pycompat: add bytestr wrapper which mostly acts as a Python 2 str

This allows us to handle bytes in mostly the same manner as Python 2 str,
so we can get rid of ugly s[i:i + 1] hacks:

  s = bytestr(s)
  while i < len(s):
      c = s[i]
      ...

This is the simpler version of the previous RFC patch which tried to preserve
the bytestr type if possible. New version simply drops the bytestr wrapping
so we aren't likely to pass a bytestr to a function that expects Python 3
bytes.

mercurial/pycompat.py

@@ -1,323 +1,385 b''
 # pycompat.py - portability shim for python 3
 #
 # This software may be used and distributed according to the terms of the
 # GNU General Public License version 2 or any later version.
 
 """Mercurial portability shim for python 3.
 
 This contains aliases to hide python version-specific details from the core.
 """
 
 from __future__ import absolute_import
 
 import getopt
 import os
 import shlex
 import sys
 
 ispy3 = (sys.version_info[0] >= 3)
 
 if not ispy3:
     import cPickle as pickle
     import httplib
     import Queue as _queue
     import SocketServer as socketserver
     import urlparse
     urlunquote = urlparse.unquote
     import xmlrpclib
 else:
     import http.client as httplib
     import pickle
     import queue as _queue
     import socketserver
     import urllib.parse as urlparse
     urlunquote = urlparse.unquote_to_bytes
     import xmlrpc.client as xmlrpclib
 
 if ispy3:
     import builtins
     import functools
     import io
     import struct
 
     fsencode = os.fsencode
     fsdecode = os.fsdecode
     # A bytes version of os.name.
     osname = os.name.encode('ascii')
     ospathsep = os.pathsep.encode('ascii')
     ossep = os.sep.encode('ascii')
     osaltsep = os.altsep
     if osaltsep:
         osaltsep = osaltsep.encode('ascii')
     # os.getcwd() on Python 3 returns string, but it has os.getcwdb() which
     # returns bytes.
     getcwd = os.getcwdb
     sysplatform = sys.platform.encode('ascii')
     sysexecutable = sys.executable
     if sysexecutable:
         sysexecutable = os.fsencode(sysexecutable)
     stringio = io.BytesIO
 
     # TODO: .buffer might not exist if std streams were replaced; we'll need
     # a silly wrapper to make a bytes stream backed by a unicode one.
     stdin = sys.stdin.buffer
     stdout = sys.stdout.buffer
     stderr = sys.stderr.buffer
 
     # Since Python 3 converts argv to wchar_t type by Py_DecodeLocale() on Unix,
     # we can use os.fsencode() to get back bytes argv.
     #
     # https://hg.python.org/cpython/file/v3.5.1/Programs/python.c#l55
     #
     # TODO: On Windows, the native argv is wchar_t, so we'll need a different
     # workaround to simulate the Python 2 (i.e. ANSI Win32 API) behavior.
     if getattr(sys, 'argv', None) is not None:
         sysargv = list(map(os.fsencode, sys.argv))
 
     bytechr = struct.Struct('>B').pack
 
+    class bytestr(bytes):
+        """A bytes which mostly acts as a Python 2 str
+
+        >>> bytestr(), bytestr(bytearray(b'foo')), bytestr(u'ascii'), bytestr(1)
+        (b'', b'foo', b'ascii', b'1')
+        >>> s = bytestr(b'foo')
+        >>> assert s is bytestr(s)
+
+        There's no implicit conversion from non-ascii str as its encoding is
+        unknown:
+
+        >>> bytestr(chr(0x80)) # doctest: +ELLIPSIS
+        Traceback (most recent call last):
+          ...
+        UnicodeEncodeError: ...
+
+        Comparison between bytestr and bytes should work:
+
+        >>> assert bytestr(b'foo') == b'foo'
+        >>> assert b'foo' == bytestr(b'foo')
+        >>> assert b'f' in bytestr(b'foo')
+        >>> assert bytestr(b'f') in b'foo'
+
+        Sliced elements should be bytes, not integer:
+
+        >>> s[1], s[:2]
+        (b'o', b'fo')
+        >>> list(s), list(reversed(s))
+        ([b'f', b'o', b'o'], [b'o', b'o', b'f'])
+
+        As bytestr type isn't propagated across operations, you need to cast
+        bytes to bytestr explicitly:
+
+        >>> s = bytestr(b'foo').upper()
+        >>> t = bytestr(s)
+        >>> s[0], t[0]
+        (70, b'F')
+
+        Be careful to not pass a bytestr object to a function which expects
+        bytearray-like behavior.
+
+        >>> t = bytes(t)  # cast to bytes
+        >>> assert type(t) is bytes
+        """
+
+        def __new__(cls, s=b''):
+            if isinstance(s, bytestr):
+                return s
+            if not isinstance(s, (bytes, bytearray)):
+                s = str(s).encode(u'ascii')
+            return bytes.__new__(cls, s)
+
+        def __getitem__(self, key):
+            s = bytes.__getitem__(self, key)
+            if not isinstance(s, bytes):
+                s = bytechr(s)
+            return s
+
+        def __iter__(self):
+            return iterbytestr(bytes.__iter__(self))
+
     def iterbytestr(s):
         """Iterate bytes as if it were a str object of Python 2"""
         return map(bytechr, s)
 
     def sysstr(s):
         """Return a keyword str to be passed to Python functions such as
         getattr() and str.encode()
 
