view mercurial/pycompat.py @ 31793:69d8fcf20014

help: document bundle specifications

I softly formalized the concept of a "bundle specification" a while
ago when I was working on clone bundles and stream clone bundles and
wanted a more robust way to define what exactly is in a bundle file.

The concept has existed for a while. Since it is part of the clone
bundles feature and exposed to the user via the "-t" argument to
`hg bundle`, it is something we need to support for the long haul.

After the 4.1 release, I heard a few people comment that they didn't
realize you could generate zstd bundles with `hg bundle`. I'm
partially to blame for not documenting it in bundle's docstring.

Additionally, I added a hacky, experimental feature for controlling
the compression level of bundles in 76104a4899ad. As the commit
message says, I went with a quick and dirty solution out of time
constraints. Furthermore, I wanted to eventually store this
configuration in the "bundlespec" so it could be made more flexible.

Given:

a) bundlespecs are here to stay
b) we don't have great documentation over what they are, despite being
   a user-facing feature
c) the list of available compression engines and their behavior isn't
   exposed
d) we need an extensible place to modify behavior of compression
   engines

I want to move forward with formalizing bundlespecs as a user-facing
feature. This commit does that by introducing a "bundlespec" help
page. Leaning on the just-added compression engine documentation
and API, the topic also conveniently lists available compression
engines and details about them. This makes features like zstd
bundle compression more discoverable. e.g. you can now
`hg help -k zstd` and it lists the "bundlespec" topic.

# 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 xmlrpclib
else:
    import http.client as httplib
    import pickle
    import queue as _queue
    import socketserver
    import xmlrpc.client as xmlrpclib

def identity(a):
    return a

if ispy3:
    import builtins
    import functools
    import io
    import struct

    fsencode = os.fsencode
    fsdecode = os.fsdecode
    # A bytes version of os.name.
    oslinesep = os.linesep.encode('ascii')
    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
    maplist = lambda *args: list(map(*args))

    # 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
    sysstr = identity

    # 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.
    fsdecode = identity

    def getoptb(args, shortlist, namelist):
        return getopt.getopt(args, shortlist, namelist)

    strkwargs = identity
    byteskwargs = identity

    oslinesep = os.linesep
    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
    maplist = map

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 _registeralias(self, origin, attr, name):
        """Alias ``origin``.``attr`` as ``name``"""
        self._aliases[sysstr(name)] = (origin, sysstr(attr))

    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
    import urlparse
    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",
    ))
    urlreq._registeraliases(urlparse, (
        "urlparse",
        "urlunparse",
    ))
    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",
        "urlparse",
        "urlunparse",
    ))
    urlreq._registeralias(urllib.parse, "unquote_to_bytes", "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