Improve debug logging efficiency (Closes #155).

As suggested by @adamchainz, use lazy computation of args/kwargs pprint
to only perform complex computation when running with debug.

2 files changed, 30 insertions, 16 deletions

diff --git a/factory/utils.py b/factory/utils.py
index 6ecf9a7..806b1ec 100644
--- a/factory/utils.py
+++ b/factory/utils.py
@@ -110,15 +110,29 @@ def _safe_repr(obj):
         return obj_repr.decode('utf-8')
 
 
-def log_pprint(args=(), kwargs=None):
-    kwargs = kwargs or {}
-    return ', '.join(
-        [_safe_repr(arg) for arg in args] +
-        [
-            '%s=%s' % (key, _safe_repr(value))
-            for key, value in kwargs.items()
-        ]
-    )
+class log_pprint(object):
+    """Helper for properly printing args / kwargs passed to an object.
+
+    Since it is only used with factory.debug(), the computation is
+    performed lazily.
+    """
+    __slots__ = ['args', 'kwargs']
+
+    def __init__(self, args=(), kwargs=None):
+        self.args = args
+        self.kwargs = kwargs or {}
+
+    def __repr__(self):
+        return repr(str(self))
+
+    def __str__(self):
+        return ', '.join(
+            [_safe_repr(arg) for arg in self.args] +
+            [
+                '%s=%s' % (key, _safe_repr(value))
+                for key, value in self.kwargs.items()
+            ]
+        )
 
 
 class ResetableIterator(object):
diff --git a/tests/test_utils.py b/tests/test_utils.py
index eed7a57..77598e1 100644
--- a/tests/test_utils.py
+++ b/tests/test_utils.py
@@ -238,33 +238,33 @@ class ImportObjectTestCase(unittest.TestCase):
 
 class LogPPrintTestCase(unittest.TestCase):
     def test_nothing(self):
-        txt = utils.log_pprint()
+        txt = str(utils.log_pprint())
         self.assertEqual('', txt)
 
     def test_only_args(self):
-        txt = utils.log_pprint((1, 2, 3))
+        txt = str(utils.log_pprint((1, 2, 3)))
         self.assertEqual('1, 2, 3', txt)
 
     def test_only_kwargs(self):
-        txt = utils.log_pprint(kwargs={'a': 1, 'b': 2})
+        txt = str(utils.log_pprint(kwargs={'a': 1, 'b': 2}))
         self.assertIn(txt, ['a=1, b=2', 'b=2, a=1'])
 
     def test_bytes_args(self):
-        txt = utils.log_pprint((b'\xe1\xe2',))
+        txt = str(utils.log_pprint((b'\xe1\xe2',)))
         expected = "b'\\xe1\\xe2'"
         if is_python2:
             expected = expected.lstrip('b')
         self.assertEqual(expected, txt)
 
     def test_text_args(self):
-        txt = utils.log_pprint(('ŧêßŧ',))
+        txt = str(utils.log_pprint(('ŧêßŧ',)))
         expected = "'ŧêßŧ'"
         if is_python2:
             expected = "u'\\u0167\\xea\\xdf\\u0167'"
         self.assertEqual(expected, txt)
 
     def test_bytes_kwargs(self):
-        txt = utils.log_pprint(kwargs={'x': b'\xe1\xe2', 'y': b'\xe2\xe1'})
+        txt = str(utils.log_pprint(kwargs={'x': b'\xe1\xe2', 'y': b'\xe2\xe1'}))
         expected1 = "x=b'\\xe1\\xe2', y=b'\\xe2\\xe1'"
         expected2 = "y=b'\\xe2\\xe1', x=b'\\xe1\\xe2'"
         if is_python2:
@@ -273,7 +273,7 @@ class LogPPrintTestCase(unittest.TestCase):
         self.assertIn(txt, (expected1, expected2))
 
     def test_text_kwargs(self):
-        txt = utils.log_pprint(kwargs={'x': 'ŧêßŧ', 'y': 'ŧßêŧ'})
+        txt = str(utils.log_pprint(kwargs={'x': 'ŧêßŧ', 'y': 'ŧßêŧ'}))
         expected1 = "x='ŧêßŧ', y='ŧßêŧ'"
         expected2 = "y='ŧßêŧ', x='ŧêßŧ'"
         if is_python2: