fix: skip prefix creation when running native Linux executables (#302)

* umu_run: skip prefix setup when not using proton

* umu_run: update environment check logic when not using proton

* umu_test: add tests when configured to not using proton

umu/umu_run.py

@@ -72,6 +72,9 @@ def setup_pfx(path: str) -> None:
     user: str = getpwuid(os.getuid()).pw_name
     wineuser: Path = Path(path).expanduser().joinpath("drive_c", "users", user)
 
+    if os.environ.get("UMU_NO_PROTON") == "1":
+        return
+
     if pfx.is_symlink():
         pfx.unlink()
 
@@ -112,17 +115,23 @@ def check_env(
         err: str = "Environment variable is empty: WINEPREFIX"
         raise ValueError(err)
 
-    if "WINEPREFIX" not in os.environ:
+    if (
+        os.environ.get("UMU_NO_PROTON") != "1"
+        and "WINEPREFIX" not in os.environ
+    ):
         pfx: Path = Path.home().joinpath("Games", "umu", env["GAMEID"])
         pfx.mkdir(parents=True, exist_ok=True)
         os.environ["WINEPREFIX"] = str(pfx)
 
-    if not Path(os.environ["WINEPREFIX"]).expanduser().is_dir():
+    if (
+        os.environ.get("UMU_NO_PROTON") != "1"
+        and not Path(os.environ["WINEPREFIX"]).expanduser().is_dir()
+    ):
         pfx: Path = Path(os.environ["WINEPREFIX"])
         pfx.mkdir(parents=True, exist_ok=True)
         os.environ["WINEPREFIX"] = str(pfx)
 
-    env["WINEPREFIX"] = os.environ["WINEPREFIX"]
+    env["WINEPREFIX"] = os.environ.get("WINEPREFIX", "")
 
     # Skip Proton if running a native Linux executable
     if os.environ.get("UMU_NO_PROTON") == "1":

umu/umu_test.py

@@ -69,6 +69,7 @@ def setUp(self):
             "STEAM_COMPAT_MEDIA_PATH": "",
             "STEAM_FOSSILIZE_DUMP_PATH": "",
             "DXVK_STATE_CACHE_PATH": "",
+            "UMU_NO_PROTON": "",
         }
         self.user = getpwuid(os.getuid()).pw_name
         self.test_opts = "-foo -bar"
@@ -2914,6 +2915,26 @@ def test_setup_pfx_paths(self):
             "Expected tracked_files to be a file",
         )
 
+    def test_setup_pfx_noproton(self):
+        """Test setup_pfx when configured to not use Proton."""
+        result = None
+        os.environ["UMU_NO_PROTON"] = "1"
+
+        result = umu_run.setup_pfx(self.test_file)
+        self.assertTrue(result is None, f"Expected None, received {result}")
+        self.assertFalse(
+            Path(self.test_file, "pfx").exists(),
+            f"Expected {self.test_file}/pfx to not exist",
+        )
+        self.assertFalse(
+            Path(self.test_file, "tracked_files").exists(),
+            f"Expected {self.test_file}/tracked_files to not exist",
+        )
+        self.assertFalse(
+            Path(self.test_file, "drive_c").exists(),
+            f"Expected {self.test_file}/drive_c to not exist",
+        )
+
     def test_setup_pfx(self):
         """Test setup_pfx."""
         result = None
@@ -3034,6 +3055,62 @@ def test_parse_args_config(self):
                 result, Namespace, "Expected a Namespace from parse_arg"
             )
 
+    def test_env_nowine_noproton(self):
+        """Test check_env when configured to not use Proton.
+
+        Expects the directory $HOME/Games/umu/$GAMEID to not be created
+        when UMU_NO_PROTON=1 and GAMEID is set in the host environment.
+        """
+        result = None
+        # Mock $HOME
+        mock_home = Path(self.test_file)
+
+        with (
+            ThreadPoolExecutor() as thread_pool,
+            # Mock the internal call to Path.home(). Otherwise, some of our
+            # assertions may fail when running this test suite locally if
+            # the user already has that dir
+            patch.object(Path, "home", return_value=mock_home),
+        ):
+            os.environ["UMU_NO_PROTON"] = "1"
+            os.environ["GAMEID"] = "foo"
+            result = umu_run.check_env(self.env, thread_pool)
+            self.assertTrue(result is self.env)
+            path = mock_home.joinpath("Games", "umu", os.environ["GAMEID"])
+            # Ensure we did not create the target nor its parents up to $HOME
+            self.assertFalse(path.exists(), f"Expected {path} to not exist")
+            self.assertFalse(
+                path.parent.exists(), f"Expected {path.parent} to not exist"
+            )
+            self.assertFalse(
+                path.parent.parent.exists(),
+                f"Expected {path.parent.parent} to not exist",
+            )
+            self.assertTrue(
+                mock_home.exists(), f"Expected {mock_home} to exist"
+            )
+
+    def test_env_wine_noproton(self):
+        """Test check_env when configured to not use Proton.
+
+        Expects the WINE prefix directory to not be created when
+        UMU_NO_PROTON=1 and WINEPREFIX is set in the host environment.
+        """
+        result = None
+
+        with (
+            ThreadPoolExecutor() as thread_pool,
+        ):
+            os.environ["WINEPREFIX"] = "123"
+            os.environ["UMU_NO_PROTON"] = "1"
+            os.environ["GAMEID"] = "foo"
+            result = umu_run.check_env(self.env, thread_pool)
+            self.assertTrue(result is self.env)
+            self.assertFalse(
+                Path(os.environ["WINEPREFIX"]).exists(),
+                f"Expected directory {os.environ['WINEPREFIX']} to not exist",
+            )
+
     def test_env_proton_nodir(self):
         """Test check_env when $PROTONPATH in the case we failed to set it.