view tests/test-histedit-drop.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

  $ . "$TESTDIR/histedit-helpers.sh"

  $ cat >> $HGRCPATH <<EOF
  > [extensions]
  > histedit=
  > EOF

  $ initrepo ()
  > {
  >     hg init r
  >     cd r
  >     for x in a b c d e f ; do
  >         echo $x > $x
  >         hg add $x
  >         hg ci -m $x
  >     done
  > }

  $ initrepo

log before edit
  $ hg log --graph
  @  changeset:   5:652413bf663e
  |  tag:         tip
  |  user:        test
  |  date:        Thu Jan 01 00:00:00 1970 +0000
  |  summary:     f
  |
  o  changeset:   4:e860deea161a
  |  user:        test
  |  date:        Thu Jan 01 00:00:00 1970 +0000
  |  summary:     e
  |
  o  changeset:   3:055a42cdd887
  |  user:        test
  |  date:        Thu Jan 01 00:00:00 1970 +0000
  |  summary:     d
  |
  o  changeset:   2:177f92b77385
  |  user:        test
  |  date:        Thu Jan 01 00:00:00 1970 +0000
  |  summary:     c
  |
  o  changeset:   1:d2ae7f538514
  |  user:        test
  |  date:        Thu Jan 01 00:00:00 1970 +0000
  |  summary:     b
  |
  o  changeset:   0:cb9a9f314b8b
     user:        test
     date:        Thu Jan 01 00:00:00 1970 +0000
     summary:     a
  

edit the history
  $ hg histedit 177f92b77385 --commands - 2>&1 << EOF | fixbundle
  > drop 177f92b77385 c
  > pick e860deea161a e
  > pick 652413bf663e f
  > pick 055a42cdd887 d
  > EOF

log after edit
  $ hg log --graph
  @  changeset:   4:f518305ce889
  |  tag:         tip
  |  user:        test
  |  date:        Thu Jan 01 00:00:00 1970 +0000
  |  summary:     d
  |
  o  changeset:   3:a4f7421b80f7
  |  user:        test
  |  date:        Thu Jan 01 00:00:00 1970 +0000
  |  summary:     f
  |
  o  changeset:   2:ee283cb5f2d5
  |  user:        test
  |  date:        Thu Jan 01 00:00:00 1970 +0000
  |  summary:     e
  |
  o  changeset:   1:d2ae7f538514
  |  user:        test
  |  date:        Thu Jan 01 00:00:00 1970 +0000
  |  summary:     b
  |
  o  changeset:   0:cb9a9f314b8b
     user:        test
     date:        Thu Jan 01 00:00:00 1970 +0000
     summary:     a
  

Check histedit_source

  $ hg log --debug --rev f518305ce889
  changeset:   4:f518305ce889c07cb5bd05522176d75590ef3324
  tag:         tip
  phase:       draft
  parent:      3:a4f7421b80f79fcc59fff01bcbf4a53d127dd6d3
  parent:      -1:0000000000000000000000000000000000000000
  manifest:    4:d3d4f51c157ff242c32ff745d4799aaa26ccda44
  user:        test
  date:        Thu Jan 01 00:00:00 1970 +0000
  files+:      d
  extra:       branch=default
  extra:       histedit_source=055a42cdd88768532f9cf79daa407fc8d138de9b
  description:
  d
  
  

manifest after edit
  $ hg manifest
  a
  b
  d
  e
  f

Drop the last changeset

  $ hg histedit ee283cb5f2d5 --commands - 2>&1 << EOF | fixbundle
  > pick ee283cb5f2d5 e
  > pick a4f7421b80f7 f
  > drop f518305ce889 d
  > EOF
  $ hg log --graph
  @  changeset:   3:a4f7421b80f7
  |  tag:         tip
  |  user:        test
  |  date:        Thu Jan 01 00:00:00 1970 +0000
  |  summary:     f
  |
  o  changeset:   2:ee283cb5f2d5
  |  user:        test
  |  date:        Thu Jan 01 00:00:00 1970 +0000
  |  summary:     e
  |
  o  changeset:   1:d2ae7f538514
  |  user:        test
  |  date:        Thu Jan 01 00:00:00 1970 +0000
  |  summary:     b
  |
  o  changeset:   0:cb9a9f314b8b
     user:        test
     date:        Thu Jan 01 00:00:00 1970 +0000
     summary:     a
  

  $ hg histedit cb9a9f314b8b --commands - 2>&1 << EOF | fixbundle
  > pick cb9a9f314b8b a
  > pick ee283cb5f2d5 e
  > EOF
  hg: parse error: missing rules for changeset a4f7421b80f7
  (use "drop a4f7421b80f7" to discard, see also: 'hg help -e histedit.config')
  $ hg --config histedit.dropmissing=True histedit  cb9a9f314b8b --commands - 2>&1 << EOF | fixbundle
  > EOF
  hg: parse error: no rules provided
  (use strip extension to remove commits)
  $ hg --config histedit.dropmissing=True histedit  cb9a9f314b8b --commands - 2>&1 << EOF | fixbundle
  > pick cb9a9f314b8b a
  > pick ee283cb5f2d5 e
  > EOF
  $ hg log --graph
  @  changeset:   1:e99c679bf03e
  |  tag:         tip
  |  user:        test
  |  date:        Thu Jan 01 00:00:00 1970 +0000
  |  summary:     e
  |
  o  changeset:   0:cb9a9f314b8b
     user:        test
     date:        Thu Jan 01 00:00:00 1970 +0000
     summary:     a