driver: add initial type hints for common driver code

Add `ty` as a development dependency and configure it to check one
initial driver module.

Annotate `labgrid.driver.common` while leaving existing attrs-based
exception behavior unchanged.

Signed-off-by: Rainer Poisel <rainer@embedded-focus.com>

Author: rpoisel

labgrid/driver/common.py

@@ -1,7 +1,11 @@
 import logging
 import subprocess
+from typing import cast
+
 import attr
 
+from labgrid.resource.common import Resource
+
 from ..binding import BindingError, BindingMixin
 from .exception import ExecutionError
 
@@ -21,17 +25,17 @@ class Driver(BindingMixin):
     - deactivate
     """
 
-    def __attrs_post_init__(self):
+    def __attrs_post_init__(self) -> None:
         super().__attrs_post_init__()
         if self.target is None:
-            raise BindingError("Drivers can only be created on a valid target")
+            raise BindingError("Drivers can only be created on a valid target")  # ty: ignore[too-many-positional-arguments]
 
         logger_name = f"{self.__class__.__name__}({self.target.name})"
         if self.name:
             logger_name += f":{self.name}"
         self.logger = logging.getLogger(logger_name)
 
-    def get_priority(self, protocol):
+    def get_priority(self, protocol) -> int:
         """Retrieve the priority for a given protocol
 
         Arguments:
@@ -41,17 +45,17 @@ def get_priority(self, protocol):
             Int: value of the priority if it is found, 0 otherwise.
         """
         for cls in self.__class__.__mro__:
-            prios = getattr(cls, 'priorities', {})
+            prios = getattr(cls, "priorities", {})
             # we found a matching parent priorities attribute with the matching protocol
             if prios and protocol in prios:
-                return prios.get(protocol)
+                return cast(int, prios[protocol])
             # If we find the parent protocol, set the priority to 0
             if cls.__name__ == protocol.__name__:
                 return 0
 
         return 0
 
-    def get_export_name(self):
+    def get_export_name(self) -> str:
         """Get the name to be used for exported variables.
 
         Falls back to the class name if the driver has no name.
@@ -60,29 +64,32 @@ def get_export_name(self):
             return self.name
         return self.__class__.__name__
 
-    def get_export_vars(self):
+    def get_export_vars(self) -> dict[str, str]:
         """Get a dictionary of variables to be exported."""
         return {}
 
     @property
-    def skip_deactivate_on_export(self):
+    def skip_deactivate_on_export(self) -> bool:
         """Drivers are deactivated on export by default.
 
         If the driver can handle external accesses even while active, it can
         return True here.
         """
         return False
 
-    def get_bound_resources(self):
+    def get_bound_resources(self) -> set[Resource]:
         """Return the bound resources for a driver
 
         This recursively calls all suppliers and combines the sets of returned resources.
         """
-        res = set()
+        res: set[Resource] = set()
         for supplier in self.suppliers:
             res |= supplier.get_bound_resources()
         return res
 
-def check_file(filename, *, command_prefix=[]):
-    if subprocess.call(command_prefix + ['test', '-r', filename]) != 0:
-        raise ExecutionError(f"File {filename} is not readable")
+
+def check_file(filename, *, command_prefix=None) -> None:
+    if command_prefix is None:
+        command_prefix: list[str] = []
+    if subprocess.call(command_prefix + ["test", "-r", filename]) != 0:
+        raise ExecutionError(f"File {filename} is not readable")  # ty: ignore[too-many-positional-arguments]

pyproject.toml

@@ -91,6 +91,7 @@ dev = [
     "pytest-mock>=3.6.1",
     "pylint>=3.0.0",
     "ruff>=0.5.7",
+    "ty>=0.0.64",
     "pystuck",
     "requests[socks]>=2.26.0",
 
@@ -138,6 +139,11 @@ testpaths = [
 ]
 addopts = "-p no:labgrid"
 
+[tool.ty.src]
+include = [
+    "labgrid/driver/common.py",
+]
+
 [tool.pylint.imports]
 ignored-modules = ["gi"]
 
@@ -224,6 +230,7 @@ include = [
   "examples/**/*.py",
   "labgrid/driver/httpvideodriver.py",
   "labgrid/driver/manualswitchdriver.py",
+  "labgrid/driver/common.py",
   "labgrid/driver/power/gude8031.py",
   "labgrid/driver/power/pe6216.py",
   "labgrid/driver/power/poe_netgear_plus.py",

tests/test_driver_common.py

@@ -0,0 +1,45 @@
+from unittest.mock import Mock
+
+import pytest
+
+from labgrid import Target
+from labgrid.binding import BindingError
+from labgrid.driver.common import Driver, check_file
+from labgrid.driver.exception import ExecutionError
+
+
+def test_driver_requires_target() -> None:
+    with pytest.raises(BindingError):
+        Driver(None, None)
+
+
+def test_driver_get_priority_returns_zero_for_unknown_protocol(target: Target) -> None:
+    class Protocol:
+        pass
+
+    driver = Driver(target, None)
+
+    assert driver.get_priority(Protocol) == 0
+
+
+def test_driver_get_export_vars_returns_empty_dict(target: Target) -> None:
+    driver = Driver(target, None)
+
+    assert driver.get_export_vars() == {}
+
+
+def test_check_file_uses_default_command_prefix(monkeypatch: pytest.MonkeyPatch) -> None:
+    call = Mock(return_value=0)
+    monkeypatch.setattr("labgrid.driver.common.subprocess.call", call)
+
+    check_file("/tmp/file")
+
+    call.assert_called_once_with(["test", "-r", "/tmp/file"])
+
+
+def test_check_file_raises_execution_error(monkeypatch: pytest.MonkeyPatch) -> None:
+    call = Mock(return_value=1)
+    monkeypatch.setattr("labgrid.driver.common.subprocess.call", call)
+
+    with pytest.raises(ExecutionError, match="File /tmp/file is not readable"):
+        check_file("/tmp/file")