         This never raises UnicodeDecodeError. Non-ascii characters are
         considered invalid and mapped to arbitrary but unique code points
         such that 'sysstr(a) != sysstr(b)' for all 'a != b'.
         """
         if isinstance(s, builtins.str):
             return s
         return s.decode(u'latin-1')
 
     def _wrapattrfunc(f):
         @functools.wraps(f)
         def w(object, name, *args):
             return f(object, sysstr(name), *args)
         return w
 
     # these wrappers are automagically imported by hgloader
     delattr = _wrapattrfunc(builtins.delattr)
     getattr = _wrapattrfunc(builtins.getattr)
     hasattr = _wrapattrfunc(builtins.hasattr)
     setattr = _wrapattrfunc(builtins.setattr)
     xrange = builtins.range
 
     def open(name, mode='r', buffering=-1):
         return builtins.open(name, sysstr(mode), buffering)
 
     # getopt.getopt() on Python 3 deals with unicodes internally so we cannot
     # pass bytes there. Passing unicodes will result in unicodes as return
     # values which we need to convert again to bytes.
     def getoptb(args, shortlist, namelist):
         args = [a.decode('latin-1') for a in args]
         shortlist = shortlist.decode('latin-1')
         namelist = [a.decode('latin-1') for a in namelist]
         opts, args = getopt.getopt(args, shortlist, namelist)
         opts = [(a[0].encode('latin-1'), a[1].encode('latin-1'))
                 for a in opts]
         args = [a.encode('latin-1') for a in args]
         return opts, args
 
     # keys of keyword arguments in Python need to be strings which are unicodes
     # Python 3. This function takes keyword arguments, convert the keys to str.
     def strkwargs(dic):
         dic = dict((k.decode('latin-1'), v) for k, v in dic.iteritems())
         return dic
 
     # keys of keyword arguments need to be unicode while passing into
     # a function. This function helps us to convert those keys back to bytes
     # again as we need to deal with bytes.
     def byteskwargs(dic):
         dic = dict((k.encode('latin-1'), v) for k, v in dic.iteritems())
         return dic
 
     # shlex.split() accepts unicodes on Python 3. This function takes bytes
     # argument, convert it into unicodes, pass into shlex.split(), convert the
     # returned value to bytes and return that.
     # TODO: handle shlex.shlex().
     def shlexsplit(s):
         ret = shlex.split(s.decode('latin-1'))
         return [a.encode('latin-1') for a in ret]
 
 else:
     import cStringIO
 
     bytechr = chr
+    bytestr = str
     iterbytestr = iter
 
     def sysstr(s):
         return s
 
     # Partial backport from os.py in Python 3, which only accepts bytes.
     # In Python 2, our paths should only ever be bytes, a unicode path
     # indicates a bug.
     def fsencode(filename):
         if isinstance(filename, str):
             return filename
         else:
             raise TypeError(
                 "expect str, not %s" % type(filename).__name__)
 
     # In Python 2, fsdecode() has a very chance to receive bytes. So it's
     # better not to touch Python 2 part as it's already working fine.
     def fsdecode(filename):
         return filename
 
     def getoptb(args, shortlist, namelist):
         return getopt.getopt(args, shortlist, namelist)
 
     def strkwargs(dic):
         return dic
 
     def byteskwargs(dic):
         return dic
 
     osname = os.name
     ospathsep = os.pathsep
     ossep = os.sep
     osaltsep = os.altsep
     stdin = sys.stdin
     stdout = sys.stdout
     stderr = sys.stderr
     if getattr(sys, 'argv', None) is not None:
         sysargv = sys.argv
     sysplatform = sys.platform
     getcwd = os.getcwd
     sysexecutable = sys.executable
     shlexsplit = shlex.split
     stringio = cStringIO.StringIO
 
 empty = _queue.Empty
 queue = _queue.Queue
 
 class _pycompatstub(object):
     def __init__(self):
         self._aliases = {}
 
     def _registeraliases(self, origin, items):
         """Add items that will be populated at the first access"""
         items = map(sysstr, items)
         self._aliases.update(
             (item.replace(sysstr('_'), sysstr('')).lower(), (origin, item))
             for item in items)
 
     def __getattr__(self, name):
         try:
             origin, item = self._aliases[name]
         except KeyError:
             raise AttributeError(name)
         self.__dict__[name] = obj = getattr(origin, item)
         return obj
 
