From: Inada Naoki <songofacandy@gmail.com>
Date: Tue, 2 Apr 2019 09:08:46 +0000 (+0900)
Subject: bpo-35838: document optionxform must be idempotent (GH-12656)
X-Git-Tag: v3.8.0a4~273
X-Git-Url: https://granicus.if.org/sourcecode?a=commitdiff_plain;h=04694a306b8f4ab54ef5fc4ba673c26fa53b0ac1;p=python

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

diff --git a/Doc/library/configparser.rst b/Doc/library/configparser.rst
index 185b4a10ec..04b52dc7b2 100644
--- a/Doc/library/configparser.rst
+++ b/Doc/library/configparser.rst
@@ -721,6 +721,12 @@ 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