Load user-installed interface modules only on demand if importlib is not installed

Author: wbarnha

can/interface.py

@@ -18,7 +18,7 @@
 log_autodetect = log.getChild("detect_available_configs")
 
 
-def _get_class_for_interface(interface: str) -> Type[BusABC]:
+def _get_class_for_interface(interface: str, installed_interfaces: dict = None) -> Type[BusABC]:
     """
     Returns the main bus class for the given interface.
 
@@ -28,8 +28,10 @@ def _get_class_for_interface(interface: str) -> Type[BusABC]:
          if there was a problem while importing the interface or the bus class within that
     """
     # Find the correct backend
+    if not isinstance(installed_interfaces, dict):
+        installed_interfaces = BACKENDS
     try:
-        module_name, class_name = BACKENDS[interface]
+        module_name, class_name = installed_interfaces[interface]
     except KeyError:
         raise NotImplementedError(
             "CAN interface '{}' not supported".format(interface)
@@ -149,6 +151,13 @@ def detect_available_configs(
 
     # Figure out where to search
     if interfaces is None:
+        try:
+            from importlib.metadata import entry_points  # If this works, the interfaces have probably been loaded
+        except ImportError:
+            from pkg_resources import iter_entry_points as entry_points
+            entry = entry_points("can.interface")
+            BACKENDS.update({interface.name: (interface.module_name, interface.attrs[0])
+                             for interface in entry})
         interfaces = BACKENDS
     elif isinstance(interfaces, str):
         interfaces = (interfaces,)
@@ -158,7 +167,7 @@ def detect_available_configs(
     for interface in interfaces:
 
         try:
-            bus_class = _get_class_for_interface(interface)
+            bus_class = _get_class_for_interface(interface, installed_interfaces=BACKENDS)
         except CanInterfaceNotImplementedError:
             log_autodetect.debug(
                 'interface "%s" cannot be loaded for detection of available configurations',

can/interfaces/__init__.py

@@ -33,8 +33,9 @@
     if 'can.interface' in entry:
         BACKENDS.update({interface.name: tuple(interface.value.split(':')) for interface in entry['can.interface']})
 except ImportError:
-    from pkg_resources import iter_entry_points as entry_points
-    entry = entry_points("can.interface")
-    BACKENDS.update({interface.name: (interface.module_name, interface.attrs[0]) for interface in entry})
+    # from pkg_resources import iter_entry_points as entry_points
+    # entry = entry_points("can.interface")
+    # BACKENDS.update({interface.name: (interface.module_name, interface.attrs[0]) for interface in entry})
+    pass
 
 VALID_INTERFACES = frozenset(list(BACKENDS.keys()))

can/util.py

@@ -15,7 +15,7 @@
 from configparser import ConfigParser
 
 import can
-from .interfaces import VALID_INTERFACES
+from .interfaces import VALID_INTERFACES, BACKENDS
 from . import typechecking
 from .exceptions import CanInterfaceNotImplementedError
 
@@ -207,10 +207,19 @@ def _create_bus_config(config: Dict[str, Any]) -> typechecking.BusConfig:
         if key not in config:
             config[key] = None
 
-    if config["interface"] not in VALID_INTERFACES:
-        raise CanInterfaceNotImplementedError(
-            f'Unknown interface type "{config["interface"]}"'
-        )
+    # if config["interface"] not in VALID_INTERFACES:
+    if config["interface"] not in BACKENDS.keys():
+        try:
+            from importlib.metadata import entry_points  # If this works, the interfaces have probably been loaded
+        except ImportError:
+            from pkg_resources import iter_entry_points as entry_points
+            entry = entry_points("can.interface")
+            BACKENDS.update({interface.name: (interface.module_name, interface.attrs[0])
+                             for interface in entry})
+        if config["interface"] not in BACKENDS.keys():
+            raise CanInterfaceNotImplementedError(
+                f'Unknown interface type "{config["interface"]}"'
+            )
 
     if "bitrate" in config:
         config["bitrate"] = int(config["bitrate"])