[pypy-commit] pypy fix-float-deprecation-warning: Add deprecation warning if type of result of __float__ is float inherit class

[Evgenii Gorinov]

Author: Evgenii Gorinov <jonny-k at yandex-team.ru>
Branch: fix-float-deprecation-warning
Changeset: r94927:817e823be049
Date: 2018-07-29 14:45 +0100
http://bitbucket.org/pypy/pypy/changeset/817e823be049/

Log:	Add deprecation warning if type of result of __float__ is float
	inherit class

diff --git a/pypy/objspace/std/floatobject.py b/pypy/objspace/std/floatobject.py
--- a/pypy/objspace/std/floatobject.py
+++ b/pypy/objspace/std/floatobject.py
@@ -220,6 +220,15 @@
         if space.lookup(w_value, "__float__") is not None:
             w_obj = space.float(w_value)
             if space.is_w(w_floattype, space.w_float):
+                w_obj_type = space.type(w_obj)
+                if not space.is_w(w_obj_type, space.w_float):
+                    space.warn(space.newtext(
+                        "%s.__float__ returned non-float (type %s).  "
+                        "The ability to return an instance of a strict subclass "
+                        "of float is deprecated, and may be removed "
+                        "in a future version of Python." %
+                            (space.type(w_value).name, w_obj_type.name)),
+                        space.w_DeprecationWarning)
                 return w_obj
             value = space.float_w(w_obj)
         elif space.isinstance_w(w_value, space.w_unicode):
diff --git a/pypy/objspace/std/test/test_floatobject.py b/pypy/objspace/std/test/test_floatobject.py
--- a/pypy/objspace/std/test/test_floatobject.py
+++ b/pypy/objspace/std/test/test_floatobject.py
@@ -299,6 +299,21 @@
                 return 42.
         assert float(X()) == 42.
 
+    def test_float_conversion_deprecated_warning(self):
+        import warnings
+
+        class X(float):
+            def __float__(self):
+                return self
+        x = X(42)
+
+        with warnings.catch_warnings(record=True) as log:
+            warnings.simplefilter("always", DeprecationWarning)
+            converted_x = float(x)
+
+        assert converted_x == 42.  # sanity check
+        assert len(log) == 1
+
     def test_round(self):
         import math
         assert 1.0 == round(1.0)