annotate tests/test-revlog-raw.py @ 35121:66c5a8cf2868

lfs: import the Facebook git-lfs client extension

The purpose of this is the same as the built-in largefiles extension- to handle
huge files outside of the normal storage system, generally to keep the amount of
data cloned to a lower amount.  There are several benefits of implementing the
git-lfs protocol, instead of using the largefiles extension:

  - Bitbucket and Github support (and probably wider support in 3rd party
    hosting sites in general). [1][2]

  - The number of hg internals monkey patched are several orders of magnitude
    lower, so it will be easier to reason about and maintain.  Future commands
    will likely just work, without requiring various wrappers.

  - The "standin" files are only written to the filelog, not the disk.  That
    should avoid weird edge cases where the largefile and standin files get out
    of sync. [3]  It also avoids the occasional printing of the "hidden" standin
    file in various messages.

  - Filesets like size() will work, even if the file isn't present.  (It always
    says 41 bytes for largefiles, whether present or not.)

The only place that I see where largefiles comes out on top is that it works
with `hg serve` for simple sharing, without external infrastructure.  Getting
lfs-test-server working was a hassle, and took awhile to figure out.  Maybe we
can do something to make it work in the future.

Long term, I expect that this will be highly preferred over largefiles.  But if
we are to recommend this to largefile users, there are some UI issues to
bikeshed.  Until they are resolved, I've marked this experimental, and am not
putting a pointer to this in the largefiles help.  The (non exhaustive) list of
issues I've seen so far are:

  - It isn't sufficient to just enable the largefiles extension- you have to
    explicitly add a file with --large before it will pay attention to the
    configured sizes and patterns on future adds.  The justification being that
    once you use it, you're stuck with it.  I've seen people confused by this,
    and haven't liked it myself.  But it's also saved me a few times.  Should we
    do something like have a specific enabling config setting that must be set
    in the local repo config, so that enabling this extension in the user or
    system hgrc doesn't silently start storing lfs files?

  - The largefiles extension adds a repo requirement when the first largefile is
    committed, so that the extension must always be enabled in the future.  This
    extension is not doing that, and since I only enabled it locally to avoid
    infecting other repos, I got a cryptic error about missing flag processors
    when I cloned.  Is there no repo requirement due to shallow/narrow clone
    considerations (or other future advanced things)?

  - In the (small amount of) reading I've done about the git implementation, it
    seems that the files and sizes are stored in a tracked .gitattributes file.
    I think a tracked file for this would be extremely useful for consistency
    across developers, but this kind of touches on the tracked hgrc file
    proposal a few months back.

  - The git client can specify file patterns, not just sizes.

  - The largefiles extension has a cache directory in the local repo, but also a
    system wide one.  We should probably implement a system wide cache too, so
    that multiple clones don't have to refetch the files from the server.

  - Jun mentioned other missing features, like SSH authentication, gc, etc.

The code corresponds to c0492b73c7ef in hg-experimental. [4]  The only tweaks
are to load the extension in the tests with 'lfs=' instead of
'lfs=$TESTDIR/../hgext3rd/lfs', change the import in the *.py test to hgext
(from hgext3rd), add the 'testedwith' declaration, and mark it experimental for
now.  The infinite-push, p4fastimport, and remotefilelog tests were left behind.

The devel-warnings for unregistered config options are not corrected yet, nor
are the import check warnings.

[1] https://www.mercurial-scm.org/pipermail/mercurial/2017-November/050699.html
[2] https://bitbucket.org/site/master/issues/3843/largefiles-support-bb-3903
[3] https://bz.mercurial-scm.org/show_bug.cgi?id=5738
[4] https://bitbucket.org/facebook/hg-experimental

# test revlog interaction about raw data (flagprocessor)

from __future__ import absolute_import, print_function

import sys

from mercurial import (
    encoding,
    node,
    revlog,
    transaction,
    vfs,
)

# TESTTMP is optional. This makes it convenient to run without run-tests.py
tvfs = vfs.vfs(encoding.environ.get('TESTTMP', b'/tmp'))

# Enable generaldelta otherwise revlog won't use delta as expected by the test
tvfs.options = {'generaldelta': True, 'revlogv1': True}

# The test wants to control whether to use delta explicitly, based on
# "storedeltachains".
revlog.revlog._isgooddelta = lambda self, d, textlen: self.storedeltachains

def abort(msg):
    print('abort: %s' % msg)
    # Return 0 so run-tests.py could compare the output.
    sys.exit()

# Register a revlog processor for flag EXTSTORED.
#
# It simply prepends a fixed header, and replaces '1' to 'i'. So it has
# insertion and replacement, and may be interesting to test revlog's line-based
# deltas.
_extheader = b'E\n'

def readprocessor(self, rawtext):
    # True: the returned text could be used to verify hash
    text = rawtext[len(_extheader):].replace(b'i', b'1')
    return text, True

def writeprocessor(self, text):
    # False: the returned rawtext shouldn't be used to verify hash
    rawtext = _extheader + text.replace(b'1', b'i')
    return rawtext, False

def rawprocessor(self, rawtext):
    # False: do not verify hash. Only the content returned by "readprocessor"
    # can be used to verify hash.
    return False

revlog.addflagprocessor(revlog.REVIDX_EXTSTORED,
                        (readprocessor, writeprocessor, rawprocessor))

