From: Miss Islington (bot) <31488909+miss-islington@users.noreply.github.com>
Date: Tue, 2 Apr 2019 09:29:16 +0000 (-0700)
Subject: bpo-35838: document optionxform must be idempotent (GH-12656)
X-Git-Tag: v3.7.4rc1~267
X-Git-Url: http://git.ipfire.org/gitweb.cgi?a=commitdiff_plain;h=9a838c593f6ada69a37025d7ded8ac822816a74c;p=thirdparty%2FPython%2Fcpython.git

bpo-35838: document optionxform must be idempotent (GH-12656)

(cherry picked from commit 04694a306b8f4ab54ef5fc4ba673c26fa53b0ac1)

Co-authored-by: Inada Naoki <songofacandy@gmail.com>
---

diff --git a/Doc/library/configparser.rst b/Doc/library/configparser.rst
index 95cc352010e0..68b663ff7f65 100644
--- a/Doc/library/configparser.rst
+++ b/Doc/library/configparser.rst
@@ -723,6 +723,12 @@ be overridden by subclasses or by attribute assignment.
      >>> list(custom['Section2'].keys())
      ['AnotherKey']
 
+  .. note::
+     The optionxform function transforms option names to a canonical form.
+     This should be an idempotent function: if the name is already in
+     canonical form, it should be returned unchanged.
+
+
 .. attribute:: ConfigParser.SECTCRE
 
   A compiled regular expression used to parse section headers.  The default