branchcache: rework the `filteredhash` logic to be more generic
We now have a more flexible `key_hashes` tuple. We duplicated various logic in
the V2 and V3 version of the cache as the goal is to start changing the logic
for V3 in the next few changesets.
from ..i18n import _
from .. import error
def get_checker(ui, revlog_name=b'changelog'):
"""Get a function that checks file handle position is as expected.
This is used to ensure that files haven't been modified outside of our
knowledge (such as on a networked filesystem, if `hg debuglocks` was used,
or writes to .hg that ignored locks happened).
Due to revlogs supporting a concept of buffered, delayed, or diverted
writes, we're allowing the files to be shorter than expected (the data may
not have been written yet), but they can't be longer.
Please note that this check is not perfect; it can't detect all cases (there
may be false-negatives/false-OKs), but it should never claim there's an
issue when there isn't (false-positives/false-failures).
"""
vpos = ui.config(b'debug', b'revlog.verifyposition.' + revlog_name)
# Avoid any `fh.tell` cost if this isn't enabled.
if not vpos or vpos not in [b'log', b'warn', b'fail']:
return None
def _checker(fh, fn, expected):
if fh.tell() <= expected:
return
msg = _(b'%s: file cursor at position %d, expected %d')
# Always log if we're going to warn or fail.
ui.log(b'debug', msg + b'\n', fn, fh.tell(), expected)
if vpos == b'warn':
ui.warn((msg + b'\n') % (fn, fh.tell(), expected))
elif vpos == b'fail':
raise error.RevlogError(msg % (fn, fh.tell(), expected))
return _checker