cborutil: implement sans I/O decoder
The vendored CBOR package decodes by calling read(n) on an object.
There are a number of disadvantages to this:
* Uses blocking I/O. If sufficient data is not available, the decoder
will hang until it is.
* No support for partial reads. If the read(n) returns less data than
requested, the decoder raises an error.
* Requires the use of a file like object. If the original data is in
say a buffer, we need to "cast" it to e.g. a BytesIO to appease the
decoder.
In addition, the vendored CBOR decoder doesn't provide flexibility
that we desire. Specifically:
* It buffers indefinite length bytestrings instead of streaming them.
* It doesn't allow limiting the set of types that can be decoded. This
property is useful when implementing a "hardened" decoder that is
less susceptible to abusive input.
* It doesn't provide sufficient "hook points" and introspection to
institute checks around behavior. These are useful for implementing
a "hardened" decoder.
This all adds up to a reasonable set of justifications for writing our
own decoder.
So, this commit implements our own CBOR decoder.
At the heart of the decoder is a function that decodes a single "item"
from a buffer. This item can be a complete simple value or a special
value, such as "start of array." Using this function, we can build a
decoder that effectively iterates over the stream of decoded items and
builds up higher-level values, such as arrays, maps, sets, and indefinite
length bytestrings. And we can do this without performing I/O in the
decoder itself.
The core of the sans I/O decoder will probably not be used directly.
Instead, it is expected that we'll build utility functions for invoking
the decoder given specific input types. This will allow extreme
flexibility in how data is delivered to the decoder.
I'm pretty happy with the state of the decoder modulo the TODO items
to track wanted features to help with a "hardened" decoder. The one
thing I could be convinced to change is the handling of semantic tags.
Since we only support a single semantic tag (sets), I thought it would
be easier to handle them inline in decodeitem(). This is simpler now.
But if we add support for other semantic tags, it will likely be easier
to move semantic tag handling outside of decodeitem(). But, properly
supporting semantic tags opens up a whole can of worms, as many
semantic tags imply new types. I'm optimistic we won't need these in
Mercurial. But who knows.
I'm also pretty happy with the test coverage. Writing comprehensive
tests for partial decoding did flush out a handful of bugs. One
general improvement to testing would be fuzz testing for partial
decoding. I may implement that later. I also anticipate switching the
wire protocol code to this new decoder will flush out any lingering
bugs.
Differential Revision: https://phab.mercurial-scm.org/D4414
$ cat << EOF > buggylocking.py
> """A small extension that tests our developer warnings
> """
>
> from mercurial import error, registrar, repair, util
>
> cmdtable = {}
> command = registrar.command(cmdtable)
>
> @command(b'buggylocking', [], '')
> def buggylocking(ui, repo):
> lo = repo.lock()
> wl = repo.wlock()
> wl.release()
> lo.release()
>
> @command(b'buggytransaction', [], '')
> def buggylocking(ui, repo):
> tr = repo.transaction(b'buggy')
> # make sure we rollback the transaction as we don't want to rely on the__del__
> tr.release()
>
> @command(b'properlocking', [], '')
> def properlocking(ui, repo):
> """check that reentrance is fine"""
> wl = repo.wlock()
> lo = repo.lock()
> tr = repo.transaction(b'proper')
> tr2 = repo.transaction(b'proper')
> lo2 = repo.lock()
> wl2 = repo.wlock()
> wl2.release()
> lo2.release()
> tr2.close()
> tr.close()
> lo.release()
> wl.release()
>
> @command(b'nowaitlocking', [], '')
> def nowaitlocking(ui, repo):
> lo = repo.lock()
> wl = repo.wlock(wait=False)
> wl.release()
> lo.release()
>
> @command(b'no-wlock-write', [], '')
> def nowlockwrite(ui, repo):
> with repo.vfs(b'branch', b'a'):
> pass
>
> @command(b'no-lock-write', [], '')
> def nolockwrite(ui, repo):
> with repo.svfs(b'fncache', b'a'):
> pass
>
> @command(b'stripintr', [], '')
> def stripintr(ui, repo):
> lo = repo.lock()
> tr = repo.transaction(b'foobar')
> try:
> repair.strip(repo.ui, repo, [repo[b'.'].node()])
> finally:
> lo.release()
> @command(b'oldanddeprecated', [], '')
> def oldanddeprecated(ui, repo):
> """test deprecation warning API"""
> def foobar(ui):
> ui.deprecwarn(b'foorbar is deprecated, go shopping', b'42.1337')
> foobar(ui)
> @command(b'nouiwarning', [], '')
> def nouiwarning(ui, repo):
> util.nouideprecwarn(b'this is a test', b'13.37')
> @command(b'programmingerror', [], '')
> def programmingerror(ui, repo):
> raise error.ProgrammingError(b'something went wrong', hint=b'try again')
> EOF
$ cat << EOF >> $HGRCPATH
> [extensions]
> buggylocking=$TESTTMP/buggylocking.py
> mock=$TESTDIR/mockblackbox.py
> blackbox=
> [devel]
> all-warnings=1
> EOF
$ hg init lock-checker
$ cd lock-checker
$ hg buggylocking
devel-warn: "wlock" acquired after "lock" at: $TESTTMP/buggylocking.py:* (buggylocking) (glob)
$ cat << EOF >> $HGRCPATH
> [devel]
> all=0
> check-locks=1
> EOF
$ hg buggylocking
devel-warn: "wlock" acquired after "lock" at: $TESTTMP/buggylocking.py:* (buggylocking) (glob)
#if no-chg
$ hg buggylocking --traceback
devel-warn: "wlock" acquired after "lock" at:
*/hg:* in <module> (glob) (?)
