Changed errors default to 'backslashreplace'.

vsajip · Jun 17, 2019 · Jun 12, 2019 · Jun 15, 2019 · Jun 15, 2019 · e2dc53ba69c8f203db97b03ce3ad5f08671e845b
commit e2dc53ba69c8f203db97b03ce3ad5f08671e845b
diff --git a/Doc/library/logging.rst b/Doc/library/logging.rst
@@ -1204,7 +1204,12 @@ functions.
    | *errors*     | If this keyword argument is specified along |
    |              | with *filename*, its value is used when the |
    |              | FileHandler is created, and thus used when  |
-   |              | opening the output file.                    |
+   |              | opening the output file. If not specified,  |
+   |              | the value 'backslashreplace' is used. Note  |
+   |              | that if ``None`` is specified, it will be   |
+   |              | passed as such to func:`open`, which means  |
+   |              | that it will be treated the same as passing |
+   |              | 'errors'.                                   |
    +--------------+---------------------------------------------+
 
    .. versionchanged:: 3.2

diff --git a/Lib/logging/__init__.py b/Lib/logging/__init__.py
@@ -1935,7 +1935,8 @@ def basicConfig(**kwargs):
               opened.
     errors    If specified together with a filename, this value is passed to the
               created FileHandler, causing it to be used when the file is
-              opened.
+              opened in text mode. If not specified, the default value is
+              `backslashreplace`.
 
     Note that you could specify a stream created using open(filename, mode)
     rather than passing the filename and mode in. However, it should be
@@ -1965,7 +1966,7 @@ def basicConfig(**kwargs):
     try:
         force = kwargs.pop('force', False)
         encoding = kwargs.pop('encoding', None)
-        errors = kwargs.pop('errors', None)
+        errors = kwargs.pop('errors', 'backslashreplace')
         if force:
             for h in root.handlers[:]:
                 root.removeHandler(h)
@@ -1984,6 +1985,8 @@ def basicConfig(**kwargs):
                 filename = kwargs.pop("filename", None)
                 mode = kwargs.pop("filemode", 'a')
                 if filename:
+                    if 'b'in mode:
+                        errors = None
                     h = FileHandler(filename, mode,
                                     encoding=encoding, errors=errors)
                 else:

diff --git a/Lib/test/test_logging.py b/Lib/test/test_logging.py
@@ -4484,6 +4484,60 @@ def test_encoding_errors(self):
             os.remove('test.log')
             self.assertEqual(data, 'The resund Bridge joins Copenhagen to Malm')
 
+    def test_encoding_errors_default(self):
+        try:
+            encoding = 'ascii'
+            logging.basicConfig(filename='test.log', encoding=encoding,
+                                format='%(message)s', level=logging.DEBUG)
+
+            self.assertEqual(len(logging.root.handlers), 1)
+            handler = logging.root.handlers[0]
+            self.assertIsInstance(handler, logging.FileHandler)
+            self.assertEqual(handler.encoding, encoding)
+            self.assertEqual(handler.errors, 'backslashreplace')
+            logging.debug('😂: ☃️: The Øresund Bridge joins Copenhagen to Malmö')
+        finally:
+            handler.close()
+            with open('test.log', encoding='utf-8') as f:
+                data = f.read().strip()
+            os.remove('test.log')
+            self.assertEqual(data, r'\U0001f602: \u2603\ufe0f: The \xd8resund '
+                                   r'Bridge joins Copenhagen to Malm\xf6')
+
+    def test_encoding_errors_none(self):
+        # Specifying None should behave as 'strict'
+        try:
+            encoding = 'ascii'
+            logging.basicConfig(filename='test.log', encoding=encoding,
+                                errors=None,
+                                format='%(message)s', level=logging.DEBUG)
+
+            self.assertEqual(len(logging.root.handlers), 1)
+            handler = logging.root.handlers[0]
+            self.assertIsInstance(handler, logging.FileHandler)
+            self.assertEqual(handler.encoding, encoding)
+            self.assertIsNone(handler.errors)
+
+            message = []
+
+            def dummy_handle_error(record):
+                _, v, _ = sys.exc_info()
+                message.append(str(v))
+
+            handler.handleError = dummy_handle_error
+            logging.debug('The Øresund Bridge joins Copenhagen to Malmö')
+            self.assertTrue(message)
+            self.assertIn("'ascii' codec can't encode "
+                          "character '\\xd8' in position 4:", message[0])
+        finally:
+            handler.close()
+            with open('test.log', encoding='utf-8') as f:
+                data = f.read().strip()
+            os.remove('test.log')
+            # didn't write anything due to the encoding error
+            self.assertEqual(data, r'')
+
+
     def _test_log(self, method, level=None):
         # logging.root has no handlers so basicConfig should be called
         called = []