Allow to define a container_runtime_path

Add a few tests for this along the way, and update the end-user messages
about Docker/Podman to account for this change.

dangerzone/container_utils.py

@@ -1,4 +1,5 @@
 import logging
+import os
 import platform
 import shutil
 import subprocess
@@ -14,14 +15,27 @@ log = logging.getLogger(__name__)
 
 
 def get_runtime_name() -> str:
-    if platform.system() == "Linux":
+    settings = Settings()
-        runtime_name = "podman"
+    try:
-    else:
+        runtime_name = settings.get("container_runtime")
-        # Windows, Darwin, and unknown use docker for now, dangerzone-vm eventually
+    except KeyError:
-        runtime_name = "docker"
+        return "podman" if platform.system() == "Linux" else "docker"
     return runtime_name
 
 
+def get_runtime() -> str:
+    container_tech = get_runtime_name()
+    runtime = shutil.which(container_tech)
+    if runtime is None:
+        # Fallback to the container runtime path from the settings
+        settings = Settings()
+        runtime_path = settings.get("container_runtime_path")
+        if os.path.exists(runtime_path):
+            return runtime_path
+        raise errors.NoContainerTechException(container_tech)
+    return runtime
+
+
 def get_runtime_version() -> Tuple[int, int]:
     """Get the major/minor parts of the Docker/Podman version.
 
@@ -32,13 +46,14 @@ def get_runtime_version() -> Tuple[int, int]:
     semver parser is an overkill.
     """
     # Get the Docker/Podman version, using a Go template.
-    runtime = get_runtime_name()
+    runtime_name = get_runtime_name()
-    if runtime == "podman":
+
+    if runtime_name == "podman":
         query = "{{.Client.Version}}"
     else:
         query = "{{.Server.Version}}"
 
-    cmd = [runtime, "version", "-f", query]
+    cmd = [get_runtime(), "version", "-f", query]
     try:
         version = subprocess.run(
             cmd,
@@ -47,7 +62,7 @@ def get_runtime_version() -> Tuple[int, int]:
             check=True,
         ).stdout.decode()
     except Exception as e:
-        msg = f"Could not get the version of the {runtime.capitalize()} tool: {e}"
+        msg = f"Could not get the version of the {runtime_name.capitalize()} tool: {e}"
         raise RuntimeError(msg) from e
 
     # Parse this version and return the major/minor parts, since we don't need the
@@ -57,20 +72,12 @@ def get_runtime_version() -> Tuple[int, int]:
         return (int(major), int(minor))
     except Exception as e:
         msg = (
-            f"Could not parse the version of the {runtime.capitalize()} tool"
+            f"Could not parse the version of the {runtime_name.capitalize()} tool"
             f" (found: '{version}') due to the following error: {e}"
         )
         raise RuntimeError(msg)
 
 
-def get_runtime() -> str:
-    container_tech = get_runtime_name()
-    runtime = shutil.which(container_tech)
-    if runtime is None:
-        raise errors.NoContainerTechException(container_tech)
-    return runtime
-
-
 def list_image_tags() -> List[str]:
     """Get the tags of all loaded Dangerzone images.
 

dangerzone/gui/main_window.py

@@ -574,8 +574,15 @@ class WaitingWidgetContainer(WaitingWidget):
             self.finished.emit()
 
     def state_change(self, state: str, error: Optional[str] = None) -> None:
+        custom_runtime = self.dangerzone.settings.custom_runtime_specified()
+
         if state == "not_installed":
-            if platform.system() == "Linux":
+            if custom_runtime:
+                self.show_error(
+                    "<strong>We could not find the container runtime defined in your settings</strong><br><br>"
+                    "Please check your settings, install it if needed, and retry."
+                )
+            elif platform.system() == "Linux":
                 self.show_error(
                     "<strong>Dangerzone requires Podman</strong><br><br>"
                     "Install it and retry."
@@ -588,7 +595,12 @@ class WaitingWidgetContainer(WaitingWidget):
                 )
 
         elif state == "not_running":
-            if platform.system() == "Linux":
+            if custom_runtime:
+                self.show_error(
+                    "<strong>We were unable to start the container runtime defined in your settings</strong><br><br>"
+                    "Please check your settings, install it if needed, and retry."
+                )
+            elif platform.system() == "Linux":
                 # "not_running" here means that the `podman image ls` command failed.
                 message = (
                     "<strong>Dangerzone requires Podman</strong><br><br>"

dangerzone/isolation_provider/container.py

@@ -143,7 +143,10 @@ class Container(IsolationProvider):
     def check_docker_desktop_version(self) -> Tuple[bool, str]:
         # On windows and darwin, check that the minimum version is met
         version = ""
-        if platform.system() != "Linux":
+        runtime_is_docker = container_utils.get_runtime_name() == "docker"
+        platform_is_not_linux = platform.system() != "Linux"
+
+        if runtime_is_docker and platform_is_not_linux:
             with subprocess.Popen(
                 ["docker", "version", "--format", "{{.Server.Platform.Name}}"],
                 stdout=subprocess.PIPE,

dangerzone/settings.py

@@ -10,76 +10,84 @@ from .util import get_config_dir, get_version
 
 log = logging.getLogger(__name__)
 
-SETTINGS_FILENAME = get_config_dir() / "settings.json"
+SETTINGS_FILENAME: str = "settings.json"
-
-SETTINGS: dict = {}
 
 
-def generate_default_settings() -> Dict[str, Any]:
+class Settings:
-    return {
+    settings: Dict[str, Any]
-        "save": True,
-        "archive": True,
-        "ocr": True,
-        "ocr_language": "English",
-        "open": True,
-        "open_app": None,
-        "safe_extension": SAFE_EXTENSION,
-        "updater_check": None,
-        "updater_last_check": None,  # last check in UNIX epoch (secs since 1970)
-        # FIXME: How to invalidate those if they change upstream?
-        "updater_latest_version": get_version(),
-        "updater_latest_changelog": "",
-        "updater_errors": 0,
-    }
 
+    def __init__(self) -> None:
+        self.settings_filename = get_config_dir() / SETTINGS_FILENAME
+        self.default_settings: Dict[str, Any] = self.generate_default_settings()
+        self.load()
 
-def get(key: str) -> Any:
+    @classmethod
-    return SETTINGS[key]
+    def generate_default_settings(cls) -> Dict[str, Any]:
+        return {
+            "save": True,
+            "archive": True,
+            "ocr": True,
+            "ocr_language": "English",
+            "open": True,
+            "open_app": None,
+            "safe_extension": SAFE_EXTENSION,
+            "updater_check": None,
+            "updater_last_check": None,  # last check in UNIX epoch (secs since 1970)
+            # FIXME: How to invalidate those if they change upstream?
+            "updater_latest_version": get_version(),
+            "updater_latest_changelog": "",
+            "updater_errors": 0,
+        }
 
+    def custom_runtime_specified(self) -> bool:
+        return "container_runtime" in self.settings
 
-def set(key: str, val: Any, autosave: bool = False) -> None:
+    def get(self, key: str) -> Any:
-    try:
+        return self.settings[key]
-        old_val = SETTINGS.get(key)
-    except KeyError:
-        old_val = None
-    SETTINGS[key] = val
-    if autosave and val != old_val:
-        save()
 
-
+    def set(self, key: str, val: Any, autosave: bool = False) -> None:
-def get_updater_settings() -> Dict[str, Any]:
-    return {key: val for key, val in SETTINGS.items() if key.startswith("updater_")}
-
-
-def load() -> None:
-    default_settings = default_settings()
-    if SETTINGS_FILENAME.is_file():
-        # If the settings file exists, load it
         try:
-            with SETTINGS_FILENAME.open("r") as settings_file:
+            old_val = self.get(key)
-                SETTINGS = json.load(settings_file)
+        except KeyError:
+            old_val = None
+        self.settings[key] = val
+        if autosave and val != old_val:
+            self.save()
 
-            # If it's missing any fields, add them from the default settings
+    def get_updater_settings(self) -> Dict[str, Any]:
-            for key in default_settings:
+        return {
-                if key not in SETTINGS:
+            key: val for key, val in self.settings.items() if key.startswith("updater_")
-                    SETTINGS[key] = default_settings[key]
+        }
-                elif key == "updater_latest_version":
-                    if version.parse(get_version()) > version.parse(get(key)):
-                        set(key, get_version())
 