*/mercurial/dispatch.py:* in run (glob)
*/mercurial/dispatch.py:* in dispatch (glob)
*/mercurial/dispatch.py:* in _runcatch (glob)
*/mercurial/dispatch.py:* in _callcatch (glob)
*/mercurial/scmutil.py* in callcatch (glob)
*/mercurial/dispatch.py:* in _runcatchfunc (glob)
*/mercurial/dispatch.py:* in _dispatch (glob)
*/mercurial/dispatch.py:* in runcommand (glob)
*/mercurial/dispatch.py:* in _runcommand (glob)
*/mercurial/dispatch.py:* in <lambda> (glob)
*/mercurial/util.py:* in check (glob)
$TESTTMP/buggylocking.py:* in buggylocking (glob)
#else
$ hg buggylocking --traceback
devel-warn: "wlock" acquired after "lock" at:
*/hg:* in <module> (glob) (?)
*/mercurial/dispatch.py:* in run (glob)
*/mercurial/dispatch.py:* in dispatch (glob)
*/mercurial/dispatch.py:* in _runcatch (glob)
*/mercurial/dispatch.py:* in _callcatch (glob)
*/mercurial/scmutil.py:* in callcatch (glob)
*/mercurial/dispatch.py:* in _runcatchfunc (glob)
*/mercurial/dispatch.py:* in _dispatch (glob)
*/mercurial/dispatch.py:* in runcommand (glob)
*/mercurial/dispatch.py:* in _runcommand (glob)
*/mercurial/dispatch.py:* in <lambda> (glob)
*/mercurial/util.py:* in check (glob)
*/mercurial/commands.py:* in serve (glob)
*/mercurial/server.py:* in runservice (glob)
*/mercurial/commandserver.py:* in run (glob)
*/mercurial/commandserver.py:* in _mainloop (glob)
*/mercurial/commandserver.py:* in _runworker (glob)
*/mercurial/commandserver.py:* in _serverequest (glob)
*/mercurial/commandserver.py:* in serve (glob)
*/mercurial/commandserver.py:* in serveone (glob)
*/mercurial/chgserver.py:* in runcommand (glob)
*/mercurial/commandserver.py:* in runcommand (glob)
*/mercurial/dispatch.py:* in dispatch (glob)
*/mercurial/dispatch.py:* in _runcatch (glob)
*/mercurial/dispatch.py:* in _callcatch (glob)
*/mercurial/scmutil.py:* in callcatch (glob)
*/mercurial/dispatch.py:* in _runcatchfunc (glob)
*/mercurial/dispatch.py:* in _dispatch (glob)
*/mercurial/dispatch.py:* in runcommand (glob)
*/mercurial/dispatch.py:* in _runcommand (glob)
*/mercurial/dispatch.py:* in <lambda> (glob)
*/mercurial/util.py:* in check (glob)
$TESTTMP/buggylocking.py:* in buggylocking (glob)
#endif
$ hg properlocking
$ hg nowaitlocking
Writing without lock
$ hg no-wlock-write
devel-warn: write with no wlock: "branch" at: $TESTTMP/buggylocking.py:* (nowlockwrite) (glob)
$ hg no-lock-write
devel-warn: write with no lock: "fncache" at: $TESTTMP/buggylocking.py:* (nolockwrite) (glob)
Stripping from a transaction
$ echo a > a
$ hg add a
$ hg commit -m a
$ hg stripintr 2>&1 | egrep -v '^(\*\*| )'
Traceback (most recent call last):
*ProgrammingError: cannot strip from inside a transaction (glob)
$ hg oldanddeprecated
devel-warn: foorbar is deprecated, go shopping
(compatibility will be dropped after Mercurial-42.1337, update your code.) at: $TESTTMP/buggylocking.py:* (oldanddeprecated) (glob)
#if no-chg
$ hg oldanddeprecated --traceback
devel-warn: foorbar is deprecated, go shopping
(compatibility will be dropped after Mercurial-42.1337, update your code.) at:
*/hg:* in <module> (glob) (?)
