Merge pull request #7006 from minrk/valid_formatter

only check for formatters on instances

IPython/core/formatters.py

@@ -40,38 +40,21 b' else:'
 #-----------------------------------------------------------------------------
 
 
-def _valid_formatter(f):
-    """Return whether an object is a valid formatter
-    
-    Cases checked:
+def _safe_get_formatter_method(obj, name):
+    """Safely get a formatter method
     
-    - bound methods             OK
-    - unbound methods           NO
-    - callable with zero args   OK
+    - Classes cannot have formatter methods, only instance
+    - protect against proxy objects that claim to have everything
     """
-    if f is None:
-        return False
-    elif isinstance(f, type(str.find)):
-        # unbound methods on compiled classes have type method_descriptor
-        return False
-    elif isinstance(f, types.BuiltinFunctionType):
-        # bound methods on compiled classes have type builtin_function
-        return True
-    elif callable(f):
-        # anything that works with zero args should be okay
-        try:
-            inspect.getcallargs(f)
-        except Exception:
-            return False
-        else:
-            return True
-    return False
-
-def _safe_get_formatter_method(obj, name):
-    """Safely get a formatter method"""
+    if inspect.isclass(obj):
+        # repr methods only make sense on instances, not classes
+        return None
     method = pretty._safe_getattr(obj, name, None)
-    # formatter methods must be bound
-    if _valid_formatter(method):
+    if callable(method):
+        # obj claims to have repr method...
+        if callable(pretty._safe_getattr(obj, '_ipython_canary_method_should_not_exist_', None)):
+            # ...but don't trust proxy objects that claim to have everything
+            return None
         return method
 
 

IPython/core/tests/test_formatters.py

@@ -314,7 +314,6 b' def test_print_method_bound():'
     class MyHTML(object):
         def _repr_html_(self):
             return "hello"
-
     with capture_output() as captured:
         result = f(MyHTML)
     nt.assert_is(result, None)
@@ -325,6 +324,44 b' def test_print_method_bound():'
     nt.assert_equal(result, "hello")
     nt.assert_equal(captured.stderr, "")
 
+def test_print_method_weird():
+
+    class TextMagicHat(object):
+        def __getattr__(self, key):
+            return key
+
+    f = HTMLFormatter()
+    
+    text_hat = TextMagicHat()
+    nt.assert_equal(text_hat._repr_html_, '_repr_html_')
+    with capture_output() as captured:
+        result = f(text_hat)
+    
+    nt.assert_is(result, None)
+    nt.assert_not_in("FormatterWarning", captured.stderr)
+
+    class CallableMagicHat(object):
+        def __getattr__(self, key):
+            return lambda : key
+    
+    call_hat = CallableMagicHat()
+    with capture_output() as captured:
+        result = f(call_hat)
+    
+    nt.assert_equal(result, None)
+
+    class BadReprArgs(object):
+        def _repr_html_(self, extra, args):
+            return "html"
+    
+    bad = BadReprArgs()
+    with capture_output() as captured:
+        result = f(bad)
+    
+    nt.assert_is(result, None)
+    nt.assert_not_in("FormatterWarning", captured.stderr)
+
+
 def test_format_config():
     """config objects don't pretend to support fancy reprs with lazy attrs"""
     f = HTMLFormatter()