-        except Exception:
+    def load(self) -> None:
-            log.error("Error loading settings, falling back to default")
+        if os.path.isfile(self.settings_filename):
-            SETTINGS = default_settings
+            self.settings = self.default_settings
 
-    else:
+            # If the settings file exists, load it
-        # Save with default settings
+            try:
-        log.info("Settings file doesn't exist, starting with default")
+                with open(self.settings_filename, "r") as settings_file:
-        SETTINGS = default_settings
+                    self.settings = json.load(settings_file)
 
-    save()
+                # If it's missing any fields, add them from the default settings
+                for key in self.default_settings:
+                    if key not in self.settings:
+                        self.settings[key] = self.default_settings[key]
+                    elif key == "updater_latest_version":
+                        if version.parse(get_version()) > version.parse(self.get(key)):
+                            self.set(key, get_version())
 
+            except Exception:
+                log.error("Error loading settings, falling back to default")
+                self.settings = self.default_settings
 
-def save() -> None:
+        else:
-    SETTINGS_FILENAME.parent.mkdir(parents=True, exist_ok=True)
+            # Save with default settings
-    with SETTINGS_FILENAME.open("w") as settings_file:
+            log.info("Settings file doesn't exist, starting with default")
-        json.dump(SETTINGS, settings_file, indent=4)
+            self.settings = self.default_settings
+
+        self.save()
+
+    def save(self) -> None:
+        self.settings_filename.parent.mkdir(parents=True, exist_ok=True)
+        with self.settings_filename.open("w") as settings_file:
+            json.dump(self.settings, settings_file, indent=4)

tests/gui/conftest.py

@@ -21,34 +21,25 @@ def get_qt_app() -> Application:
 
 def generate_isolated_updater(
     tmp_path: Path,
-    monkeypatch: MonkeyPatch,
+    mocker: MockerFixture,
-    app_mocker: Optional[MockerFixture] = None,
+    mock_app: bool = False,
 ) -> UpdaterThread:
     """Generate an Updater class with its own settings."""
-    if app_mocker:
+    app = mocker.MagicMock() if mock_app else get_qt_app()
-        app = app_mocker.MagicMock()
-    else:
-        app = get_qt_app()
 
     dummy = Dummy()
-    # XXX: We can monkey-patch global state without wrapping it in a context manager, or
+    mocker.patch("dangerzone.settings.get_config_dir", return_value=tmp_path)
-    # worrying that it will leak between tests, for two reasons:
+
-    #
-    # 1. Parallel tests in PyTest take place in different processes.
-    # 2. The monkeypatch fixture tears down the monkey-patch after each test ends.
-    monkeypatch.setattr(util, "get_config_dir", lambda: tmp_path)
     dangerzone = DangerzoneGui(app, isolation_provider=dummy)
     updater = UpdaterThread(dangerzone)
     return updater
 
 
 @pytest.fixture
-def updater(
+def updater(tmp_path: Path, mocker: MockerFixture) -> UpdaterThread:
-    tmp_path: Path, monkeypatch: MonkeyPatch, mocker: MockerFixture
+    return generate_isolated_updater(tmp_path, mocker, mock_app=True)
-) -> UpdaterThread:
-    return generate_isolated_updater(tmp_path, monkeypatch, mocker)
 
 
 @pytest.fixture
-def qt_updater(tmp_path: Path, monkeypatch: MonkeyPatch) -> UpdaterThread:
+def qt_updater(tmp_path: Path, mocker: MockerFixture) -> UpdaterThread:
-    return generate_isolated_updater(tmp_path, monkeypatch)
+    return generate_isolated_updater(tmp_path, mocker, mock_app=False)

tests/gui/test_updater.py

@@ -48,9 +48,7 @@ def test_default_updater_settings(updater: UpdaterThread) -> None:
     )
 
 
-def test_pre_0_4_2_settings(
+def test_pre_0_4_2_settings(tmp_path: Path, mocker: MockerFixture) -> None:
-    tmp_path: Path, monkeypatch: MonkeyPatch, mocker: MockerFixture
-) -> None:
     """Check settings of installations prior to 0.4.2.
 
