Merge pull request #117 from robberwick/not-connected-exception

feat: implement backend connection checks and add no_backend_required…

Author: robberwick

src/blinkstick/clients/blinkstick.py

@@ -12,8 +12,10 @@
     remap_rgb_value_reverse,
     ColorFormat,
 )
-from blinkstick.enums import BlinkStickVariant
+from blinkstick.decorators import no_backend_required
 from blinkstick.devices import BlinkStickDevice
+from blinkstick.enums import BlinkStickVariant
+from blinkstick.exceptions import NotConnected
 from blinkstick.utilities import string_to_info_block_data
 
 if sys.platform == "win32":
@@ -63,6 +65,19 @@ def __init__(
             self.backend = USBBackend(device)
             self.bs_serial = self.get_serial()
 
+    def __getattribute__(self, name):
+        """Default all callables to require a backend unless they have the no_backend_required attribute"""
+        attr = object.__getattribute__(self, name)
+        if callable(attr) and not getattr(attr, "no_backend_required", False):
+
+            def wrapper(*args, **kwargs):
+                if self.backend is None:
+                    raise NotConnected("No backend set")
+                return attr(*args, **kwargs)
+
+            return wrapper
+        return attr
+
     def get_serial(self) -> str:
         """
         Returns the serial number of backend.::

src/blinkstick/decorators.py

@@ -0,0 +1,15 @@
+from __future__ import annotations
+
+from functools import wraps
+
+
+def no_backend_required(func):
+    """no-op decorator to mark a function as requiring a backend. See BlinkStick.__getattribute__ for usage."""
+
+    func.no_backend_required = True
+
+    @wraps(func)
+    def wrapper(self, *args, **kwargs):
+        return func(self, *args, **kwargs)
+
+    return wrapper

src/blinkstick/exceptions.py

@@ -1,2 +1,9 @@
+from __future__ import annotations
+
+
 class BlinkStickException(Exception):
     pass
+
+
+class NotConnected(BlinkStickException):
+    pass

tests/clients/test_blinkstick.py

@@ -7,14 +7,32 @@
 from blinkstick.clients.blinkstick import BlinkStick
 from pytest_mock import MockFixture
 
+from blinkstick.exceptions import NotConnected
 from tests.conftest import make_blinkstick
 
 
 def test_instantiate():
+    """Test that we can instantiate a BlinkStick object."""
     bs = BlinkStick()
     assert bs is not None
 
 
+def test_all_methods_require_backend(make_blinkstick):
+    """Test that all methods require a backend."""
+    bs = make_blinkstick()
+    bs.backend = None  # noqa
+
+    class_methods = (
+        method
+        for method in dir(BlinkStick)
+        if callable(getattr(bs, method)) and not method.startswith("__")
+    )
+    for method_name in class_methods:
+        method = getattr(bs, method_name)
+        with pytest.raises(NotConnected):
+            method()
+
+
 @pytest.mark.parametrize(
     "serial, version_attribute, expected_variant, expected_variant_value",
     [