view contrib/hgfixes/fix_bytesmod.py @ 24992:7df090c9c9fe

localrepo: use changelog.hasnode instead of self.__contains__

Before this patch, releasing the store lock implies the actions below, when
the transaction is aborted:

  1. "commithook()" scheduled in "localrepository.commit()" is invoked
  2. "changectx.__init__()" is invoked via "self.__contains__()"
  3. specified ID is examined against "repo.dirstate.p1()"
  4. validation function is invoked in "dirstate.p1()"

In subsequent patches, "dirstate.invalidate()" invocations for
discarding changes are replaced with "dirstateguard", but discarding
changes by "dirstateguard" is executed after releasing the store lock:
resources are acquired in "wlock => dirstateguard => store lock" order,
and are released in reverse order.

This may cause that "dirstate.p1()" still refers to the changeset to be
rolled-back at (4) above: pushing multiple patches by "hg qpush" is
a typical case.

When releasing the store lock, such changesets are:

  - not contained in "repo.changelog", if it is reloaded from
    ".hg/00changelog.i", as that file was already truncated by
    "transaction.abort()"

  - still contained in it, otherwise
    (this "dirty read" problem is discussed in "Transaction Plan"
     http://mercurial.selenic.com/wiki/TransactionPlan)

Validation function shows "unknown working parent" warning in the
former case, but reloading "repo.changelog" depends on the timestamp
of ".hg/00changelog.i". This causes occasional test failures.

In the case of scheduled "commithook()", it just wants to examine
whether "node ID" of committed changeset is still valid or not. Other
examinations implied in "changectx.__init__()" are meaningless.

To avoid showing the "unknown working parent" warning irregularly, this
patch uses "changelog.hasnode()" instead of "node in self" to examine
existence of committed changeset.

"""Fixer that changes bytes % whatever to a function that actually formats
it."""

from lib2to3 import fixer_base
from lib2to3.fixer_util import is_tuple, Call, Comma, Name, touch_import

# XXX: Implementing a blacklist in 2to3 turned out to be more troublesome than
# blacklisting some modules inside the fixers. So, this is what I came with.

blacklist = ['mercurial/demandimport.py',
             'mercurial/py3kcompat.py',
             'mercurial/i18n.py',
            ]

def isnumberremainder(formatstr, data):
    try:
        if data.value.isdigit():
            return True
    except AttributeError:
        return False

class FixBytesmod(fixer_base.BaseFix):
    # XXX: There's one case (I suppose) I can't handle: when a remainder
    # operation like foo % bar is performed, I can't really know what the
    # contents of foo and bar are. I believe the best approach is to "correct"
    # the to-be-converted code and let bytesformatter handle that case in
    # runtime.
    PATTERN = '''
              term< formatstr=STRING '%' data=STRING > |
              term< formatstr=STRING '%' data=atom > |
              term< formatstr=NAME '%' data=any > |
              term< formatstr=any '%' data=any >
              '''

    def transform(self, node, results):
        for bfn in blacklist:
            if self.filename.endswith(bfn):
                return
        if not self.filename.endswith('mercurial/py3kcompat.py'):
            touch_import('mercurial', 'py3kcompat', node=node)

        formatstr = results['formatstr'].clone()
        data = results['data'].clone()
        formatstr.prefix = '' # remove spaces from start

        if isnumberremainder(formatstr, data):
            return

        # We have two possibilities:
        # 1- An identifier or name is passed, it is going to be a leaf, thus, we
        #    just need to copy its value as an argument to the formatter;
        # 2- A tuple is explicitly passed. In this case, we're gonna explode it
        # to pass to the formatter
        # TODO: Check for normal strings. They don't need to be translated

        if is_tuple(data):
            args = [formatstr, Comma().clone()] + \
                   [c.clone() for c in data.children[:]]
        else:
            args = [formatstr, Comma().clone(), data]

        call = Call(Name('bytesformatter', prefix=' '), args)
        return call