[PATCH 1 of 3] encoding: avoid cyclic dependency around "parsers" in pure Python build

FUJIWARA Katsunori foozy at lares.dti.ne.jp
Thu Oct 16 12:34:09 CDT 2014

# HG changeset patch
# User FUJIWARA Katsunori <foozy at lares.dti.ne.jp>
# Date 1413479224 -32400
#      Fri Oct 17 02:07:04 2014 +0900
# Node ID 738137a3404922e887894da69bca6382bc672e44
# Parent  da2758c0aca04fe20fef2797f80c6079099afca5
encoding: avoid cyclic dependency around "parsers" in pure Python build

80f2b63dd83a brought "asciilower" and "import parsers" into

This works fine with "parsers" module in C implementation, but doesn't
with one in pure Python implementation, because the latter causes
cyclic dependency below and aborting execution:

    util => i18n => encoding => parsers => util

This patch delays importing "parsers" module until it is really
needed, to avoid cyclic dependency around "parsers" in pure Python

diff --git a/mercurial/encoding.py b/mercurial/encoding.py
--- a/mercurial/encoding.py
+++ b/mercurial/encoding.py
@@ -5,7 +5,7 @@
 # This software may be used and distributed according to the terms of the
 # GNU General Public License version 2 or any later version.
-import error, parsers
+import error
 import unicodedata, locale, os
 def _getpreferredencoding():
@@ -258,14 +258,21 @@
             return concat(usub.encode(encoding))
     return ellipsis # no enough room for multi-column characters
-def asciilower(s):
+def _asciilower(s):
     '''convert a string to lowercase if ASCII
     Raises UnicodeDecodeError if non-ASCII characters are found.'''
     return s.lower()
-asciilower = getattr(parsers, 'asciilower', asciilower)
+def asciilower(s):
+    # delay importing avoids cyclic dependency around "parsers" in
+    # pure Python build (util => i18n => encoding => parsers => util)
+    import parsers
+    impl = getattr(parsers, 'asciilower', _asciilower)
+    global asciilower
+    asciilower = impl
+    return impl(s)
 def lower(s):
     "best-effort encoding-aware case-folding of local string s"

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