view tests/test-bookmarks-rebase.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

  $ echo "[extensions]" >> $HGRCPATH
  $ echo "rebase=" >> $HGRCPATH

initialize repository

  $ hg init

  $ echo 'a' > a
  $ hg ci -A -m "0"
  adding a

  $ echo 'b' > b
  $ hg ci -A -m "1"
  adding b

  $ hg up 0
  0 files updated, 0 files merged, 1 files removed, 0 files unresolved
  $ echo 'c' > c
  $ hg ci -A -m "2"
  adding c
  created new head

  $ echo 'd' > d
  $ hg ci -A -m "3"
  adding d

  $ hg bookmark -r 1 one
  $ hg bookmark -r 3 two
  $ hg up -q two

bookmark list

  $ hg bookmark
     one                       1:925d80f479bb
   * two                       3:2ae46b1d99a7

rebase

  $ hg rebase -s two -d one
  rebasing 3:2ae46b1d99a7 two tip "3"
  saved backup bundle to $TESTTMP/.hg/strip-backup/2ae46b1d99a7-e6b057bc-rebase.hg

  $ hg log
  changeset:   3:42e5ed2cdcf4
  bookmark:    two
  tag:         tip
  parent:      1:925d80f479bb
  user:        test
  date:        Thu Jan 01 00:00:00 1970 +0000
  summary:     3
  
  changeset:   2:db815d6d32e6
  parent:      0:f7b1eb17ad24
  user:        test
  date:        Thu Jan 01 00:00:00 1970 +0000
  summary:     2
  
  changeset:   1:925d80f479bb
  bookmark:    one
  user:        test
  date:        Thu Jan 01 00:00:00 1970 +0000
  summary:     1
  
  changeset:   0:f7b1eb17ad24
  user:        test
  date:        Thu Jan 01 00:00:00 1970 +0000
  summary:     0
  
aborted rebase should restore active bookmark.

  $ hg up 1
  0 files updated, 0 files merged, 1 files removed, 0 files unresolved
  (leaving bookmark two)
  $ echo 'e' > d
  $ hg ci -A -m "4"
  adding d
  created new head
  $ hg bookmark three
  $ hg rebase -s three -d two
  rebasing 4:dd7c838e8362 three tip "4"
  merging d
  warning: conflicts while merging d! (edit, then use 'hg resolve --mark')
  unresolved conflicts (see 'hg resolve', then 'hg rebase --continue')
  [240]
  $ hg rebase --abort
  rebase aborted
  $ hg bookmark
     one                       1:925d80f479bb
   * three                     4:dd7c838e8362
     two                       3:42e5ed2cdcf4

after aborted rebase, restoring a bookmark that has been removed should not fail

  $ hg rebase -s three -d two
  rebasing 4:dd7c838e8362 three tip "4"
  merging d
  warning: conflicts while merging d! (edit, then use 'hg resolve --mark')
  unresolved conflicts (see 'hg resolve', then 'hg rebase --continue')
  [240]
  $ hg bookmark -d three
  $ hg rebase --abort
  rebase aborted
  $ hg bookmark
     one                       1:925d80f479bb
     two                       3:42e5ed2cdcf4