tests/py: Enable umockdev based tests

We re-exec the test case in pytest_configure if the LD_PRELOAD doesn't
contain libumockdev-preload.so. Even if the system doesn't have it, it
will show up in the environment and we can continue.

It also sets the UMOCKDEV_DIR env for the portal frontend. In theory
dbusmock should already do this for us but it doesn't seem to be
working.

Finally, it makes sure that ASAN keeps working even when LD_PRELOAD is
being used which is always the case because we require umockdev.

tests/__init__.py

@@ -334,7 +334,11 @@ class PortalMock:
     """
 
     def __init__(
-        self, dbus_test_case, portal_name: str, app_id: str = "org.example.App"
+        self,
+        dbus_test_case,
+        portal_name: str,
+        app_id: str = "org.example.App",
+        umockdev=None,
     ):
         self.dbus_test_case = dbus_test_case
         self.portal_name = portal_name
@@ -344,6 +348,7 @@ def __init__(
         self.portal_interfaces: Dict[str, dbus.Interface] = {}
         self.app_id = app_id
         self.busses = {dbusmock.BusType.SYSTEM: {}, dbusmock.BusType.SESSION: {}}
+        self.umockdev = umockdev
 
     @property
     def interface_name(self) -> str:
@@ -420,6 +425,22 @@ def mock_interface(self):
         )
         return dbus.Interface(obj, dbusmock.MOCK_IFACE)
 
+    def _maybe_add_asan_preload(self, executable, env):
+        # ASAN really wants to be the first library to get loaded but we also
+        # LD_PRELOAD umockdev and LD_PRELOAD gets loaded before any "normally"
+        # linked libraries. This uses ldd to find the version of libasan.so that
+        # should be loaded and puts it in front of LD_PRELOAD.
+        # This way, LD_PRELOAD and ASAN can be used at the same time.
+        ldd = subprocess.check_output(["ldd", executable]).decode("utf-8")
+        libs = [line.split()[0] for line in ldd.splitlines()]
+        try:
+            libasan = next(filter(lambda lib: lib.startswith("libasan"), libs))
+        except StopIteration:
+            return
+
+        preload = env.get("LD_PRELOAD", "")
+        env["LD_PRELOAD"] = f"{libasan}:{preload}"
+
     def start_xdp(self):
         """
         Start the xdg-desktop-portal process
@@ -437,6 +458,9 @@ def start_xdp(self):
         env["XDG_CURRENT_DESKTOP"] = "test"
         env["XDG_DESKTOP_PORTAL_TEST_APP_ID"] = self.app_id
 
+        if self.umockdev:
+            env["UMOCKDEV_DIR"] = self.umockdev.get_root_dir()
+
         asan_suppression = (
             Path(os.getenv("G_TEST_SRCDIR", "tests")) / "asan.suppression"
         )
@@ -471,6 +495,9 @@ def start_portal_frontend(self, env):
                 f"{portal_frontend} does not exist, try running from meson build dir or setting G_TEST_BUILDDIR"
             )
 
+        env = env.copy()
+        self._maybe_add_asan_preload(portal_frontend, env)
+
         portal_frontend = subprocess.Popen([portal_frontend], env=env)
 
         for _ in range(50):
@@ -510,6 +537,9 @@ def start_permission_store(self, env):
                 f"{permission_store_path} does not exist, try running from meson build dir or setting G_TEST_BUILDDIR"
             )
 
+        env = env.copy()
+        self._maybe_add_asan_preload(permission_store_path, env)
+
         permission_store = subprocess.Popen([permission_store_path], env=env)
 
         for _ in range(50):

tests/conftest.py

@@ -7,15 +7,25 @@
 import pytest
 import dbusmock
 import os
+import sys
 import tempfile
 
 from tests import PortalMock
 
 
 def pytest_configure():
+    ensure_umockdev_loaded()
     create_test_dirs()
 
 
+def ensure_umockdev_loaded():
+    umockdev_preload = "libumockdev-preload.so"
+    preload = os.environ.get("LD_PRELOAD", "")
+    if umockdev_preload not in preload:
+        os.environ["LD_PRELOAD"] = f"{umockdev_preload}:{preload}"
+        os.execv(sys.executable, [sys.executable] + sys.argv)
+
+
 def create_test_dirs():
     env_dirs = [
         "HOME",
@@ -123,14 +133,22 @@ def app_id():
     return "org.example.App"
 
 
+@pytest.fixture
+def umockdev():
+    """
+    Default fixture providing a umockdev testbed
+    """
+    return None
+
+
 @pytest.fixture
 def portal_mock(
-    dbus_test_case, portal_name, required_templates, template_params, app_id
+    dbus_test_case, portal_name, required_templates, template_params, app_id, umockdev
 ) -> PortalMock:
     """
     Fixture yielding a PortalMock object with the impl started, if applicable.
     """
-    pmock = PortalMock(dbus_test_case, portal_name, app_id)
+    pmock = PortalMock(dbus_test_case, portal_name, app_id, umockdev)
 
     for template, params in required_templates.items():
         params = template_params.get(template, params)