Extract dtype.type in wrapper

If a key to the template metaclass is a numpy dtype object, use
the dtype.type result as the template class lookup key.

python/lsst/utils/wrappers.py

@@ -25,6 +25,8 @@
 import sys
 import types
 
+import numpy as np
+
 __all__ = ("continueClass", "inClass", "TemplateMeta")
 
 
@@ -265,8 +267,18 @@ def __call__(self, *args, **kwds):
         # the abstract base class.
         # If the ABC defines a "TEMPLATE_PARAMS" attribute, we use those strings
         # as the kwargs we should intercept to find the right type.
-        key = tuple(kwds.pop(p, d) for p, d in zip(self.TEMPLATE_PARAMS,
-                                                   self.TEMPLATE_DEFAULTS))
+
+        # Generate a type mapping key from input keywords. If the type returned
+        # from the keyword lookup is a numpy dtype object, fetch the underlying
+        # type of the dtype
+        key = []
+        for p, d in zip(self.TEMPLATE_PARAMS, self.TEMPLATE_DEFAULTS):
+            tempKey = kwds.pop(p, d)
+            if isinstance(tempKey, np.dtype):
+                tempKey = tempKey.type
+            key.append(tempKey)
+        key = tuple(key)
+
         # indices are only tuples if there are multiple elements
         cls = self._registry.get(key[0] if len(key) == 1 else key, None)
         if cls is None:

tests/test_wrappers.py

@@ -163,10 +163,14 @@ def testInheritanceHooks(self):
 
     def testConstruction(self):
         self.register()
-        f = self.Example(dtype=np.float32)
-        self.assertIsInstance(f, self.Example)
-        self.assertIsInstance(f, self.ExampleF)
-        self.assertNotIsInstance(f, self.ExampleD)
+        f1 = self.Example(dtype=np.float32)
+        # Test that numpy dtype objects resolve to their underlying type
+        f2 = self.Example(dtype=np.dtype(np.float32))
+        for f in (f1, f2):
+            self.assertIsInstance(f, self.Example)
+            self.assertIsInstance(f, self.ExampleF)
+            self.assertNotIsInstance(f, self.ExampleD)
+
         with self.assertRaises(TypeError):
             self.Example()
         with self.assertRaises(TypeError):