tests/test-demandimport.py

commit: improve the files field of changelog for merges

Currently, the files list of merge commits repeats all the deletions
(either actual deletions, or files that got renamed) that happened
between base and p2 of the merge. If p2 is the main branch, the list
can easily be much bigger than the change being merged.

This results in various problems worth improving:
- changelog is bigger than necessary
- `hg log directory` lists many unrelated merge commits, and `hg log
  -v -r commit` frequently fills multiple screens worth of files
- it possibly slows down adjustlinkrev, by forcing it to read more
  manifests, and that function can certainly be a bottleneck
- the server side of pulls can waste a lot of time simply opening the
  filelogs for pointless files (the constant factors for opening even
  a tiny filelog is apparently pretty bad)

So stop listing such files as described in the code.  Impacted merge
commits and their descendants get a different hash than they would
have without this. This doesn't seem problematic, except for
convert. The previous commit helped with that in the hg->hg case (but
if you do svn->hg twice from scratch, hashes can still change).

The rest of the description is numbers. I don't have much to report,
because recreating the files list of existing repositories is not
easy:
- debugupgradeformat and bundle/unbundle don't recreate the list
- export/import tends to choke quickly applying patches or on
  description that contain diffs,
- merge commits from the convert extension don't have the right files
  list for reasons orthogonal to the current commit
- replaying the merge with hg update/hg merge/hg revert --all/hg
  commit can end up failing in hg revert
- I wasn't sure that using debugsetparents + debugrebuilddirstate
  would really build the right thing

I measured commit time before and after this change, in a case with no
files filtered out, several files filtered out (no difference) and 5k
files filtered out (+1% time).

Recreating the 100 more recent merges in a private repo, the
concatenated uncompressed files lists goes from 1.12MB to
0.52MB. Excluding 3 merges that are not representative, then the size
goes from 570k to 15k.
I converted part of mozilla-central, and observed file list shrinking
quite a bit too, starting at the very first merge, 733641d9feaf, going
from 550 files to 10 files (although they have relatively few merges,
so they probably wouldn't care).

Differential Revision: https://phab.mercurial-scm.org/D6613

from __future__ import absolute_import, print_function

from mercurial import demandimport
demandimport.enable()

import os
import subprocess
import sys
import types

# Don't import pycompat because it has too many side-effects.
ispy3 = sys.version_info[0] >= 3

# Only run if demandimport is allowed
if subprocess.call(['python', '%s/hghave' % os.environ['TESTDIR'],
                    'demandimport']):
    sys.exit(80)

# We rely on assert, which gets optimized out.
if sys.flags.optimize:
    sys.exit(80)

if ispy3:
    from importlib.util import _LazyModule

    try:
        from importlib.util import _Module as moduletype
    except ImportError:
        moduletype = types.ModuleType
else:
    moduletype = types.ModuleType

if os.name != 'nt':
    try:
        import distutils.msvc9compiler
        print('distutils.msvc9compiler needs to be an immediate '
              'importerror on non-windows platforms')
        distutils.msvc9compiler
    except ImportError:
        pass

import re

rsub = re.sub
def f(obj):
    l = repr(obj)
    l = rsub("0x[0-9a-fA-F]+", "0x?", l)
    l = rsub("from '.*'", "from '?'", l)
    l = rsub("'<[a-z]*>'", "'<whatever>'", l)
    return l

demandimport.disable()
os.environ['HGDEMANDIMPORT'] = 'disable'
# this enable call should not actually enable demandimport!
demandimport.enable()
from mercurial import node

# We use assert instead of a unittest test case because having imports inside
# functions changes behavior of the demand importer.
if ispy3:
    assert not isinstance(node, _LazyModule)
else:
    assert f(node) == "<module 'mercurial.node' from '?'>", f(node)

# now enable it for real
del os.environ['HGDEMANDIMPORT']
demandimport.enable()

# Test access to special attributes through demandmod proxy
assert 'mercurial.error' not in sys.modules
from mercurial import error as errorproxy

if ispy3:
    # unsure why this isn't lazy.
    assert not isinstance(f, _LazyModule)
    assert f(errorproxy) == "<module 'mercurial.error' from '?'>", f(errorproxy)
else:
    assert f(errorproxy) == "<unloaded module 'error'>", f(errorproxy)

doc = ' '.join(errorproxy.__doc__.split()[:3])
assert doc == 'Mercurial exceptions. This', doc
assert errorproxy.__name__ == 'mercurial.error', errorproxy.__name__

