girepository: Return enumerated versions as a GStrv

Returning list of strings is a bad idea, so let's do not now since
we're exposing the API for the first time.

girepository/girepository.c

@@ -1558,28 +1558,39 @@ find_namespace_latest (const gchar  *namespace,
  * @repository: (nullable): A #GIRepository, or `NULL` for the singleton
  *   process-global default #GIRepository
  * @namespace_: GI namespace, e.g. `Gtk`
+ * @n_versions_out: (optional) (out): The number of versions returned.
  *
  * Obtain an unordered list of versions (either currently loaded or
  * available) for @namespace_ in this @repository.
  *
- * Returns: (element-type utf8) (transfer full): the array of versions.
+ * Returns: (element-type utf8) (transfer full) (array length=n_versions_out): the array of versions.
  * Since: 2.80
  */
-GList *
+char **
 gi_repository_enumerate_versions (GIRepository *repository,
-                                  const gchar  *namespace_)
+                                  const gchar  *namespace_,
+                                  size_t       *n_versions_out)
 {
-  GList *ret = NULL;
+  GPtrArray *versions;
   GSList *candidates, *link;
   const gchar *loaded_version;
+  char **ret;
 
   init_globals ();
   candidates = enumerate_namespace_versions (namespace_, typelib_search_path);
 
+  if (!candidates)
+    {
+      if (n_versions_out)
+        *n_versions_out = 0;
+      return g_strdupv ((char *[]) {NULL});
+    }
+
+  versions = g_ptr_array_new_null_terminated (1, g_free, TRUE);
   for (link = candidates; link; link = link->next)
     {
       struct NamespaceVersionCandidadate *candidate = link->data;
-      ret = g_list_prepend (ret, g_strdup (candidate->version));
+      g_ptr_array_add (versions, g_steal_pointer (&candidate->version));
       free_candidate (candidate);
     }
   g_slist_free (candidates);
@@ -1591,10 +1602,14 @@ gi_repository_enumerate_versions (GIRepository *repository,
   if (gi_repository_is_registered (repository, namespace_, NULL))
     {
       loaded_version = gi_repository_get_version (repository, namespace_);
-      if (loaded_version && !g_list_find_custom (ret, loaded_version, g_str_equal))
+      if (loaded_version &&
-        ret = g_list_prepend (ret, g_strdup (loaded_version));
+          !g_ptr_array_find_with_equal_func (versions, loaded_version, g_str_equal, NULL))
+        g_ptr_array_add (versions, g_strdup (loaded_version));
     }
 
+  ret = (char **) g_ptr_array_steal (versions, n_versions_out);
+  g_ptr_array_unref (g_steal_pointer (&versions));
+
   return ret;
 }
 

girepository/girepository.h

@@ -128,8 +128,9 @@ GIBaseInfo *  gi_repository_find_by_name  (GIRepository *repository,
                                            const gchar  *name);
 
 GI_AVAILABLE_IN_ALL
-GList *       gi_repository_enumerate_versions (GIRepository *repository,
+char       ** gi_repository_enumerate_versions (GIRepository *repository,
-                                                const gchar  *namespace_);
+                                                const gchar  *namespace_,
+                                                size_t       *n_versions_out);
 
 GI_AVAILABLE_IN_ALL
 GITypelib *    gi_repository_require       (GIRepository           *repository,

girepository/tests/repository.c

@@ -32,6 +32,8 @@ test_repository_basic (void)
   char **namespaces = NULL;
   const char *expected_namespaces[] = { "GLib", NULL };
   GError *local_error = NULL;
+  char **versions;
+  size_t n_versions;
 
   g_test_summary ("Test basic opening of a repository and requiring a typelib");
 
@@ -42,6 +44,17 @@ test_repository_basic (void)
   repository = gi_repository_new ();
   g_assert_nonnull (repository);
 
+  versions = gi_repository_enumerate_versions (repository, "SomeInvalidNamespace", &n_versions);
+  g_assert_nonnull (versions);
+  g_assert_cmpstrv (versions, ((char *[]){NULL}));
+  g_assert_cmpuint (n_versions, ==, 0);
+  g_clear_pointer (&versions, g_strfreev);
+
+  versions = gi_repository_enumerate_versions (repository, "GLib", NULL);
+  g_assert_nonnull (versions);
+  g_assert_cmpstrv (versions, ((char *[]){"2.0", NULL}));
+  g_clear_pointer (&versions, g_strfreev);
+
   search_path = gi_repository_get_search_path ();
   g_assert_nonnull (search_path);
   g_assert_cmpstr (search_path->data, ==, gobject_typelib_dir);