*/mercurial/dispatch.py:* in run (glob)
*/mercurial/dispatch.py:* in dispatch (glob)
*/mercurial/dispatch.py:* in _runcatch (glob)
*/mercurial/dispatch.py:* in _callcatch (glob)
*/mercurial/scmutil.py* in callcatch (glob)
*/mercurial/dispatch.py:* in _runcatchfunc (glob)
*/mercurial/dispatch.py:* in _dispatch (glob)
*/mercurial/dispatch.py:* in runcommand (glob)
*/mercurial/dispatch.py:* in _runcommand (glob)
*/mercurial/dispatch.py:* in <lambda> (glob)
*/mercurial/util.py:* in check (glob)
$TESTTMP/buggylocking.py:* in oldanddeprecated (glob)
#else
$ hg oldanddeprecated --traceback
devel-warn: foorbar is deprecated, go shopping
(compatibility will be dropped after Mercurial-42.1337, update your code.) at:
*/hg:* in <module> (glob)
*/mercurial/dispatch.py:* in run (glob)
*/mercurial/dispatch.py:* in dispatch (glob)
*/mercurial/dispatch.py:* in _runcatch (glob)
*/mercurial/dispatch.py:* in _callcatch (glob)
*/mercurial/scmutil.py:* in callcatch (glob)
*/mercurial/dispatch.py:* in _runcatchfunc (glob)
*/mercurial/dispatch.py:* in _dispatch (glob)
*/mercurial/dispatch.py:* in runcommand (glob)
*/mercurial/dispatch.py:* in _runcommand (glob)
*/mercurial/dispatch.py:* in <lambda> (glob)
*/mercurial/util.py:* in check (glob)
*/mercurial/commands.py:* in serve (glob)
*/mercurial/server.py:* in runservice (glob)
*/mercurial/commandserver.py:* in run (glob)
*/mercurial/commandserver.py:* in _mainloop (glob)
*/mercurial/commandserver.py:* in _runworker (glob)
*/mercurial/commandserver.py:* in _serverequest (glob)
*/mercurial/commandserver.py:* in serve (glob)
*/mercurial/commandserver.py:* in serveone (glob)
*/mercurial/chgserver.py:* in runcommand (glob)
*/mercurial/commandserver.py:* in runcommand (glob)
*/mercurial/dispatch.py:* in dispatch (glob)
*/mercurial/dispatch.py:* in _runcatch (glob)
*/mercurial/dispatch.py:* in _callcatch (glob)
*/mercurial/scmutil.py:* in callcatch (glob)
*/mercurial/dispatch.py:* in _runcatchfunc (glob)
*/mercurial/dispatch.py:* in _dispatch (glob)
*/mercurial/dispatch.py:* in runcommand (glob)
*/mercurial/dispatch.py:* in _runcommand (glob)
*/mercurial/dispatch.py:* in <lambda> (glob)
*/mercurial/util.py:* in check (glob)
$TESTTMP/buggylocking.py:* in oldanddeprecated (glob)
#endif
#if no-chg
$ hg blackbox -l 7
1970/01/01 00:00:00 bob @cb9a9f314b8b07ba71012fcdbc544b5a4d82ff5b (5000)> oldanddeprecated
1970/01/01 00:00:00 bob @cb9a9f314b8b07ba71012fcdbc544b5a4d82ff5b (5000)> devel-warn: foorbar is deprecated, go shopping
(compatibility will be dropped after Mercurial-42.1337, update your code.) at: $TESTTMP/buggylocking.py:* (oldanddeprecated) (glob)
1970/01/01 00:00:00 bob @cb9a9f314b8b07ba71012fcdbc544b5a4d82ff5b (5000)> oldanddeprecated exited 0 after * seconds (glob)
1970/01/01 00:00:00 bob @cb9a9f314b8b07ba71012fcdbc544b5a4d82ff5b (5000)> oldanddeprecated --traceback
1970/01/01 00:00:00 bob @cb9a9f314b8b07ba71012fcdbc544b5a4d82ff5b (5000)> devel-warn: foorbar is deprecated, go shopping
(compatibility will be dropped after Mercurial-42.1337, update your code.) at:
*/hg:* in <module> (glob) (?)
