view tests/test-remotefilelog-tags.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 no-windows

  $ . "$TESTDIR/remotefilelog-library.sh"

  $ hg init master
  $ cd master
  $ cat >> .hg/hgrc <<EOF
  > [remotefilelog]
  > server=True
  > EOF
  $ echo x > foo
  $ echo y > bar
  $ hg commit -qAm one
  $ hg tag tag1
  $ cd ..

# clone with tags

  $ hg clone --shallow ssh://user@dummy/master shallow --noupdate --config remotefilelog.excludepattern=.hgtags
  streaming all changes
  3 files to transfer, 662 bytes of data (no-zstd !)
  transferred 662 bytes in * seconds (* */sec) (glob) (no-zstd !)
  3 files to transfer, 665 bytes of data (zstd !)
  transferred 665 bytes in * seconds (* */sec) (glob) (zstd !)
  searching for changes
  no changes found
  $ cat >> shallow/.hg/hgrc <<EOF
  > [remotefilelog]
  > cachepath=$PWD/hgcache
  > debug=True
  > reponame = master
  > excludepattern=.hgtags
  > [extensions]
  > remotefilelog=
  > EOF

  $ cd shallow
  $ ls .hg/store/data
  ~2ehgtags.i
  $ hg tags
  tip                                1:6ce44dcfda68
  tag1                               0:e0360bc0d9e1
  $ hg update
  3 files updated, 0 files merged, 0 files removed, 0 files unresolved
  2 files fetched over 1 fetches - (2 misses, 0.00% hit ratio) over *s (glob)

# pull with tags

  $ cd ../master
  $ hg tag tag2
  $ cd ../shallow
  $ hg pull
  pulling from ssh://user@dummy/master
  searching for changes
  adding changesets
  adding manifests
  adding file changes
  added 1 changesets with 0 changes to 0 files
  new changesets 6a22dfa4fd34
  (run 'hg update' to get a working copy)
  $ hg tags
  tip                                2:6a22dfa4fd34
  tag2                               1:6ce44dcfda68
  tag1                               0:e0360bc0d9e1
  $ hg update
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved

  $ ls .hg/store/data
  ~2ehgtags.i

  $ hg log -l 1 --stat
  changeset:   2:6a22dfa4fd34
  tag:         tip
  user:        test
  date:        Thu Jan 01 00:00:00 1970 +0000
  summary:     Added tag tag2 for changeset 6ce44dcfda68
  
   .hgtags |  1 +
   1 files changed, 1 insertions(+), 0 deletions(-)