view tests/test-pathencode.py @ 39772:ae531f5e583c

testing: add interface unit tests for file storage

Our strategy for supporting alternate storage backends is to define
interfaces for everything then "code to the interface."

We already have interfaces for various primitives, including file
and manifest storage.

What we don't have is generic unit tests for those interfaces. Up
to this point we've been relying on high-level integration tests
(mainly in the form of existing .t tests) to test alternate storage
backends. And my experience with developing the "simple store" test
extension is that such testing is very tedious: it takes several
minutes to run all tests and when you find a failure, it is often
non-trivial to debug.

This commit starts to change that.

This commit introduces the mercurial.testing.storage module. It
contains testing code for storage. Currently, it defines some
unittest.TestCase classes for testing the file storage interfaces.
It also defines some factory functions that allow a caller to easily
spawn a custom TestCase "bound" to a specific file storage backend
implementation.

A new .py test has been added. It simply defines a callable to produce
filelog and transaction instances on demand and then "registers" the
various test classes so the filelog class can be tested with the
storage interface unit tests.

As part of writing the tests, I identified a couple of apparent
bugs in revlog.py and filelog.py! These are tracked with inline
TODO comments.

Writing the tests makes it more obvious where the storage interface
is lacking. For example, we raise either IndexError or
error.LookupError for missing revisions depending on whether we
use an integer revision or a node. Also, we raise error.RevlogError
in various places when we should be raising a storage-agnostic
error type.

The storage interfaces are currently far from perfect and there is much
work to be done to improve them. But at least with this commit we
finally have the start of unit tests that can be used to "qualify"
the behavior of a storage backend. And when implementing and debugging
new storage backends, we now have an obvious place to define new
tests and have obvious places to insert breakpoints to facilitate
debugging. This should be invaluable when implementing new storage
backends.

I added the mercurial.testing package because these interface
conformance tests are generic and need to be usable by all storage
backends. Having the code live in tests/ would make it difficult for
storage backends implemented in extensions to test their interface
conformance. First, it would require obtaining a copy of Mercurial's
storage test code in order to test. Second, it would make testing
against multiple Mercurial versions difficult, as you would need to
import N copies of the storage testing code in order to achieve test
coverage. By making the test code part of the Mercurial distribution
itself, extensions can `import mercurial.testing.*` to access and run
the test code. The test will run against whatever Mercurial version
is active.

FWIW I've always wanted to move parts of run-tests.py into the
mercurial.* package to make the testing story simpler (e.g. imagine an
`hg debugruntests` command that could invoke the test harness). While I
have no plans to do that in the near future, establishing the
mercurial.testing package does provide a natural home for that code
should someone do this in the future.

Differential Revision: https://phab.mercurial-scm.org/D4650

# This is a randomized test that generates different pathnames every
# time it is invoked, and tests the encoding of those pathnames.
#
# It uses a simple probabilistic model to generate valid pathnames
# that have proven likely to expose bugs and divergent behavior in
# different encoding implementations.

from __future__ import absolute_import, print_function

import binascii
import collections
import itertools
import math
import os
import random
import sys
import time
from mercurial import (
    pycompat,
    store,
)

try:
    xrange
except NameError:
    xrange = range

validchars = set(map(pycompat.bytechr, range(0, 256)))
alphanum = range(ord('A'), ord('Z'))

for c in (b'\0', b'/'):
    validchars.remove(c)

winreserved = (b'aux con prn nul'.split() +
               [b'com%d' % i for i in xrange(1, 10)] +
               [b'lpt%d' % i for i in xrange(1, 10)])

def casecombinations(names):
    '''Build all case-diddled combinations of names.'''

    combos = set()

    for r in names:
        for i in xrange(len(r) + 1):
            for c in itertools.combinations(xrange(len(r)), i):
                d = r
                for j in c:
                    d = b''.join((d[:j], d[j:j + 1].upper(), d[j + 1:]))
                combos.add(d)
    return sorted(combos)

def buildprobtable(fp, cmd='hg manifest tip'):
    '''Construct and print a table of probabilities for path name
    components.  The numbers are percentages.'''

    counts = collections.defaultdict(lambda: 0)
    for line in os.popen(cmd).read().splitlines():
        if line[-2:] in ('.i', '.d'):
            line = line[:-2]
        if line.startswith('data/'):
            line = line[5:]
        for c in line:
            counts[c] += 1
    for c in '\r/\n':
        counts.pop(c, None)
    t = sum(counts.itervalues()) / 100.0
    fp.write('probtable = (')
    for i, (k, v) in enumerate(sorted(counts.items(), key=lambda x: x[1],
                                      reverse=True)):
        if (i % 5) == 0:
            fp.write('\n    ')
        vt = v / t
        if vt < 0.0005:
            break
        fp.write('(%r, %.03f), ' % (k, vt))
    fp.write('\n    )\n')

# A table of character frequencies (as percentages), gleaned by
# looking at filelog names from a real-world, very large repo.