*/mercurial/dispatch.py:* in run (glob)
*/mercurial/dispatch.py:* in dispatch (glob)
*/mercurial/dispatch.py:* in _runcatch (glob)
*/mercurial/dispatch.py:* in _callcatch (glob)
*/mercurial/scmutil.py* in callcatch (glob)
*/mercurial/dispatch.py:* in _runcatchfunc (glob)
*/mercurial/dispatch.py:* in _dispatch (glob)
*/mercurial/dispatch.py:* in runcommand (glob)
*/mercurial/dispatch.py:* in _runcommand (glob)
*/mercurial/dispatch.py:* in <lambda> (glob)
*/mercurial/util.py:* in check (glob)
$TESTTMP/buggylocking.py:* in oldanddeprecated (glob)
1970/01/01 00:00:00 bob @cb9a9f314b8b07ba71012fcdbc544b5a4d82ff5b (5000)> oldanddeprecated --traceback exited 0 after * seconds (glob)
1970/01/01 00:00:00 bob @cb9a9f314b8b07ba71012fcdbc544b5a4d82ff5b (5000)> blackbox -l 7
#else
$ hg blackbox -l 7
1970/01/01 00:00:00 bob @cb9a9f314b8b07ba71012fcdbc544b5a4d82ff5b (5000)> oldanddeprecated
1970/01/01 00:00:00 bob @cb9a9f314b8b07ba71012fcdbc544b5a4d82ff5b (5000)> devel-warn: foorbar is deprecated, go shopping
(compatibility will be dropped after Mercurial-42.1337, update your code.) at: $TESTTMP/buggylocking.py:* (oldanddeprecated) (glob)
1970/01/01 00:00:00 bob @cb9a9f314b8b07ba71012fcdbc544b5a4d82ff5b (5000)> oldanddeprecated exited 0 after * seconds (glob)
1970/01/01 00:00:00 bob @cb9a9f314b8b07ba71012fcdbc544b5a4d82ff5b (5000)> oldanddeprecated --traceback
1970/01/01 00:00:00 bob @cb9a9f314b8b07ba71012fcdbc544b5a4d82ff5b (5000)> devel-warn: foorbar is deprecated, go shopping
(compatibility will be dropped after Mercurial-42.1337, update your code.) at:
*/hg:* in <module> (glob)
*/mercurial/dispatch.py:* in run (glob)
*/mercurial/dispatch.py:* in dispatch (glob)
*/mercurial/dispatch.py:* in _runcatch (glob)
*/mercurial/dispatch.py:* in _callcatch (glob)
*/mercurial/scmutil.py:* in callcatch (glob)
*/mercurial/dispatch.py:* in _runcatchfunc (glob)
*/mercurial/dispatch.py:* in _dispatch (glob)
*/mercurial/dispatch.py:* in runcommand (glob)
*/mercurial/dispatch.py:* in _runcommand (glob)
*/mercurial/dispatch.py:* in <lambda> (glob)
*/mercurial/util.py:* in check (glob)
*/mercurial/commands.py:* in serve (glob)
*/mercurial/server.py:* in runservice (glob)
*/mercurial/commandserver.py:* in run (glob)
*/mercurial/commandserver.py:* in _mainloop (glob)
*/mercurial/commandserver.py:* in _runworker (glob)
*/mercurial/commandserver.py:* in _serverequest (glob)
*/mercurial/commandserver.py:* in serve (glob)
*/mercurial/commandserver.py:* in serveone (glob)
*/mercurial/chgserver.py:* in runcommand (glob)
*/mercurial/commandserver.py:* in runcommand (glob)
*/mercurial/dispatch.py:* in dispatch (glob)
*/mercurial/dispatch.py:* in _runcatch (glob)
*/mercurial/dispatch.py:* in _callcatch (glob)
*/mercurial/scmutil.py:* in callcatch (glob)
*/mercurial/dispatch.py:* in _runcatchfunc (glob)
*/mercurial/dispatch.py:* in _dispatch (glob)
*/mercurial/dispatch.py:* in runcommand (glob)
*/mercurial/dispatch.py:* in _runcommand (glob)
*/mercurial/dispatch.py:* in <lambda> (glob)
*/mercurial/util.py:* in check (glob)
$TESTTMP/buggylocking.py:* in oldanddeprecated (glob)
1970/01/01 00:00:00 bob @cb9a9f314b8b07ba71012fcdbc544b5a4d82ff5b (5000)> oldanddeprecated --traceback exited 0 after * seconds (glob)
1970/01/01 00:00:00 bob @cb9a9f314b8b07ba71012fcdbc544b5a4d82ff5b (5000)> blackbox -l 7
#endif
Test programming error failure:
$ hg buggytransaction 2>&1 | egrep -v '^ '