# Utilities about reading and appending revlog

def newtransaction():
    # A transaction is required to write revlogs
    report = lambda msg: None
    return transaction.transaction(report, tvfs, {'plain': tvfs}, b'journal')

def newrevlog(name=b'_testrevlog.i', recreate=False):
    if recreate:
        tvfs.tryunlink(name)
    rlog = revlog.revlog(tvfs, name)
    return rlog

def appendrev(rlog, text, tr, isext=False, isdelta=True):
    '''Append a revision. If isext is True, set the EXTSTORED flag so flag
    processor will be used (and rawtext is different from text). If isdelta is
    True, force the revision to be a delta, otherwise it's full text.
    '''
    nextrev = len(rlog)
    p1 = rlog.node(nextrev - 1)
    p2 = node.nullid
    if isext:
        flags = revlog.REVIDX_EXTSTORED
    else:
        flags = revlog.REVIDX_DEFAULT_FLAGS
    # Change storedeltachains temporarily, to override revlog's delta decision
    rlog.storedeltachains = isdelta
    try:
        rlog.addrevision(text, tr, nextrev, p1, p2, flags=flags)
        return nextrev
    except Exception as ex:
        abort('rev %d: failed to append: %s' % (nextrev, ex))
    finally:
        # Restore storedeltachains. It is always True, see revlog.__init__
        rlog.storedeltachains = True

def addgroupcopy(rlog, tr, destname=b'_destrevlog.i', optimaldelta=True):
    '''Copy revlog to destname using revlog.addgroup. Return the copied revlog.

    This emulates push or pull. They use changegroup. Changegroup requires
    repo to work. We don't have a repo, so a dummy changegroup is used.

    If optimaldelta is True, use optimized delta parent, so the destination
    revlog could probably reuse it. Otherwise it builds sub-optimal delta, and
    the destination revlog needs more work to use it.

    This exercises some revlog.addgroup (and revlog._addrevision(text=None))
    code path, which is not covered by "appendrev" alone.
    '''
    class dummychangegroup(object):
        @staticmethod
        def deltachunk(pnode):
            pnode = pnode or node.nullid
            parentrev = rlog.rev(pnode)
            r = parentrev + 1
            if r >= len(rlog):
                return {}
            if optimaldelta:
                deltaparent = parentrev
            else:
                # suboptimal deltaparent
                deltaparent = min(0, parentrev)
            return {'node': rlog.node(r), 'p1': pnode, 'p2': node.nullid,
                    'cs': rlog.node(rlog.linkrev(r)), 'flags': rlog.flags(r),
                    'deltabase': rlog.node(deltaparent),
                    'delta': rlog.revdiff(deltaparent, r)}

        def deltaiter(self):
            chain = None
            for chunkdata in iter(lambda: self.deltachunk(chain), {}):
                node = chunkdata['node']
                p1 = chunkdata['p1']
                p2 = chunkdata['p2']
                cs = chunkdata['cs']
                deltabase = chunkdata['deltabase']
                delta = chunkdata['delta']
                flags = chunkdata['flags']

                chain = node

                yield (node, p1, p2, cs, deltabase, delta, flags)

    def linkmap(lnode):
        return rlog.rev(lnode)

    dlog = newrevlog(destname, recreate=True)
    dummydeltas = dummychangegroup().deltaiter()
    dlog.addgroup(dummydeltas, linkmap, tr)
    return dlog

def lowlevelcopy(rlog, tr, destname=b'_destrevlog.i'):
    '''Like addgroupcopy, but use the low level revlog._addrevision directly.

    It exercises some code paths that are hard to reach easily otherwise.
    '''
    dlog = newrevlog(destname, recreate=True)
    for r in rlog:
        p1 = rlog.node(r - 1)
        p2 = node.nullid
        if r == 0:
            text = rlog.revision(r, raw=True)
            cachedelta = None
        else:
            # deltaparent is more interesting if it has the EXTSTORED flag.
            deltaparent = max([0] + [p for p in range(r - 2) if rlog.flags(p)])
            text = None
            cachedelta = (deltaparent, rlog.revdiff(deltaparent, r))
        flags = rlog.flags(r)
        ifh = dfh = None
        try:
            ifh = dlog.opener(dlog.indexfile, 'a+')
            if not dlog._inline:
                dfh = dlog.opener(dlog.datafile, 'a+')
            dlog._addrevision(rlog.node(r), text, tr, r, p1, p2, flags,
                              cachedelta, ifh, dfh)
        finally:
            if dfh is not None:
                dfh.close()
            if ifh is not None:
                ifh.close()
    return dlog

# Utilities to generate revisions for testing

def genbits(n):
    '''Given a number n, generate (2 ** (n * 2) + 1) numbers in range(2 ** n).
    i.e. the generated numbers have a width of n bits.