probtable = (
    (b't', 9.828), (b'e', 9.042), (b's', 8.011), (b'a', 6.801), (b'i', 6.618),
    (b'g', 5.053), (b'r', 5.030), (b'o', 4.887), (b'p', 4.363), (b'n', 4.258),
    (b'l', 3.830), (b'h', 3.693), (b'_', 3.659), (b'.', 3.377), (b'm', 3.194),
    (b'u', 2.364), (b'd', 2.296), (b'c', 2.163), (b'b', 1.739), (b'f', 1.625),
    (b'6', 0.666), (b'j', 0.610), (b'y', 0.554), (b'x', 0.487), (b'w', 0.477),
    (b'k', 0.476), (b'v', 0.473), (b'3', 0.336), (b'1', 0.335), (b'2', 0.326),
    (b'4', 0.310), (b'5', 0.305), (b'9', 0.302), (b'8', 0.300), (b'7', 0.299),
    (b'q', 0.298), (b'0', 0.250), (b'z', 0.223), (b'-', 0.118), (b'C', 0.095),
    (b'T', 0.087), (b'F', 0.085), (b'B', 0.077), (b'S', 0.076), (b'P', 0.076),
    (b'L', 0.059), (b'A', 0.058), (b'N', 0.051), (b'D', 0.049), (b'M', 0.046),
    (b'E', 0.039), (b'I', 0.035), (b'R', 0.035), (b'G', 0.028), (b'U', 0.026),
    (b'W', 0.025), (b'O', 0.017), (b'V', 0.015), (b'H', 0.013), (b'Q', 0.011),
    (b'J', 0.007), (b'K', 0.005), (b'+', 0.004), (b'X', 0.003), (b'Y', 0.001),
    )

for c, _ in probtable:
    validchars.remove(c)
validchars = list(validchars)

def pickfrom(rng, table):
    c = 0
    r = rng.random() * sum(i[1] for i in table)
    for i, p in table:
        c += p
        if c >= r:
            return i

reservedcombos = casecombinations(winreserved)

# The first component of a name following a slash.

firsttable = (
    (lambda rng: pickfrom(rng, probtable), 90),
    (lambda rng: rng.choice(validchars), 5),
    (lambda rng: rng.choice(reservedcombos), 5),
    )

# Components of a name following the first.

resttable = firsttable[:-1]

# Special suffixes.

internalsuffixcombos = casecombinations(b'.hg .i .d'.split())

# The last component of a path, before a slash or at the end of a name.

lasttable = resttable + (
    (lambda rng: b'', 95),
    (lambda rng: rng.choice(internalsuffixcombos), 5),
    )

def makepart(rng, k):
    '''Construct a part of a pathname, without slashes.'''

    p = pickfrom(rng, firsttable)(rng)
    l = len(p)
    ps = [p]
    maxl = rng.randint(1, k)
    while l < maxl:
        p = pickfrom(rng, resttable)(rng)
        l += len(p)
        ps.append(p)
    ps.append(pickfrom(rng, lasttable)(rng))
    return b''.join(ps)

def makepath(rng, j, k):
    '''Construct a complete pathname.'''

    return (b'data/' + b'/'.join(makepart(rng, k) for _ in xrange(j)) +
            rng.choice([b'.d', b'.i']))

def genpath(rng, count):
    '''Generate random pathnames with gradually increasing lengths.'''

    mink, maxk = 1, 4096
    def steps():
        for i in xrange(count):
            yield mink + int(round(math.sqrt((maxk - mink) * float(i) / count)))
    for k in steps():
        x = rng.randint(1, k)
        y = rng.randint(1, k)
        yield makepath(rng, x, y)

def runtests(rng, seed, count):
    nerrs = 0
    for p in genpath(rng, count):
        h = store._pathencode(p)    # uses C implementation, if available
        r = store._hybridencode(p, True) # reference implementation in Python
        if h != r:
            if nerrs == 0:
                print('seed:', hex(seed)[:-1], file=sys.stderr)
            print("\np: '%s'" % p.encode("string_escape"), file=sys.stderr)
            print("h: '%s'" % h.encode("string_escape"), file=sys.stderr)
            print("r: '%s'" % r.encode("string_escape"), file=sys.stderr)
            nerrs += 1
    return nerrs

def main():
    import getopt

    # Empirically observed to take about a second to run
    count = 100
    seed = None
    opts, args = getopt.getopt(sys.argv[1:], 'c:s:',
                               ['build', 'count=', 'seed='])
    for o, a in opts:
        if o in ('-c', '--count'):
            count = int(a)
        elif o in ('-s', '--seed'):
            seed = int(a, base=0) # accepts base 10 or 16 strings
        elif o == '--build':
            buildprobtable(sys.stdout,
                           'find .hg/store/data -type f && '
                           'cat .hg/store/fncache 2>/dev/null')
            sys.exit(0)

    if seed is None:
        try:
            seed = int(binascii.hexlify(os.urandom(16)), 16)
        except AttributeError:
            seed = int(time.time() * 1000)

    rng = random.Random(seed)
    if runtests(rng, seed, count):
        sys.exit(1)

if __name__ == '__main__':
    main()