result == NULL)
-  data.result_typelib = NULL;
+    result = find_by_error_domain (repository->ordered_lazy_typelibs, domain, &result_typelib);
-  data.result = NULL;
 
-  g_hash_table_foreach (repository->typelibs, find_by_error_domain_foreach, &data);
+  if (result != NULL)
-  if (data.result == NULL)
-    g_hash_table_foreach (repository->lazy_typelibs, find_by_error_domain_foreach, &data);
-
-  if (data.result != NULL)
     {
-      cached = (GIEnumInfo *) gi_info_new_full (gi_typelib_blob_type_to_info_type (data.result->blob_type),
+      cached = (GIEnumInfo *) gi_info_new_full (gi_typelib_blob_type_to_info_type (result->blob_type),
                                                 repository,
-                                                NULL, data.result_typelib, data.result->offset);
+                                                NULL, result_typelib, result->offset);
 
       g_hash_table_insert (repository->info_by_error_domain,
                            GUINT_TO_POINTER (domain),

girepository/tests/repository.c

@@ -513,12 +513,31 @@ test_repository_error_quark (RepositoryFixture *fx,
 
   g_test_summary ("Test finding an error quark by error domain");
 
+  /* Find a simple error domain. */
   error_info = gi_repository_find_by_error_domain (fx->repository, G_RESOLVER_ERROR);
   g_assert_nonnull (error_info);
   g_assert_true (GI_IS_ENUM_INFO (error_info));
   g_assert_cmpstr (gi_base_info_get_name (GI_BASE_INFO (error_info)), ==, "ResolverError");
 
   g_clear_pointer (&error_info, gi_base_info_unref);
+
+  /* Find again to check the caching. */
+  error_info = gi_repository_find_by_error_domain (fx->repository, G_RESOLVER_ERROR);
+  g_assert_nonnull (error_info);
+  g_assert_true (GI_IS_ENUM_INFO (error_info));
+  g_assert_cmpstr (gi_base_info_get_name (GI_BASE_INFO (error_info)), ==, "ResolverError");
+
+  g_clear_pointer (&error_info, gi_base_info_unref);
+
+  /* Try and find an unknown error domain. */
+  g_assert_null (gi_repository_find_by_error_domain (fx->repository, GI_REPOSITORY_ERROR));
+
+  /* And check caching for unknown error domains. */
+  g_assert_null (gi_repository_find_by_error_domain (fx->repository, GI_REPOSITORY_ERROR));
+
+  /* It would be good to try and find one which will resolve in both Gio and
+   * GioUnix/GioWin32, but neither of the platform-specific GIRs actually define
+   * any error domains at the moment. */
 }
 
 static void
@@ -861,7 +880,7 @@ main (int   argc,
   ADD_REPOSITORY_TEST ("/repository/constructor-return-type", test_repository_constructor_return_type, &typelib_load_spec_gobject);
   ADD_REPOSITORY_TEST ("/repository/enum-info-c-identifier", test_repository_enum_info_c_identifier, &typelib_load_spec_glib);
   ADD_REPOSITORY_TEST ("/repository/enum-info-static-methods", test_repository_enum_info_static_methods, &typelib_load_spec_glib);
-  ADD_REPOSITORY_TEST ("/repository/error-quark", test_repository_error_quark, &typelib_load_spec_gio);
+  ADD_REPOSITORY_TEST ("/repository/error-quark", test_repository_error_quark, &typelib_load_spec_gio_platform);
   ADD_REPOSITORY_TEST ("/repository/flags-info-c-identifier", test_repository_flags_info_c_identifier, &typelib_load_spec_gobject);
   ADD_REPOSITORY_TEST ("/repository/fundamental-ref-func", test_repository_fundamental_ref_func, &typelib_load_spec_gobject);
   ADD_REPOSITORY_TEST ("/repository/instance-method-ownership-transfer", test_repository_instance_method_ownership_transfer, &typelib_load_spec_gio);