Fix classproperty issue

nkpro2000sr · bessman · commit 119fb02cd30e · 2021-08-02T14:50:31.000+02:00
diff --git a/pslab/bus/spi.py b/pslab/bus/spi.py
@@ -19,6 +19,7 @@
 0
 """
 
+import sys
 from typing import List, Tuple
 
 import pslab.protocol as CP
@@ -37,6 +38,21 @@
 _SMP = 1
 
 
+class classmethod_(classmethod):
+    """Support chaining classmethod and property."""
+
+    def __init__(self, f):
+        self.f = f
+        super().__init__(f)
+
+    def __get__(self, obj, cls=None):
+        # classmethod() to support chained decorators; new in python 3.9.
+        if sys.version_info < (3, 9) and isinstance(self.f, property):
+            return self.f.__get__(cls)
+        else:
+            return super().__get__(obj, cls)
+
+
 class _SPIPrimitive:
     """SPI primitive commands.
 
@@ -69,15 +85,15 @@ class _SPIPrimitive:
     def __init__(self, device: SerialHandler = None):
         self._device = device if device is not None else SerialHandler()
 
-    @classmethod
+    @classmethod_
     @property
     def _frequency(cls) -> float:
         ppre = cls._PPRE_MAP[cls._primary_prescaler]
         spre = cls._SPRE_MAP[cls._secondary_prescaler]
 
         return CP.CLOCK_RATE / (ppre * spre)
 
-    @classmethod
+    @classmethod_
     @property
     def _clock_phase(cls) -> int:
         return (cls._clock_edge ^ 1) & 1
