Add method for checking OS version.

src/openflexure_microscope_server/things/system.py

@@ -5,6 +5,7 @@ the microscope, server, and thing states to the web API.
 """
 
 import os
+import re
 import socket
 import subprocess
 import time
@@ -22,6 +23,8 @@ from openflexure_microscope_server.utilities import VersionData, robust_version_
 SHUTDOWN_CMD = ["sudo", "shutdown", "-h", "now"]
 REBOOT_CMD = ["sudo", "shutdown", "-r", "now"]
 
+OS_VERSION_FILE = "/usr/lib/os-release"
+
 
 class CommandOutput(BaseModel):
     """A pydantic model passing the STDOUT and STDERR from a subprocess over HTTP."""
@@ -81,6 +84,24 @@ class OpenFlexureSystem(lt.Thing):
         """Return True if running on a Raspberry Pi."""
         return os.path.exists("/usr/bin/raspi-config")
 
+    @lt.property
+    def os_version(self) -> Optional[str]:
+        """Return the OS version of the Pi. Returns None if not on a Pi."""
+        if not self.is_raspberrypi:
+            return None
+
+        if not os.path.isfile(OS_VERSION_FILE):
+            return "unknown"
+
+        with open(OS_VERSION_FILE, "r", encoding="utf-8") as os_file:
+            os_data = os_file.read()
+
+        version_match = re.search(r"^VERSION_CODENAME=(.+)$", os_data, re.MULTILINE)
+        if not version_match:
+            return "unknown"
+
+        return version_match.group(1)
+
     @lt.action
     def shutdown(self) -> CommandOutput:
         """Attempt to shutdown the device."""

tests/unit_tests/assets/os-release

@@ -0,0 +1,10 @@
+PRETTY_NAME="Debian GNU/Linux 13 (trixie)"
+NAME="Debian GNU/Linux"
+VERSION_ID="13"
+VERSION="13 (trixie)"
+VERSION_CODENAME=trixie
+DEBIAN_VERSION_FULL=13.4
+ID=debian
+HOME_URL="https://www.debian.org/"
+SUPPORT_URL="https://www.debian.org/support"
+BUG_REPORT_URL="https://bugs.debian.org/"

tests/unit_tests/assets/os-release-broken

@@ -0,0 +1 @@
+This doesn't contain the data we are looking for.

tests/unit_tests/test_system_thing.py

@@ -11,6 +11,11 @@ from labthings_fastapi.testing import create_thing_without_server
 from openflexure_microscope_server.things import system
 from openflexure_microscope_server.utilities import VersionData, robust_version_strings
 
+THIS_DIR = os.path.dirname(os.path.abspath(__file__))
+FAKE_OS_FILE = os.path.join(THIS_DIR, "assets", "os-release")
+BROKEN_OS_FILE = os.path.join(THIS_DIR, "assets", "os-release-broken")
+MISSING_OS_FILE = os.path.join(THIS_DIR, "assets", "this-does-not-exist")
+
 
 @pytest.fixture
 def system_thing():
@@ -37,6 +42,33 @@ def test_is_raspberry(system_thing):
     assert system_thing.is_raspberrypi == _is_raspberrypi()
 
 
+@pytest.mark.parametrize(
+    ("version_file", "expected_result"),
+    [
+        (MISSING_OS_FILE, "unknown"),
+        (FAKE_OS_FILE, "trixie"),
+        (BROKEN_OS_FILE, "unknown"),
+    ],
+)
+def test_os_version_pi(version_file, expected_result, system_thing, mocker):
+    """Check reading the operating system version from a Pi (mocked!)."""
+    type(system_thing).is_raspberrypi = mocker.PropertyMock(return_value=True)
+
+    mocker.patch(
+        "openflexure_microscope_server.things.system.OS_VERSION_FILE", version_file
+    )
+    assert system_thing.os_version == expected_result
+
+
+def test_os_version_not_pi(system_thing, mocker):
+    """Check reading the operating system when not on a Pi returns None."""
+    mocker.patch(
+        "openflexure_microscope_server.things.system.OS_VERSION_FILE", FAKE_OS_FILE
+    )
+    type(system_thing).is_raspberrypi = mocker.PropertyMock(return_value=False)
+    assert system_thing.os_version is None
+
+
 def test_version_data(system_thing):
     """Check VersionData is returned.