Issue #25590: Merge rlcompleter getattr change from 3.5

Lib/rlcompleter.py

@@ -159,9 +159,11 @@ class Completer:
         while True:
             for word in words:
                 if (word[:n] == attr and
-                    not (noprefix and word[:n+1] == noprefix) and
-                    hasattr(thisobject, word)):
-                    val = getattr(thisobject, word)
+                    not (noprefix and word[:n+1] == noprefix)):
+                    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)
             if matches or not noprefix:

Lib/test/test_rlcompleter.py

@@ -79,6 +79,19 @@ class TestRlcompleter(unittest.TestCase):
                          ['egg.{}('.format(x) for x in dir(str)
                           if x.startswith('s')])
 
+    def test_excessive_getattr(self):
+        # Ensure getattr() is invoked no more than once per attribute
+        class Foo:
+            calls = 0
+            @property
+            def bar(self):
+                self.calls += 1
+                return None
+        f = Foo()
+        completer = rlcompleter.Completer(dict(f=f))
+        self.assertEqual(completer.complete('f.b', 0), 'f.bar')
+        self.assertEqual(f.calls, 1)
+
     def test_complete(self):
         completer = rlcompleter.Completer()
         self.assertEqual(completer.complete('', 0), '\t')

Misc/NEWS

@@ -402,6 +402,9 @@ Core and Builtins
 Library
 -------
 
+- Issue #25590: In the Readline completer, only call getattr() once per
+  attribute.
+
 - 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.