view tests/test-update-atomic.t @ 49000:dd6b67d5c256 stable

rust: fix unsound `OwningDirstateMap`

As per the previous patch, `OwningDirstateMap` is unsound. Self-referential
structs are difficult to implement correctly in Rust since the compiler is
free to move structs around as much as it wants to. They are also very rarely
needed in practice, so the state-of-the-art on how they should be done within
the Rust rules is still a bit new.

The crate `ouroboros` is an attempt at providing a safe way (in the Rust sense)
of declaring self-referential structs. It is getting a lot attention and was
improved very quickly when soundness issues were found in the past: rather than
relying on our own (limited) review circle, we might as well use the de-facto
common crate to fix this problem. This will give us a much better chance of
finding issues should any new ones be discovered as well as the benefit of
fewer `unsafe` APIs of our own.

I was starting to think about how I would present a safe API to the old struct
but soon realized that the callback-based approach was already done in
`ouroboros`, along with a lot more care towards refusing incorrect structs.

In short: we don't return a mutable reference to the `DirstateMap` anymore, we
expect users of its API to pass a `FnOnce` that takes the map as an argument.
This allows our `OwningDirstateMap` to control the input and output lifetimes
of the code that modifies it to prevent such issues.

Changing to `ouroboros` meant changing every API with it, but it is relatively
low churn in the end. It correctly identified the example buggy modification of
`copy_map_insert` outlined in the previous patch as violating the borrow rules.

Differential Revision: https://phab.mercurial-scm.org/D12429

#require execbit unix-permissions no-chg

Checking that experimental.atomic-file works.

  $ cat > $TESTTMP/show_mode.py <<EOF
  > from __future__ import print_function
  > import os
  > import stat
  > import sys
  > ST_MODE = stat.ST_MODE
  > 
  > for file_path in sys.argv[1:]:
  >     file_stat = os.stat(file_path)
  >     octal_mode = oct(file_stat[ST_MODE] & 0o777).replace('o', '')
  >     print("%s:%s" % (file_path, octal_mode))
  > 
  > EOF

  $ hg init repo
  $ cd repo

  $ cat > .hg/showwrites.py <<EOF
  > from __future__ import print_function
  > from mercurial import pycompat
  > from mercurial.utils import stringutil
  > def uisetup(ui):
  >   from mercurial import vfs
  >   class newvfs(vfs.vfs):
  >     def __call__(self, *args, **kwargs):
  >       print(pycompat.sysstr(stringutil.pprint(
  >           ('vfs open', args, sorted(list(kwargs.items()))))))
  >       return super(newvfs, self).__call__(*args, **kwargs)
  >   vfs.vfs = newvfs
  > EOF

  $ for v in a1 a2 b1 b2 c ro; do echo $v > $v; done
  $ chmod +x b*
  $ hg commit -Aqm _

# We check that
# - the changes are actually atomic
# - that permissions are correct (all 4 cases of (executable before) * (executable after))
# - that renames work, though they should be atomic anyway
# - that it works when source files are read-only (but directories are read-write still)

  $ for v in a1 a2 b1 b2 ro; do echo changed-$v > $v; done
  $ chmod -x *1; chmod +x *2
  $ hg rename c d
  $ hg commit -qm _

Check behavior without update.atomic-file

  $ hg update -r 0 -q
  $ hg update -r 1 --config extensions.showwrites=.hg/showwrites.py 2>&1 | grep "a1'.*wb"
  ('vfs open', ('a1', 'wb'), [('atomictemp', False), ('backgroundclose', True)])

  $ "$PYTHON" $TESTTMP/show_mode.py *
  a1:0644
  a2:0755
  b1:0644
  b2:0755
  d:0644
  ro:0644

Add a second revision for the ro file so we can test update when the file is
present or not

  $ echo "ro" > ro

  $ hg commit -qm _

Check behavior without update.atomic-file first

  $ hg update -C -r 0 -q

  $ hg update -r 1
  6 files updated, 0 files merged, 1 files removed, 0 files unresolved

  $ "$PYTHON" $TESTTMP/show_mode.py *
  a1:0644
  a2:0755
  b1:0644
  b2:0755
  d:0644
  ro:0644

Manually reset the mode of the read-only file

  $ chmod a-w ro

  $ "$PYTHON" $TESTTMP/show_mode.py ro
  ro:0444

Now the file is present, try to update and check the permissions of the file

  $ hg up -r 2
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved

  $ "$PYTHON" $TESTTMP/show_mode.py ro
  ro:0644

# The file which was read-only is now writable in the default behavior

Check behavior with update.atomic-files


  $ cat >> .hg/hgrc <<EOF
  > [experimental]
  > update.atomic-file = true
  > EOF

  $ hg update -C -r 0 -q
  $ hg update -r 1 --config extensions.showwrites=.hg/showwrites.py 2>&1 | grep "a1'.*wb"
  ('vfs open', ('a1', 'wb'), [('atomictemp', True), ('backgroundclose', True)])
  $ hg st -A --rev 1
  C a1
  C a2
  C b1
  C b2
  C d
  C ro

Check the file permission after update
  $ "$PYTHON" $TESTTMP/show_mode.py *
  a1:0644
  a2:0755
  b1:0644
  b2:0755
  d:0644
  ro:0644

Manually reset the mode of the read-only file

  $ chmod a-w ro

  $ "$PYTHON" $TESTTMP/show_mode.py ro
  ro:0444

Now the file is present, try to update and check the permissions of the file

  $ hg update -r 2 --traceback
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved

  $ "$PYTHON" $TESTTMP/show_mode.py ro
  ro:0644

# The behavior is the same as without atomic update