** Unknown exception encountered with possibly-broken third-party extension buggylocking
** which supports versions unknown of Mercurial.
** Please disable buggylocking and try your action again.
** If that fixes the bug please report it to the extension author.
** Python * (glob)
** Mercurial Distributed SCM (*) (glob)
** Extensions loaded: * (glob)
** ProgrammingError: transaction requires locking
Traceback (most recent call last):
*ProgrammingError: transaction requires locking (glob)
$ hg programmingerror 2>&1 | egrep -v '^ '
** Unknown exception encountered with possibly-broken third-party extension buggylocking
** which supports versions unknown of Mercurial.
** Please disable buggylocking and try your action again.
** If that fixes the bug please report it to the extension author.
** Python * (glob)
** Mercurial Distributed SCM (*) (glob)
** Extensions loaded: * (glob)
** ProgrammingError: something went wrong
** (try again)
Traceback (most recent call last):
*ProgrammingError: something went wrong (glob)
Old style deprecation warning
$ hg nouiwarning
$TESTTMP/buggylocking.py:*: DeprecationWarning: this is a test (glob)
(compatibility will be dropped after Mercurial-13.37, update your code.)
util.nouideprecwarn(b'this is a test', b'13.37')
(disabled outside of test run)
$ HGEMITWARNINGS= hg nouiwarning
Test warning on config option access and registration
$ cat << EOF > ${TESTTMP}/buggyconfig.py
> """A small extension that tests our developer warnings for config"""
>
> from mercurial import registrar, configitems
>
> cmdtable = {}
> command = registrar.command(cmdtable)
>
> configtable = {}
> configitem = registrar.configitem(configtable)
>
> configitem(b'test', b'some', default=b'foo')
> configitem(b'test', b'dynamic', default=configitems.dynamicdefault)
> configitem(b'test', b'callable', default=list)
> # overwrite a core config
> configitem(b'ui', b'quiet', default=False)
> configitem(b'ui', b'interactive', default=None)
>
> @command(b'buggyconfig')
> def cmdbuggyconfig(ui, repo):
> repo.ui.config(b'ui', b'quiet', True)
> repo.ui.config(b'ui', b'interactive', False)
> repo.ui.config(b'test', b'some', b'bar')
> repo.ui.config(b'test', b'some', b'foo')
> repo.ui.config(b'test', b'dynamic', b'some-required-default')
> repo.ui.config(b'test', b'dynamic')
> repo.ui.config(b'test', b'callable', [])
> repo.ui.config(b'test', b'callable', b'foo')
> repo.ui.config(b'test', b'unregistered')
> repo.ui.config(b'unregistered', b'unregistered')
> EOF
$ hg --config "extensions.buggyconfig=${TESTTMP}/buggyconfig.py" buggyconfig
devel-warn: extension 'buggyconfig' overwrite config item 'ui.interactive' at: */mercurial/extensions.py:* (_loadextra) (glob)
devel-warn: extension 'buggyconfig' overwrite config item 'ui.quiet' at: */mercurial/extensions.py:* (_loadextra) (glob)
devel-warn: specifying a mismatched default value for a registered config item: 'ui.quiet' 'True' at: $TESTTMP/buggyconfig.py:* (cmdbuggyconfig) (glob)
devel-warn: specifying a mismatched default value for a registered config item: 'ui.interactive' 'False' at: $TESTTMP/buggyconfig.py:* (cmdbuggyconfig) (glob)
devel-warn: specifying a mismatched default value for a registered config item: 'test.some' 'bar' at: $TESTTMP/buggyconfig.py:* (cmdbuggyconfig) (glob)
devel-warn: config item requires an explicit default value: 'test.dynamic' at: $TESTTMP/buggyconfig.py:* (cmdbuggyconfig) (glob)
devel-warn: specifying a mismatched default value for a registered config item: 'test.callable' 'foo' at: $TESTTMP/buggyconfig.py:* (cmdbuggyconfig) (glob)
devel-warn: accessing unregistered config item: 'test.unregistered' at: $TESTTMP/buggyconfig.py:* (cmdbuggyconfig) (glob)
devel-warn: accessing unregistered config item: 'unregistered.unregistered' at: $TESTTMP/buggyconfig.py:* (cmdbuggyconfig) (glob)
$ cd ..