view tests/test-state-extension.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

Test extension of unfinished states support.
  $ mkdir chainify
  $ cd chainify
  $ cat >> chainify.py <<EOF
  > from mercurial import cmdutil, error, extensions, exthelper, node, scmutil, state
  > from hgext import rebase
  > 
  > eh = exthelper.exthelper()
  > 
  > extsetup = eh.finalextsetup
  > cmdtable = eh.cmdtable
  > 
  > # Rebase calls addunfinished in uisetup, so we have to call it in extsetup.
  > # Ideally there'd by an 'extensions.afteruisetup()' just like
  > # 'extensions.afterloaded()' to allow nesting multiple commands.
  > @eh.extsetup
  > def _extsetup(ui):
  >     state.addunfinished(
  >         b'chainify',
  >         b'chainify.state',
  >         continueflag=True,
  >         childopnames=[b'rebase'])
  > 
  > def _node(repo, arg):
  >     return node.hex(scmutil.revsingle(repo, arg).node())
  > 
  > @eh.command(
  >     b'chainify',
  >     [(b'r', b'revs', [], b'revs to chain', b'REV'),
  >      (b'', b'continue', False, b'continue op')],
  >     b'chainify [-r REV] +',
  >     inferrepo=True)
  > def chainify(ui, repo, **opts):
  >     """Rebases r1, r2, r3, etc. into a chain."""
  >     with repo.wlock(), repo.lock():
  >         cmdstate = state.cmdstate(repo, b'chainify.state')
  >         if opts['continue']:
  >             if not cmdstate.exists():
  >                 raise error.Abort(b'no chainify in progress')
  >         else:
  >             cmdutil.checkunfinished(repo)
  >             data = {
  >                 b'tip': _node(repo, opts['revs'][0]),
  >                 b'revs': b','.join(_node(repo, r) for r in opts['revs'][1:]),
  >             }
  >             cmdstate.save(1, data)
  > 
  >         data = cmdstate.read()
  >         while data[b'revs']:
  >             tip = data[b'tip']
  >             revs = data[b'revs'].split(b',')
  >             with state.delegating(repo, b'chainify', b'rebase'):
  >                 ui.status(b'rebasing %s onto %s\n' % (revs[0][:12], tip[:12]))
  >                 if state.ischildunfinished(repo, b'chainify', b'rebase'):
  >                     rc = state.continuechild(ui, repo, b'chainify', b'rebase')
  >                 else:
  >                     rc = rebase.rebase(ui, repo, rev=[revs[0]], dest=tip)
  >                 if rc and rc != 0:
  >                     raise error.Abort(b'rebase failed (rc: %d)' % rc)
  >             data[b'tip'] = _node(repo, b'tip')
  >             data[b'revs'] = b','.join(revs[1:])
  >             cmdstate.save(1, data)
  >         cmdstate.delete()
  >         ui.status(b'done chainifying\n')
  > EOF

  $ chainifypath=`pwd`/chainify.py
  $ echo '[extensions]' >> $HGRCPATH
  $ echo "chainify = $chainifypath" >> $HGRCPATH
  $ echo "rebase =" >> $HGRCPATH

  $ cd $TESTTMP
  $ hg init a
  $ cd a
  $ echo base > base.txt
  $ hg commit -Aqm 'base commit'
  $ echo foo > file1
  $ hg commit -Aqm 'add file'
  $ hg co -q ".^"
  $ echo bar > file2
  $ hg commit -Aqm 'add other file'
  $ hg co -q ".^"
  $ echo foo2 > file1
  $ hg commit -Aqm 'add conflicting file'
  $ hg co -q ".^"
  $ hg log --graph --template '{rev} {files}'
  o  3 file1
  |
  | o  2 file2
  |/
  | o  1 file1
  |/
  @  0 base.txt
  
  $ hg chainify -r 8430cfdf77c2 -r f8596309dff8 -r a858b338b3e9
  rebasing f8596309dff8 onto 8430cfdf77c2
  rebasing 2:f8596309dff8 "add other file"
  saved backup bundle to $TESTTMP/* (glob)
  rebasing a858b338b3e9 onto 83c722183a8e
  rebasing 2:a858b338b3e9 "add conflicting file"
  merging file1
  warning: conflicts while merging file1! (edit, then use 'hg resolve --mark')
  unresolved conflicts (see 'hg resolve', then 'hg chainify --continue')
  [240]
  $ hg status --config commands.status.verbose=True
  M file1
  ? file1.orig
  # The repository is in an unfinished *chainify* state.
  
  # Unresolved merge conflicts:
  # 
  #     file1
  # 
  # To mark files as resolved:  hg resolve --mark FILE
  
  # To continue:    hg chainify --continue
  # To abort:       hg chainify --abort
  
  $ echo foo3 > file1
  $ hg resolve --mark file1
  (no more unresolved files)
  continue: hg chainify --continue
  $ hg chainify --continue
  rebasing a858b338b3e9 onto 83c722183a8e
  rebasing 2:a858b338b3e9 "add conflicting file"
  saved backup bundle to $TESTTMP/* (glob)
  done chainifying
  $ hg log --graph --template '{rev} {files}'
  o  3 file1
  |
  o  2 file2
  |
  o  1 file1
  |
  @  0 base.txt