view mercurial/narrowspec.py @ 37051:40206e227412

wireproto: define and implement protocol for issuing requests

The existing HTTP and SSH wire protocols suffer from a host of flaws
and shortcomings. I've been wanting to rewrite the protocol for a while
now. Supporting partial clone - which will require new wire protocol
commands and capabilities - and other advanced server functionality
will be much easier if we start from a clean slate and don't have
to be constrained by limitations of the existing wire protocol.

This commit starts to introduce a new data exchange format for
use over the wire protocol.

The new protocol is built on top of "frames," which are atomic
units of metadata + data. Frames will make it easier to implement
proxies and other mechanisms that want to inspect data without
having to maintain state. The existing frame metadata is very
minimal and it will evolve heavily. (We will eventually support
things like concurrent requests, out-of-order responses,
compression, side-channels for status updates, etc. Some of
these will require additions to the frame header.)

Another benefit of frames is that all reads are of a fixed size.
A reader works by consuming a frame header, extracting the payload
length, then reading that many bytes. No lookahead, buffering, or
memory reallocations are needed.

The new protocol attempts to be transport agnostic. I want all that's
required to use the new protocol to be a pair of unidirectional,
half-duplex pipes. (Yes, we will eventually make use of full-duplex
pipes, but that's for another commit.) Notably, when the SSH
transport switches to this new protocol, stderr will be unused.
This is by design: the lack of stderr on HTTP harms protocol
behavior there. By shoehorning everything into a pair of pipes,
we can have more consistent behavior across transports.

We currently only define the client side parts of the new protocol,
specifically the bits for requesting that a command run. This keeps
the new code and feature small and somewhat easy to review.

We add support to `hg debugwireproto` for writing frames into
HTTP request bodies. Our tests that issue commands to the new
HTTP endpoint have been updated to transmit frames. The server
bits haven't been touched to consume the frames yet. This will
occur in the next commit...

Astute readers may notice that the command name is transmitted in
both the HTTP request URL and the command request frame. This is
partially a kludge from me initially implementing the frame-based
protocol for SSH first. But it is also a feature: I intend to
eventually support issuing multiple commands per HTTP request. This
will allow us to replace the abomination that is the "batch" wire
protocol command with a protocol-level mechanism for performing
multi-dispatch. Because I want the frame-based protocol to be
as similar as possible across transports, I'd rather we (redundantly)
include the command name in the frame than differ behavior between
transports that have out-of-band routing information (like HTTP)
readily available.

Differential Revision: https://phab.mercurial-scm.org/D2851

# narrowspec.py - methods for working with a narrow view of a repository
#
# Copyright 2017 Google, Inc.
#
# This software may be used and distributed according to the terms of the
# GNU General Public License version 2 or any later version.

from __future__ import absolute_import

import errno

from .i18n import _
from . import (
    error,
    match as matchmod,
    util,
)

FILENAME = 'narrowspec'

def _parsestoredpatterns(text):
    """Parses the narrowspec format that's stored on disk."""
    patlist = None
    includepats = []
    excludepats = []
    for l in text.splitlines():
        if l == '[includes]':
            if patlist is None:
                patlist = includepats
            else:
                raise error.Abort(_('narrowspec includes section must appear '
                                    'at most once, before excludes'))
        elif l == '[excludes]':
            if patlist is not excludepats:
                patlist = excludepats
            else:
                raise error.Abort(_('narrowspec excludes section must appear '
                                    'at most once'))
        else:
            patlist.append(l)

    return set(includepats), set(excludepats)

def parseserverpatterns(text):
    """Parses the narrowspec format that's returned by the server."""
    includepats = set()
    excludepats = set()

    # We get one entry per line, in the format "<key> <value>".
    # It's OK for value to contain other spaces.
    for kp in (l.split(' ', 1) for l in text.splitlines()):
        if len(kp) != 2:
            raise error.Abort(_('Invalid narrowspec pattern line: "%s"') % kp)
        key = kp[0]
        pat = kp[1]
        if key == 'include':
            includepats.add(pat)
        elif key == 'exclude':
            excludepats.add(pat)
        else:
            raise error.Abort(_('Invalid key "%s" in server response') % key)

    return includepats, excludepats

def normalizesplitpattern(kind, pat):
    """Returns the normalized version of a pattern and kind.

    Returns a tuple with the normalized kind and normalized pattern.
    """
    pat = pat.rstrip('/')
    _validatepattern(pat)
    return kind, pat

def _numlines(s):
    """Returns the number of lines in s, including ending empty lines."""
    # We use splitlines because it is Unicode-friendly and thus Python 3
    # compatible. However, it does not count empty lines at the end, so trick
    # it by adding a character at the end.
    return len((s + 'x').splitlines())

def _validatepattern(pat):
    """Validates the pattern and aborts if it is invalid.