# __name__ must be accessible via __dict__ so the relative imports can be
# resolved
name = errorproxy.__dict__['__name__']
assert name == 'mercurial.error', name

if ispy3:
    assert not isinstance(errorproxy, _LazyModule)
    assert f(errorproxy) == "<module 'mercurial.error' from '?'>", f(errorproxy)
else:
    assert f(errorproxy) == "<proxied module 'error'>", f(errorproxy)

import os

if ispy3:
    assert not isinstance(os, _LazyModule)
    assert f(os) == "<module 'os' from '?'>", f(os)
else:
    assert f(os) == "<unloaded module 'os'>", f(os)

assert f(os.system) == '<built-in function system>', f(os.system)
assert f(os) == "<module 'os' from '?'>", f(os)

assert 'mercurial.utils.procutil' not in sys.modules
from mercurial.utils import procutil

if ispy3:
    assert isinstance(procutil, _LazyModule)
    assert f(procutil) == "<module 'mercurial.utils.procutil' from '?'>", f(
        procutil
    )
else:
    assert f(procutil) == "<unloaded module 'procutil'>", f(procutil)

assert f(procutil.system) == '<function system at 0x?>', f(procutil.system)
assert procutil.__class__ == moduletype, procutil.__class__
assert f(procutil) == "<module 'mercurial.utils.procutil' from '?'>", f(
    procutil
)
assert f(procutil.system) == '<function system at 0x?>', f(procutil.system)

assert 'mercurial.hgweb' not in sys.modules
from mercurial import hgweb

if ispy3:
    assert not isinstance(hgweb, _LazyModule)
    assert f(hgweb) == "<module 'mercurial.hgweb' from '?'>", f(hgweb)
    assert isinstance(hgweb.hgweb_mod, _LazyModule)
    assert (
        f(hgweb.hgweb_mod) == "<module 'mercurial.hgweb.hgweb_mod' from '?'>"
    ), f(hgweb.hgweb_mod)
else:
    assert f(hgweb) == "<unloaded module 'hgweb'>", f(hgweb)
    assert f(hgweb.hgweb_mod) == "<unloaded module 'hgweb_mod'>", f(
        hgweb.hgweb_mod
    )

assert f(hgweb) == "<module 'mercurial.hgweb' from '?'>", f(hgweb)

import re as fred

if ispy3:
    assert not isinstance(fred, _LazyModule)
    assert f(fred) == "<module 're' from '?'>"
else:
    assert f(fred) == "<unloaded module 're'>", f(fred)

import re as remod

if ispy3:
    assert not isinstance(remod, _LazyModule)
    assert f(remod) == "<module 're' from '?'>"
else:
    assert f(remod) == "<unloaded module 're'>", f(remod)

import sys as re

if ispy3:
    assert not isinstance(re, _LazyModule)
    assert f(re) == "<module 'sys' (built-in)>"
else:
    assert f(re) == "<unloaded module 'sys'>", f(re)

if ispy3:
    assert not isinstance(fred, _LazyModule)
    assert f(fred) == "<module 're' from '?'>", f(fred)
else:
    assert f(fred) == "<unloaded module 're'>", f(fred)

assert f(fred.sub) == '<function sub at 0x?>', f(fred.sub)

if ispy3:
    assert not isinstance(fred, _LazyModule)
    assert f(fred) == "<module 're' from '?'>", f(fred)
else:
    assert f(fred) == "<proxied module 're'>", f(fred)

remod.escape  # use remod
assert f(remod) == "<module 're' from '?'>", f(remod)

if ispy3:
    assert not isinstance(re, _LazyModule)
    assert f(re) == "<module 'sys' (built-in)>"
    assert f(type(re.stderr)) == "<class '_io.TextIOWrapper'>", f(
        type(re.stderr)
    )
    assert f(re) == "<module 'sys' (built-in)>"
else:
    assert f(re) == "<unloaded module 'sys'>", f(re)
    assert f(re.stderr) == "<open file '<whatever>', mode 'w' at 0x?>", f(
        re.stderr
    )
    assert f(re) == "<proxied module 'sys'>", f(re)

assert 'telnetlib' not in sys.modules
import telnetlib

if ispy3:
    assert not isinstance(telnetlib, _LazyModule)
    assert f(telnetlib) == "<module 'telnetlib' from '?'>"
else:
    assert f(telnetlib) == "<unloaded module 'telnetlib'>", f(telnetlib)

try:
    from telnetlib import unknownattr

    assert False, (
        'no demandmod should be created for attribute of non-package '
        'module:\ntelnetlib.unknownattr = %s' % f(unknownattr)
    )
except ImportError as inst:
    assert rsub(r"'", '', str(inst)).startswith(
        'cannot import name unknownattr'
    )

from mercurial import util

# Unlike the import statement, __import__() function should not raise
# ImportError even if fromlist has an unknown item
# (see Python/import.c:import_module_level() and ensure_fromlist())
assert 'zipfile' not in sys.modules
zipfileimp = __import__('zipfile', globals(), locals(), ['unknownattr'])
assert f(zipfileimp) == "<module 'zipfile' from '?'>", f(zipfileimp)
assert not util.safehasattr(zipfileimp, 'unknownattr')