    The combination of two adjacent numbers will cover all possible cases.
    That is to say, given any x, y where both x, and y are in range(2 ** n),
    there is an x followed immediately by y in the generated sequence.
    '''
    m = 2 ** n

    # Gray Code. See https://en.wikipedia.org/wiki/Gray_code
    gray = lambda x: x ^ (x >> 1)
    reversegray = dict((gray(i), i) for i in range(m))

    # Generate (n * 2) bit gray code, yield lower n bits as X, and look for
    # the next unused gray code where higher n bits equal to X.

    # For gray codes whose higher bits are X, a[X] of them have been used.
    a = [0] * m

    # Iterate from 0.
    x = 0
    yield x
    for i in range(m * m):
        x = reversegray[x]
        y = gray(a[x] + x * m) & (m - 1)
        assert a[x] < m
        a[x] += 1
        x = y
        yield x

def gentext(rev):
    '''Given a revision number, generate dummy text'''
    return b''.join(b'%d\n' % j for j in range(-1, rev % 5))

def writecases(rlog, tr):
    '''Write some revisions interested to the test.

    The test is interested in 3 properties of a revision:

        - Is it a delta or a full text? (isdelta)
          This is to catch some delta application issues.
        - Does it have a flag of EXTSTORED? (isext)
          This is to catch some flag processor issues. Especially when
          interacted with revlog deltas.
        - Is its text empty? (isempty)
          This is less important. It is intended to try to catch some careless
          checks like "if text" instead of "if text is None". Note: if flag
          processor is involved, raw text may be not empty.

    Write 65 revisions. So that all combinations of the above flags for
    adjacent revisions are covered. That is to say,

        len(set(
            (r.delta, r.ext, r.empty, (r+1).delta, (r+1).ext, (r+1).empty)
            for r in range(len(rlog) - 1)
           )) is 64.

    Where "r.delta", "r.ext", and "r.empty" are booleans matching properties
    mentioned above.

    Return expected [(text, rawtext)].
    '''
    result = []
    for i, x in enumerate(genbits(3)):
        isdelta, isext, isempty = bool(x & 1), bool(x & 2), bool(x & 4)
        if isempty:
            text = b''
        else:
            text = gentext(i)
        rev = appendrev(rlog, text, tr, isext=isext, isdelta=isdelta)

        # Verify text, rawtext, and rawsize
        if isext:
            rawtext = writeprocessor(None, text)[0]
        else:
            rawtext = text
        if rlog.rawsize(rev) != len(rawtext):
            abort('rev %d: wrong rawsize' % rev)
        if rlog.revision(rev, raw=False) != text:
            abort('rev %d: wrong text' % rev)
        if rlog.revision(rev, raw=True) != rawtext:
            abort('rev %d: wrong rawtext' % rev)
        result.append((text, rawtext))

        # Verify flags like isdelta, isext work as expected
        if bool(rlog.deltaparent(rev) > -1) != isdelta:
            abort('rev %d: isdelta is ineffective' % rev)
        if bool(rlog.flags(rev)) != isext:
            abort('rev %d: isext is ineffective' % rev)
    return result

# Main test and checking

def checkrevlog(rlog, expected):
    '''Check if revlog has expected contents. expected is [(text, rawtext)]'''
    # Test using different access orders. This could expose some issues
    # depending on revlog caching (see revlog._cache).
    for r0 in range(len(rlog) - 1):
        r1 = r0 + 1
        for revorder in [[r0, r1], [r1, r0]]:
            for raworder in [[True], [False], [True, False], [False, True]]:
                nlog = newrevlog()
                for rev in revorder:
                    for raw in raworder:
                        t = nlog.revision(rev, raw=raw)
                        if t != expected[rev][int(raw)]:
                            abort('rev %d: corrupted %stext'
                                  % (rev, raw and 'raw' or ''))

def maintest():
    expected = rl = None
    with newtransaction() as tr:
        rl = newrevlog(recreate=True)
        expected = writecases(rl, tr)
        checkrevlog(rl, expected)
        print('local test passed')
        # Copy via revlog.addgroup
        rl1 = addgroupcopy(rl, tr)
        checkrevlog(rl1, expected)
        rl2 = addgroupcopy(rl, tr, optimaldelta=False)
        checkrevlog(rl2, expected)
        print('addgroupcopy test passed')
        # Copy via revlog.clone
        rl3 = newrevlog(name='_destrevlog3.i', recreate=True)
        rl.clone(tr, rl3)
        checkrevlog(rl3, expected)
        print('clone test passed')
        # Copy via low-level revlog._addrevision
        rl4 = lowlevelcopy(rl, tr)
        checkrevlog(rl4, expected)
        print('lowlevelcopy test passed')

try:
    maintest()
except Exception as ex:
    abort('crashed: %s' % ex)