    Patterns are stored in the narrowspec as newline-separated
    POSIX-style bytestring paths. There's no escaping.
    """

    # We use newlines as separators in the narrowspec file, so don't allow them
    # in patterns.
    if _numlines(pat) > 1:
        raise error.Abort(_('newlines are not allowed in narrowspec paths'))

    components = pat.split('/')
    if '.' in components or '..' in components:
        raise error.Abort(_('"." and ".." are not allowed in narrowspec paths'))

def normalizepattern(pattern, defaultkind='path'):
    """Returns the normalized version of a text-format pattern.

    If the pattern has no kind, the default will be added.
    """
    kind, pat = matchmod._patsplit(pattern, defaultkind)
    return '%s:%s' % normalizesplitpattern(kind, pat)

def parsepatterns(pats):
    """Parses a list of patterns into a typed pattern set."""
    return set(normalizepattern(p) for p in pats)

def format(includes, excludes):
    output = '[includes]\n'
    for i in sorted(includes - excludes):
        output += i + '\n'
    output += '[excludes]\n'
    for e in sorted(excludes):
        output += e + '\n'
    return output

def match(root, include=None, exclude=None):
    if not include:
        # Passing empty include and empty exclude to matchmod.match()
        # gives a matcher that matches everything, so explicitly use
        # the nevermatcher.
        return matchmod.never(root, '')
    return matchmod.match(root, '', [], include=include or [],
                          exclude=exclude or [])

def needsexpansion(includes):
    return [i for i in includes if i.startswith('include:')]

def load(repo):
    try:
        spec = repo.vfs.read(FILENAME)
    except IOError as e:
        # Treat "narrowspec does not exist" the same as "narrowspec file exists
        # and is empty".
        if e.errno == errno.ENOENT:
            # Without this the next call to load will use the cached
            # non-existence of the file, which can cause some odd issues.
            repo.invalidate(clearfilecache=True)
            return set(), set()
        raise
    return _parsestoredpatterns(spec)

def save(repo, includepats, excludepats):
    spec = format(includepats, excludepats)
    repo.vfs.write(FILENAME, spec)

def restrictpatterns(req_includes, req_excludes, repo_includes, repo_excludes):
    r""" Restricts the patterns according to repo settings,
    results in a logical AND operation

    :param req_includes: requested includes
    :param req_excludes: requested excludes
    :param repo_includes: repo includes
    :param repo_excludes: repo excludes
    :return: include patterns, exclude patterns, and invalid include patterns.

    >>> restrictpatterns({'f1','f2'}, {}, ['f1'], [])
    (set(['f1']), {}, [])
    >>> restrictpatterns({'f1'}, {}, ['f1','f2'], [])
    (set(['f1']), {}, [])
    >>> restrictpatterns({'f1/fc1', 'f3/fc3'}, {}, ['f1','f2'], [])
    (set(['f1/fc1']), {}, [])
    >>> restrictpatterns({'f1_fc1'}, {}, ['f1','f2'], [])
    ([], set(['path:.']), [])
    >>> restrictpatterns({'f1/../f2/fc2'}, {}, ['f1','f2'], [])
    (set(['f2/fc2']), {}, [])
    >>> restrictpatterns({'f1/../f3/fc3'}, {}, ['f1','f2'], [])
    ([], set(['path:.']), [])
    >>> restrictpatterns({'f1/$non_exitent_var'}, {}, ['f1','f2'], [])
    (set(['f1/$non_exitent_var']), {}, [])
    """
    res_excludes = set(req_excludes)
    res_excludes.update(repo_excludes)
    invalid_includes = []
    if not req_includes:
        res_includes = set(repo_includes)
    elif 'path:.' not in repo_includes:
        res_includes = []
        for req_include in req_includes:
            req_include = util.expandpath(util.normpath(req_include))
            if req_include in repo_includes:
                res_includes.append(req_include)
                continue
            valid = False
            for repo_include in repo_includes:
                if req_include.startswith(repo_include + '/'):
                    valid = True
                    res_includes.append(req_include)
                    break
            if not valid:
                invalid_includes.append(req_include)
        if len(res_includes) == 0:
            res_excludes = {'path:.'}
        else:
            res_includes = set(res_includes)
    else:
        res_includes = set(req_includes)
    return res_includes, res_excludes, invalid_includes