fixes #144

Author: jph00

fastcore/_nbdev.py

@@ -151,6 +151,7 @@
          "threaded": "02_utils.ipynb",
          "type_hints": "03_dispatch.ipynb",
          "anno_ret": "03_dispatch.ipynb",
+         "lenient_issubclass": "03_dispatch.ipynb",
          "sorted_topologically": "03_dispatch.ipynb",
          "TypeDispatch": "03_dispatch.ipynb",
          "DispatchReg": "03_dispatch.ipynb",

fastcore/dispatch.py

@@ -1,7 +1,7 @@
 # AUTOGENERATED! DO NOT EDIT! File to edit: nbs/03_dispatch.ipynb (unless otherwise specified).
 
-__all__ = ['type_hints', 'anno_ret', 'sorted_topologically', 'TypeDispatch', 'DispatchReg', 'typedispatch', 'cast',
-           'retain_meta', 'default_set_meta', 'retain_type', 'retain_types', 'explode_types']
+__all__ = ['type_hints', 'anno_ret', 'lenient_issubclass', 'sorted_topologically', 'TypeDispatch', 'DispatchReg',
+           'typedispatch', 'cast', 'retain_meta', 'default_set_meta', 'retain_type', 'retain_types', 'explode_types']
 
 # Cell
 from .imports import *
@@ -23,8 +23,9 @@ def anno_ret(func):
     return ann.get('return')
 
 # Cell
-def _lenient_issubclass(cls, types):
+def lenient_issubclass(cls, types):
     "If possible return whether `cls` is a subclass of `types`, otherwise return False."
+    if cls is object and types is type: return False # treat `object` as higher level than `type`
     try: return isinstance(cls, types) or issubclass(cls, types)
     except: return False
 
@@ -61,7 +62,7 @@ class _TypeDict:
     def __init__(self): self.d,self.cache = {},{}
 
     def _reset(self):
-        self.d = {k:self.d[k] for k in sorted_topologically(self.d, cmp=_lenient_issubclass)}
+        self.d = {k:self.d[k] for k in sorted_topologically(self.d, cmp=lenient_issubclass)}
         self.cache = {}
 
     def add(self, t, f):
@@ -73,7 +74,7 @@ def add(self, t, f):
     def all_matches(self, k):
         "Find first matching type that is a super-class of `k`"
         if k not in self.cache:
-            types = [f for f in self.d if k==f or (isinstance(k,type) and issubclass(k,f))]
+            types = [f for f in self.d if lenient_issubclass(k,f)]
             self.cache[k] = [self.d[o] for o in types]
         return self.cache[k]
 

nbs/03_dispatch.ipynb

@@ -201,8 +201,9 @@
    "outputs": [],
    "source": [
     "#export\n",
-    "def _lenient_issubclass(cls, types):\n",
+    "def lenient_issubclass(cls, types):\n",
     "    \"If possible return whether `cls` is a subclass of `types`, otherwise return False.\"\n",
+    "    if cls is object and types is type: return False # treat `object` as higher level than `type`\n",
     "    try: return isinstance(cls, types) or issubclass(cls, types)\n",
     "    except: return False"
    ]
@@ -213,7 +214,7 @@
    "metadata": {},
    "outputs": [],
    "source": [
-    "# depict the need for _lenient_issubclass:\n",
+    "# depict the need for lenient_issubclass:\n",
     "t = lambda: issubclass(typing.Collection, object)\n",
     "test_fail(t, contains='issubclass() arg 1 must be a class')"
    ]
@@ -224,11 +225,11 @@
    "metadata": {},
    "outputs": [],
    "source": [
-    "assert not _lenient_issubclass(typing.Collection, list)\n",
-    "assert _lenient_issubclass(list, typing.Collection)\n",
-    "assert _lenient_issubclass(typing.Collection, object)\n",
-    "assert _lenient_issubclass(typing.List, typing.Collection)\n",
-    "assert not _lenient_issubclass(typing.Collection, typing.List)"
+    "assert not lenient_issubclass(typing.Collection, list)\n",
+    "assert lenient_issubclass(list, typing.Collection)\n",
+    "assert lenient_issubclass(typing.Collection, object)\n",
+    "assert lenient_issubclass(typing.List, typing.Collection)\n",
+    "assert not lenient_issubclass(typing.Collection, typing.List)"
    ]
   },
   {
@@ -265,7 +266,7 @@
    "outputs": [],
    "source": [
     "td = {int:1, numbers.Number:2, numbers.Integral:3}\n",
-    "test_eq(sorted_topologically(td, cmp=_lenient_issubclass), [int, numbers.Integral, numbers.Number])"
+    "test_eq(sorted_topologically(td, cmp=lenient_issubclass), [int, numbers.Integral, numbers.Number])"
    ]
   },
   {
@@ -275,7 +276,7 @@
    "outputs": [],
    "source": [
     "td = [numbers.Integral, tuple, list, int, dict]\n",
-    "td = sorted_topologically(td, cmp=_lenient_issubclass)\n",
+    "td = sorted_topologically(td, cmp=lenient_issubclass)\n",
     "assert td.index(int) < td.index(numbers.Integral)"
    ]
   },
@@ -406,7 +407,7 @@
     "    def __init__(self): self.d,self.cache = {},{}\n",
     "\n",
     "    def _reset(self):\n",
-    "        self.d = {k:self.d[k] for k in sorted_topologically(self.d, cmp=_lenient_issubclass)}\n",
+    "        self.d = {k:self.d[k] for k in sorted_topologically(self.d, cmp=lenient_issubclass)}\n",
     "        self.cache = {}\n",
     "\n",
     "    def add(self, t, f):\n",
@@ -418,7 +419,7 @@
     "    def all_matches(self, k):\n",
     "        \"Find first matching type that is a super-class of `k`\"\n",
     "        if k not in self.cache:\n",
-    "            types = [f for f in self.d if k==f or (isinstance(k,type) and issubclass(k,f))]\n",
+    "            types = [f for f in self.d if lenient_issubclass(k,f)]\n",
     "            self.cache[k] = [self.d[o] for o in types]\n",
     "        return self.cache[k]\n",
     "\n",
@@ -502,6 +503,31 @@
     "                 returns_none=\"Returns `None` if return type annotation is `None` or `NoneType`.\")"
    ]
   },
+  {
+   "cell_type": "code",
+   "execution_count": null,
+   "metadata": {},
+   "outputs": [
+    {
+     "data": {
+      "text/plain": [
+       "<function __main__.a(z: type)>"
+      ]
+     },
+     "execution_count": null,
+     "metadata": {},
+     "output_type": "execute_result"
+    }
+   ],
+   "source": [
+    "def a(z:type): return 'a'\n",
+    "def b(z:object): return 'b'\n",
+    "\n",
+    "t = TypeDispatch([a,b])\n",
+    "\n",
+    "t[TypeDispatch]"
+   ]
+  },
   {
    "cell_type": "markdown",
    "metadata": {},