Mercurial > hg
view tests/test-imports-checker.t @ 46607:e9901d01d135
revlog: add a mechanism to verify expected file position before appending
If someone uses `hg debuglocks`, or some non-hg process writes to the .hg
directory without respecting the locks, or if the repo's on a networked
filesystem, it's possible for the revlog code to write out corrupted data.
The form of this corruption can vary depending on what data was written and how
that happened. We are in the "networked filesystem" case (though I've had users
also do this to themselves with the "`hg debuglocks`" scenario), and most often
see this with the changelog. What ends up happening is we produce two items
(let's call them rev1 and rev2) in the .i file that have the same linkrev,
baserev, and offset into the .d file, while the data in the .d file is appended
properly. rev2's compressed_size is accurate for rev2, but when we go to
decompress the data in the .d file, we use the offset that's recorded in the
index file, which is the same as rev1, and attempt to decompress
rev2.compressed_size bytes of rev1's data. This usually does not succeed. :)
When using inline data, this also fails, though I haven't investigated why too
closely. This shows up as a "patch decode" error. I believe what's happening
there is that we're basically ignoring the offset field, getting the data
properly, but since baserev != rev, it thinks this is a delta based on rev
(instead of a full text) and can't actually apply it as such.
For now, I'm going to make this an optional component and default it to entirely
off. I may increase the default severity of this in the future, once I've
enabled it for my users and we gain more experience with it. Luckily, most of my
users have a versioned filesystem and can roll back to before the corruption has
been written, it's just a hassle to do so and not everyone knows how (so it's a
support burden). Users on other filesystems will not have that luxury, and this
can cause them to have a corrupted repository that they are unlikely to know how
to resolve, and they'll see this as a data-loss event. Refusing to create the
corruption is a much better user experience.
This mechanism is not perfect. There may be false-negatives (racy writes that
are not detected). There should not be any false-positives (non-racy writes that
are detected as such). This is not a mechanism that makes putting a repo on a
networked filesystem "safe" or "supported", just *less* likely to cause
corruption.
Differential Revision: https://phab.mercurial-scm.org/D9952
author | Kyle Lippincott <spectral@google.com> |
---|---|
date | Wed, 03 Feb 2021 16:33:10 -0800 |
parents | 303576116ac1 |
children | 42d2b31cee0b |
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#require test-repo $ . "$TESTDIR/helpers-testrepo.sh" $ testrepohgenv $ import_checker="$TESTDIR"/../contrib/import-checker.py Run the doctests from the import checker, and make sure it's working correctly. $ TERM=dumb $ export TERM $ "$PYTHON" -m doctest $import_checker Run additional tests for the import checker $ mkdir testpackage $ touch testpackage/__init__.py $ cat > testpackage/multiple.py << EOF > from __future__ import absolute_import > import os, sys > EOF $ cat > testpackage/unsorted.py << EOF > from __future__ import absolute_import > import sys > import os > EOF $ cat > testpackage/stdafterlocal.py << EOF > from __future__ import absolute_import > from . import unsorted > import os > EOF $ cat > testpackage/requirerelative.py << EOF > from __future__ import absolute_import > import testpackage.unsorted > EOF $ cat > testpackage/importalias.py << EOF > from __future__ import absolute_import > import ui > EOF $ cat > testpackage/relativestdlib.py << EOF > from __future__ import absolute_import > from .. import os > EOF $ cat > testpackage/stdlibfrom.py << EOF > from __future__ import absolute_import > from collections import abc > EOF $ cat > testpackage/symbolimport.py << EOF > from __future__ import absolute_import > from .unsorted import foo > EOF $ cat > testpackage/latesymbolimport.py << EOF > from __future__ import absolute_import > from . import unsorted > from mercurial.node import hex > EOF $ cat > testpackage/multiplegroups.py << EOF > from __future__ import absolute_import > from . import unsorted > from . import more > EOF $ mkdir testpackage/subpackage $ cat > testpackage/subpackage/levelpriority.py << EOF > from __future__ import absolute_import > from . import foo > from .. import parent > EOF $ touch testpackage/subpackage/foo.py $ cat > testpackage/subpackage/__init__.py << EOF > from __future__ import absolute_import > from . import levelpriority # should not cause cycle > EOF $ cat > testpackage/subpackage/localimport.py << EOF > from __future__ import absolute_import > from . import foo > def bar(): > # should not cause "higher-level import should come first" > from .. import unsorted > # but other errors should be detected > from .. import more > import testpackage.subpackage.levelpriority > EOF $ cat > testpackage/importmodulefromsub.py << EOF > from __future__ import absolute_import > from .subpackage import foo # not a "direct symbol import" > EOF $ cat > testpackage/importsymbolfromsub.py << EOF > from __future__ import absolute_import > from .subpackage import foo, nonmodule > EOF $ cat > testpackage/sortedentries.py << EOF > from __future__ import absolute_import > from . import ( > foo, > bar, > ) > EOF $ cat > testpackage/importfromalias.py << EOF > from __future__ import absolute_import > from . import ui > EOF $ cat > testpackage/importfromrelative.py << EOF > from __future__ import absolute_import > from testpackage.unsorted import foo > EOF $ mkdir testpackage2 $ touch testpackage2/__init__.py $ cat > testpackage2/latesymbolimport.py << EOF > from __future__ import absolute_import > from testpackage import unsorted > from mercurial.node import hex > EOF # Shadowing a stdlib module to test "relative import of stdlib module" is # allowed if the module is also being checked $ mkdir email $ touch email/__init__.py $ touch email/errors.py $ cat > email/utils.py << EOF > from __future__ import absolute_import > from . import errors > EOF $ "$PYTHON" "$import_checker" testpackage*/*.py testpackage/subpackage/*.py \ > email/*.py testpackage/importalias.py:2: ui module must be "as" aliased to uimod testpackage/importfromalias.py:2: ui from testpackage must be "as" aliased to uimod testpackage/importfromrelative.py:2: import should be relative: testpackage.unsorted testpackage/importfromrelative.py:2: direct symbol import foo from testpackage.unsorted testpackage/importsymbolfromsub.py:2: direct symbol import nonmodule from testpackage.subpackage testpackage/latesymbolimport.py:3: symbol import follows non-symbol import: mercurial.node testpackage/multiple.py:2: multiple imported names: os, sys testpackage/multiplegroups.py:3: multiple "from . import" statements testpackage/relativestdlib.py:2: relative import of stdlib module testpackage/requirerelative.py:2: import should be relative: testpackage.unsorted testpackage/sortedentries.py:2: imports from testpackage not lexically sorted: bar < foo testpackage/stdafterlocal.py:3: stdlib import "os" follows local import: testpackage testpackage/stdlibfrom.py:2: direct symbol import abc from collections testpackage/subpackage/levelpriority.py:3: higher-level import should come first: testpackage testpackage/subpackage/localimport.py:7: multiple "from .. import" statements testpackage/subpackage/localimport.py:8: import should be relative: testpackage.subpackage.levelpriority testpackage/symbolimport.py:2: direct symbol import foo from testpackage.unsorted testpackage/unsorted.py:3: imports not lexically sorted: os < sys testpackage2/latesymbolimport.py:3: symbol import follows non-symbol import: mercurial.node [1]