pycompat: stop setting LC_CTYPE unconditionally

Changeset a25343d16ebe aimed to align how LC_CTYPE is initialized across Python
versions. However, as Yuya Nishihara pointed out, it changes the behavior of
some str methods on Python 2.

Curses requires that LC_CTYPE is initialized correctly. Therefore LC_CTYPE is
set while curses is used and reset afterwards. It shouldn’t be a problem that
some str methods behave differently on Python 2 while curses is used. At least
it’s not a regression compared to what was done before d2227d4c9e6b.

This again breaks non-ASCII filenames passed to the Subversion bindings on
Python 2. Since it didn’t work before a25343d16ebe, it’s however not really a
regression. A separate patch will be sent.

hgext/histedit.py

@@ -1710,6 +1710,7 b' def _chistedit(ui, repo, freeargs, opts)'
         ctxs = []
         for i, r in enumerate(revs):
             ctxs.append(histeditrule(ui, repo[r], i))
+        with util.with_lc_ctype():
         rc = curses.wrapper(functools.partial(_chisteditmain, repo, ctxs))
         curses.echo()
         curses.endwin()

mercurial/crecord.py

@@ -569,6 +569,7 b' def chunkselector(ui, headerlist, operat'
     if util.safehasattr(signal, b'SIGTSTP'):
         origsigtstp = signal.getsignal(signal.SIGTSTP)
     try:
+        with util.with_lc_ctype():
         curses.wrapper(chunkselector.main)
         if chunkselector.initexc is not None:
             raise chunkselector.initexc

mercurial/pycompat.py

@@ -13,7 +13,6 b' from __future__ import absolute_import'
 import getopt
 import inspect
 import json
-import locale
 import os
 import shlex
 import sys
@@ -94,26 +93,6 b' def rapply(f, xs):'
     return _rapply(f, xs)
 
 
-# Passing the '' locale means that the locale should be set according to the
-# user settings (environment variables).
-# Python sometimes avoids setting the global locale settings. When interfacing
-# with C code (e.g. the curses module or the Subversion bindings), the global
-# locale settings must be initialized correctly. Python 2 does not initialize
-# the global locale settings on interpreter startup. Python 3 sometimes
-# initializes LC_CTYPE, but not consistently at least on Windows. Therefore we
-# explicitly initialize it to get consistent behavior if it's not already
-# initialized. Since CPython commit 177d921c8c03d30daa32994362023f777624b10d,
-# LC_CTYPE is always initialized. If we require Python 3.8+, we should re-check
-# if we can remove this code.
-if locale.setlocale(locale.LC_CTYPE, None) == 'C':
-    try:
-        locale.setlocale(locale.LC_CTYPE, '')
-    except locale.Error:
-        # The likely case is that the locale from the environment variables is
-        # unknown.
-        pass
-
-
 if ispy3:
     import builtins
     import codecs

mercurial/util.py

@@ -22,6 +22,7 b' import errno'
 import gc
 import hashlib
 import itertools
+import locale
 import mmap
 import os
 import platform as pyplatform
@@ -3596,3 +3597,32 b' def uvarintdecodestream(fh):'
         if not (byte & 0x80):
             return result
         shift += 7
+
+
+# Passing the '' locale means that the locale should be set according to the
+# user settings (environment variables).
+# Python sometimes avoids setting the global locale settings. When interfacing
+# with C code (e.g. the curses module or the Subversion bindings), the global
+# locale settings must be initialized correctly. Python 2 does not initialize
+# the global locale settings on interpreter startup. Python 3 sometimes
+# initializes LC_CTYPE, but not consistently at least on Windows. Therefore we
+# explicitly initialize it to get consistent behavior if it's not already
+# initialized. Since CPython commit 177d921c8c03d30daa32994362023f777624b10d,
+# LC_CTYPE is always initialized. If we require Python 3.8+, we should re-check
+# if we can remove this code.
[e-mail]
+def with_lc_ctype():
+    oldloc = locale.setlocale(locale.LC_CTYPE, None)
+    if oldloc == 'C':
+        try:
+            try:
+                locale.setlocale(locale.LC_CTYPE, '')
+            except locale.Error:
+                # The likely case is that the locale from the environment
+                # variables is unknown.
+                pass
+            yield
+        finally:
+            locale.setlocale(locale.LC_CTYPE, oldloc)
+    else:
+        yield