     Check that installations that have been upgraded from a version < 0.4.2 to >= 0.4.2
@@ -58,7 +56,7 @@ def test_pre_0_4_2_settings(
     in their settings.json file.
     """
     save_settings(tmp_path, default_settings_0_4_1())
-    updater = generate_isolated_updater(tmp_path, monkeypatch, mocker)
+    updater = generate_isolated_updater(tmp_path, mocker, mock_app=True)
     assert (
         updater.dangerzone.settings.get_updater_settings() == default_updater_settings()
     )
@@ -83,12 +81,10 @@ def test_post_0_4_2_settings(
     # version is 0.4.3.
     expected_settings = default_updater_settings()
     expected_settings["updater_latest_version"] = "0.4.3"
-    monkeypatch.setattr(
+    monkeypatch.setattr(settings, "get_version", lambda: "0.4.3")
-        settings, "get_version", lambda: expected_settings["updater_latest_version"]
-    )
 
     # Ensure that the Settings class will correct the latest version field to 0.4.3.
-    updater = generate_isolated_updater(tmp_path, monkeypatch, mocker)
+    updater = generate_isolated_updater(tmp_path, mocker, mock_app=True)
     assert updater.dangerzone.settings.get_updater_settings() == expected_settings
 
     # Simulate an updater check that found a newer Dangerzone version (e.g., 0.4.4).
@@ -118,9 +114,7 @@ def test_linux_no_check(updater: UpdaterThread, monkeypatch: MonkeyPatch) -> Non
     assert updater.dangerzone.settings.get_updater_settings() == expected_settings
 
 
-def test_user_prompts(
+def test_user_prompts(updater: UpdaterThread, mocker: MockerFixture) -> None:
-    updater: UpdaterThread, monkeypatch: MonkeyPatch, mocker: MockerFixture
-) -> None:
     """Test prompting users to ask them if they want to enable update checks."""
     # First run
     #
@@ -370,8 +364,6 @@ def test_update_errors(
 def test_update_check_prompt(
     qtbot: QtBot,
     qt_updater: UpdaterThread,
-    monkeypatch: MonkeyPatch,
-    mocker: MockerFixture,
 ) -> None:
     """Test that the prompt to enable update checks works properly."""
     # Force Dangerzone to check immediately for updates

tests/isolation_provider/test_container.py

@@ -87,7 +87,7 @@ class TestContainer(IsolationProviderTest):
     ) -> None:
         """When an image keep being not installed, it should return False"""
         fp.register_subprocess(
-            ["podman", "version", "-f", "{{.Client.Version}}"],
+            [container_utils.get_runtime(), "version", "-f", "{{.Client.Version}}"],
             stdout="4.0.0",
         )
 

tests/test_container_utils.py

@@ -0,0 +1,28 @@
+from pathlib import Path
+
+from pytest_mock import MockerFixture
+
+from dangerzone.container_utils import get_runtime_name
+from dangerzone.settings import Settings
+
+
+def test_get_runtime_name_from_settings(mocker: MockerFixture, tmp_path: Path) -> None:
+    mocker.patch("dangerzone.settings.get_config_dir", return_value=tmp_path)
+
+    settings = Settings()
+    settings.set("container_runtime", "new-kid-on-the-block", autosave=True)
+
+    assert get_runtime_name() == "new-kid-on-the-block"
+
+
+def test_get_runtime_name_linux(mocker: MockerFixture) -> None:
+    mocker.patch("platform.system", return_value="Linux")
+    assert get_runtime_name() == "podman"
+
+
+def test_get_runtime_name_non_linux(mocker: MockerFixture) -> None:
+    mocker.patch("platform.system", return_value="Windows")
+    assert get_runtime_name() == "docker"
+
+    mocker.patch("platform.system", return_value="Something else")
+    assert get_runtime_name() == "docker"

tests/test_settings.py

@@ -21,6 +21,13 @@ def default_settings_0_4_1() -> dict:
     }
 
 
+def save_settings(tmp_path: Path, settings: dict) -> None:
+    """Mimic the way Settings save a dictionary to a settings.json file."""
+    settings_filename = tmp_path / "settings.json"
+    with open(settings_filename, "w") as settings_file:
+        json.dump(settings, settings_file, indent=4)
+
+
 def test_no_settings_file_creates_new_one(
     tmp_path: Path,
     mocker: MockerFixture,