 httpserver = _pycompatstub()
 urlreq = _pycompatstub()
 urlerr = _pycompatstub()
 if not ispy3:
     import BaseHTTPServer
     import CGIHTTPServer
     import SimpleHTTPServer
     import urllib2
     import urllib
     urlreq._registeraliases(urllib, (
         "addclosehook",
         "addinfourl",
         "ftpwrapper",
         "pathname2url",
         "quote",
         "splitattr",
         "splitpasswd",
         "splitport",
         "splituser",
         "unquote",
         "url2pathname",
         "urlencode",
     ))
     urlreq._registeraliases(urllib2, (
         "AbstractHTTPHandler",
         "BaseHandler",
         "build_opener",
         "FileHandler",
         "FTPHandler",
         "HTTPBasicAuthHandler",
         "HTTPDigestAuthHandler",
         "HTTPHandler",
         "HTTPPasswordMgrWithDefaultRealm",
         "HTTPSHandler",
         "install_opener",
         "ProxyHandler",
         "Request",
         "urlopen",
     ))
     urlerr._registeraliases(urllib2, (
         "HTTPError",
         "URLError",
     ))
     httpserver._registeraliases(BaseHTTPServer, (
         "HTTPServer",
         "BaseHTTPRequestHandler",
     ))
     httpserver._registeraliases(SimpleHTTPServer, (
         "SimpleHTTPRequestHandler",
     ))
     httpserver._registeraliases(CGIHTTPServer, (
         "CGIHTTPRequestHandler",
     ))
 
 else:
     import urllib.parse
     urlreq._registeraliases(urllib.parse, (
         "splitattr",
         "splitpasswd",
         "splitport",
         "splituser",
         "unquote",
     ))
     import urllib.request
     urlreq._registeraliases(urllib.request, (
         "AbstractHTTPHandler",
         "BaseHandler",
         "build_opener",
         "FileHandler",
         "FTPHandler",
         "ftpwrapper",
         "HTTPHandler",
         "HTTPSHandler",
         "install_opener",
         "pathname2url",
         "HTTPBasicAuthHandler",
         "HTTPDigestAuthHandler",
         "HTTPPasswordMgrWithDefaultRealm",
         "ProxyHandler",
         "Request",
         "url2pathname",
         "urlopen",
     ))
     import urllib.response
     urlreq._registeraliases(urllib.response, (
         "addclosehook",
         "addinfourl",
     ))
     import urllib.error
     urlerr._registeraliases(urllib.error, (
         "HTTPError",
         "URLError",
     ))
     import http.server
     httpserver._registeraliases(http.server, (
         "HTTPServer",
         "BaseHTTPRequestHandler",
         "SimpleHTTPRequestHandler",
         "CGIHTTPRequestHandler",
     ))
 
     # urllib.parse.quote() accepts both str and bytes, decodes bytes
     # (if necessary), and returns str. This is wonky. We provide a custom
     # implementation that only accepts bytes and emits bytes.
     def quote(s, safe=r'/'):
         s = urllib.parse.quote_from_bytes(s, safe=safe)
         return s.encode('ascii', 'strict')
 
     urlreq.quote = quote

tests/test-doctest.py

@@ -1,52 +1,53 b''
 # this is hack to make sure no escape characters are inserted into the output
 
 from __future__ import absolute_import
 
 import doctest
 import os
 import sys
 
 ispy3 = (sys.version_info[0] >= 3)
 
 if 'TERM' in os.environ:
     del os.environ['TERM']
 
 # TODO: migrate doctests to py3 and enable them on both versions
 def testmod(name, optionflags=0, testtarget=None, py2=True, py3=False):
     if not (not ispy3 and py2 or ispy3 and py3):
         return
     __import__(name)
     mod = sys.modules[name]
     if testtarget is not None:
         mod = getattr(mod, testtarget)
     doctest.testmod(mod, optionflags=optionflags)
 
 testmod('mercurial.changegroup')
 testmod('mercurial.changelog')
 testmod('mercurial.dagparser', optionflags=doctest.NORMALIZE_WHITESPACE)
 testmod('mercurial.dispatch')
 testmod('mercurial.encoding')
 testmod('mercurial.formatter')
 testmod('mercurial.hg')
 testmod('mercurial.hgweb.hgwebdir_mod')
 testmod('mercurial.match')
 testmod('mercurial.minirst')
 testmod('mercurial.patch')
 testmod('mercurial.pathutil')
 testmod('mercurial.parser')
+testmod('mercurial.pycompat', py3=True)
 testmod('mercurial.revsetlang')
 testmod('mercurial.smartset')
 testmod('mercurial.store')
 testmod('mercurial.subrepo')
 testmod('mercurial.templatefilters')
 testmod('mercurial.templater')
 testmod('mercurial.ui')
 testmod('mercurial.url')
 testmod('mercurial.util')
 testmod('mercurial.util', testtarget='platform')
 testmod('hgext.convert.convcmd')
 testmod('hgext.convert.cvsps')
 testmod('hgext.convert.filemap')
 testmod('hgext.convert.p4')
 testmod('hgext.convert.subversion')
 testmod('hgext.mq')