lib-storage: Add mailbox_list_last_error_push/pop()

These are similar to mail_storage_last_error_push/pop()

src/lib-storage/mailbox-list-private.h

@@ -134,6 +134,7 @@ struct mailbox_list {
 	char *error_string;
 	enum mail_error error;
 	bool temporary_error;
+	ARRAY(struct mail_storage_error) error_stack;
 
 	ARRAY(union mailbox_list_module_context *) module_contexts;
 

src/lib-storage/mailbox-list.c

@@ -791,6 +791,11 @@ void mailbox_list_destroy(struct mailbox_list **_list)
 		mailbox_tree_deinit(&list->subscriptions);
 	if (list->changelog != NULL)
 		mailbox_log_free(&list->changelog);
+
+	if (array_is_created(&list->error_stack)) {
+		i_assert(array_count(&list->error_stack) == 0);
+		array_free(&list->error_stack);
+	}
 	list->v.deinit(list);
 }
 
@@ -1907,6 +1912,35 @@ bool mailbox_list_set_error_from_errno(struct mailbox_list *list)
 	return TRUE;
 }
 
+void mailbox_list_last_error_push(struct mailbox_list *list)
+{
+	struct mail_storage_error *err;
+
+	if (!array_is_created(&list->error_stack))
+		i_array_init(&list->error_stack, 2);
+	err = array_append_space(&list->error_stack);
+	err->error_string = i_strdup(list->error_string);
+	err->error = list->error;
+	err->last_error_is_internal = list->last_error_is_internal;
+	if (err->last_error_is_internal)
+		err->last_internal_error = i_strdup(list->last_internal_error);
+}
+
+void mailbox_list_last_error_pop(struct mailbox_list *list)
+{
+	unsigned int count = array_count(&list->error_stack);
+	const struct mail_storage_error *err =
+		array_idx(&list->error_stack, count-1);
+
+	i_free(list->error_string);
+	i_free(list->last_internal_error);
+	list->error_string = err->error_string;
+	list->error = err->error;
+	list->last_error_is_internal = err->last_error_is_internal;
+	list->last_internal_error = err->last_internal_error;
+	array_delete(&list->error_stack, count-1, 1);
+}
+
 int mailbox_list_init_fs(struct mailbox_list *list, const char *driver,
 			 const char *args, const char *root_dir,
 			 struct fs **fs_r, const char **error_r)

src/lib-storage/mailbox-list.h

@@ -278,6 +278,12 @@ const char * ATTR_NOWARN_UNUSED_RESULT
 mailbox_list_get_last_internal_error(struct mailbox_list *list,
 				     enum mail_error *error_r);
 
+/* Save the last error until it's popped. This is useful for cases where the
+   list operation has already failed, but the cleanup code path changes the
+   error to something else unwanted. */
+void mailbox_list_last_error_push(struct mailbox_list *list);
+void mailbox_list_last_error_pop(struct mailbox_list *list);
+
 /* Create a fs based on the settings in the given mailbox_list. */
 int mailbox_list_init_fs(struct mailbox_list *list, const char *driver,
 			 const char *args, const char *root_dir,