backends: add a new "none" backend

It can only be used for projects that don't have any rules at all, i.e.
they are purely using Meson to:

- configure files
- run (script?) tests
- install files that exist by the end of the setup stage

This can be useful e.g. for Meson itself, a pure python project.

1 files changed, 31 insertions, 0 deletions

diff --git a/mesonbuild/backend/nonebackend.py b/mesonbuild/backend/nonebackend.py
new file mode 100644
index 0000000..cf7c3dd
--- /dev/null
+++ b/mesonbuild/backend/nonebackend.py
@@ -0,0 +1,31 @@
+# Copyright 2022 The Meson development team
+
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+
+#     http://www.apache.org/licenses/LICENSE-2.0
+
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+from __future__ import annotations
+
+from .backends import Backend
+from .. import mlog
+from ..mesonlib import MesonBugException
+
+
+class NoneBackend(Backend):
+
+    name = 'none'
+
+    def generate(self):
+        if self.build.get_targets():
+            raise MesonBugException('None backend cannot generate target rules, but should have failed earlier.')
+        mlog.log('Generating simple install-only backend')
+        self.serialize_tests()
+        self.create_install_data_files()