Issue #25590: Complete attribute names even if they are not yet created

Doc/whatsnew/3.6.rst

@@ -120,6 +120,10 @@ Private and special attribute names now are omitted unless the prefix starts
 with underscores.  A space or a colon can be added after completed keyword.
 (Contributed by Serhiy Storchaka in :issue:`25011` and :issue:`25209`.)
 
+Names of most attributes listed by :func:`dir` are now completed.
+Previously, names of properties and slots which were not yet created on
+an instance were excluded.  (Contributed by Martin Panter in :issue:`25590`.)
+
 
 urllib.robotparser
 ------------------

Lib/rlcompleter.py

@@ -160,12 +160,14 @@ class Completer:
             for word in words:
                 if (word[:n] == attr and
                     not (noprefix and word[:n+1] == noprefix)):
+                    match = "%s.%s" % (expr, word)
                     try:
                         val = getattr(thisobject, word)
                     except Exception:
-                        continue  # Exclude properties that are not set
-                    word = self._callable_postfix(val, "%s.%s" % (expr, word))
-                    matches.append(word)
+                        pass  # Include even if attribute not set
+                    else:
+                        match = self._callable_postfix(val, match)
+                    matches.append(match)
             if matches or not noprefix:
                 break
             if noprefix == '_':

Lib/test/test_rlcompleter.py

@@ -92,6 +92,14 @@ class TestRlcompleter(unittest.TestCase):
         self.assertEqual(completer.complete('f.b', 0), 'f.bar')
         self.assertEqual(f.calls, 1)
 
+    def test_uncreated_attr(self):
+        # Attributes like properties and slots should be completed even when
+        # they haven't been created on an instance
+        class Foo:
+            __slots__ = ("bar",)
+        completer = rlcompleter.Completer(dict(f=Foo()))
+        self.assertEqual(completer.complete('f.', 0), 'f.bar')
+
     def test_complete(self):
         completer = rlcompleter.Completer()
         self.assertEqual(completer.complete('', 0), '\t')

Misc/NEWS

@@ -85,6 +85,10 @@ Core and Builtins
 Library
 -------
 
+- Issue #25590: In the Readline completer, only call getattr() once per
+  attribute.  Also complete names of attributes such as properties and slots
+  which are listed by dir() but not yet created on an instance.
+
 - Issue #25498: Fix a crash when garbage-collecting ctypes objects created
   by wrapping a memoryview.  This was a regression made in 3.5a1.  Based
   on patch by Eryksun.