lib-storage: Add mail_storage_get_last_internal_error()

This returns the error given to mail_storage_set_critical().

src/lib-storage/mail-storage-private.h

@@ -128,6 +128,9 @@ struct mail_storage {
 	 * uniqueness checking (via strcmp) and never used as a path. */
 	const char *unique_root_dir;
 
+	/* Last error set in mail_storage_set_critical(). */
+	char *last_internal_error;
+
 	char *error_string;
 	enum mail_error error;
 	ARRAY(struct mail_storage_error) error_stack;
@@ -152,6 +155,7 @@ struct mail_storage {
 
 	/* Failed to create shared attribute dict, don't try again */
 	unsigned int shared_attr_dict_failed:1;
+	unsigned int last_error_is_internal:1;
 };
 
 struct mail_attachment_part {

src/lib-storage/mail-storage.c

@@ -452,6 +452,7 @@ void mail_storage_unref(struct mail_storage **_storage)
 	DLLIST_REMOVE(&storage->user->storages, storage);
 
 	storage->v.destroy(storage);
+	i_free(storage->last_internal_error);
 	i_free(storage->error_string);
 	if (array_is_created(&storage->error_stack)) {
 		i_assert(array_count(&storage->error_stack) == 0);
@@ -487,6 +488,8 @@ void mail_storage_clear_error(struct mail_storage *storage)
 {
 	i_free_and_null(storage->error_string);
 
+	i_free(storage->last_internal_error);
+	storage->last_error_is_internal = FALSE;
 	storage->error = MAIL_ERROR_NONE;
 }
 
@@ -497,6 +500,7 @@ void mail_storage_set_error(struct mail_storage *storage,
 		i_free(storage->error_string);
 		storage->error_string = i_strdup(string);
 	}
+	storage->last_error_is_internal = FALSE;
 	storage->error = error;
 }
 
@@ -516,16 +520,38 @@ void mail_storage_set_critical(struct mail_storage *storage,
 {
 	va_list va;
 
+	i_free(storage->last_internal_error);
 	va_start(va, fmt);
-	i_error("%s", t_strdup_vprintf(fmt, va));
+	storage->last_internal_error = i_strdup_vprintf(fmt, va);
 	va_end(va);
+	storage->last_error_is_internal = TRUE;
+	i_error("%s", storage->last_internal_error);
 
 	/* critical errors may contain sensitive data, so let user
 	   see only "Internal error" with a timestamp to make it
 	   easier to look from log files the actual error message. */
 	mail_storage_set_internal_error(storage);
 }
 
+const char *mail_storage_get_last_internal_error(struct mail_storage *storage,
+						 enum mail_error *error_r)
+{
+	if (error_r != NULL)
+		*error_r = storage->error;
+	if (storage->last_error_is_internal) {
+		i_assert(storage->last_internal_error != NULL);
+		return storage->last_internal_error;
+	}
+	return mail_storage_get_last_error(storage, error_r);
+}
+
+const char *mailbox_get_last_internal_error(struct mailbox *box,
+					    enum mail_error *error_r)
+{
+	return mail_storage_get_last_internal_error(mailbox_get_storage(box),
+						    error_r);
+}
+
 void mail_storage_copy_error(struct mail_storage *dest,
 			     struct mail_storage *src)
 {

src/lib-storage/mail-storage.h

@@ -481,6 +481,14 @@ mailbox_get_last_error(struct mailbox *box, enum mail_error *error_r)
 /* Wrapper for mail_storage_get_last_error(); */
 enum mail_error mailbox_get_last_mail_error(struct mailbox *box);
 
+const char * ATTR_NOWARN_UNUSED_RESULT
+mail_storage_get_last_internal_error(struct mail_storage *storage,
+				     enum mail_error *error_r) ATTR_NULL(2);
+/* Wrapper for mail_storage_get_last_internal_error(); */
+const char * ATTR_NOWARN_UNUSED_RESULT
+mailbox_get_last_internal_error(struct mailbox *box,
+				enum mail_error *error_r) ATTR_NULL(2);
+
 /* Save the last error until it's popped. This is useful for cases where the
    storage has already failed, but the cleanup code path changes the error to
    something else unwanted. */