gh-51511: Note that codecs.open()'s encoding parameter affects automatic conversion...

(cherry picked from commit d9407b174c81fda33e6c09a6f988c9a7cb8368af)

Co-authored-by: Stanley <46876382+slateny@users.noreply.github.com>

diff --git a/Doc/library/codecs.rst b/Doc/library/codecs.rst
index 4a665f2254f8a6138a87ae3d4f760e9aa341f39f..8225236350d22ef1dac611327a6164b7a62151e4 100644 (file)
--- a/Doc/library/codecs.rst
+++ b/Doc/library/codecs.rst
@@ -189,7 +189,8 @@ wider range of codecs when working with binary files:
 
    .. note::
 
-      Underlying encoded files are always opened in binary mode.
+      If *encoding* is not ``None``, then the
+      underlying encoded files are always opened in binary mode.
       No automatic conversion of ``'\n'`` is done on reading and writing.
       The *mode* argument may be any binary mode acceptable to the built-in
       :func:`open` function; the ``'b'`` is automatically added.

diff --git a/Lib/codecs.py b/Lib/codecs.py
index e6ad6e3a0523643fab643798d818e5e4927217d6..3b173b612101e7c635303a2129e3fe363791e2eb 100644 (file)
--- a/Lib/codecs.py
+++ b/Lib/codecs.py
@@ -878,7 +878,8 @@ def open(filename, mode='r', encoding=None, errors='strict', buffering=-1):
         codecs. Output is also codec dependent and will usually be
         Unicode as well.
 
-        Underlying encoded files are always opened in binary mode.
+        If encoding is not None, then the
+        underlying encoded files are always opened in binary mode.
         The default file mode is 'r', meaning to open the file in read mode.
 
         encoding specifies the encoding which is to be used for the

diff --git a/Lib/test/test_codecs.py b/Lib/test/test_codecs.py
index 42c600dcb00de19fff64bd240f4238e647ad4575..7cabe6a83a2a363e89045cd6de31f84114dbba5d 100644 (file)
--- a/Lib/test/test_codecs.py
+++ b/Lib/test/test_codecs.py
@@ -709,7 +709,8 @@ class UTF16Test(ReadTest, unittest.TestCase):
                                          "spamspam", self.spambe)
 
     def test_bug691291(self):
-        # Files are always opened in binary mode, even if no binary mode was
+        # If encoding is not None, then
+        # files are always opened in binary mode, even if no binary mode was
         # specified.  This means that no automatic conversion of '\n' is done
         # on reading and writing.
         s1 = 'Hello\r\nworld\r\n'