view tests/test-hooklib-enforce_draft_commits.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

  $ cat <<EOF >> $HGRCPATH
  > [extensions]
  > hooklib =
  > 
  > [phases]
  > publish = False
  > EOF
  $ hg init a
  $ hg --cwd a debugbuilddag .
  $ hg --cwd a phase --public 0
  $ hg init b
  $ cat <<EOF >> b/.hg/hgrc
  > [hooks]
  > pretxnclose-phase.enforce_draft_commits = \
  >   python:hgext.hooklib.enforce_draft_commits.hook
  > EOF
  $ hg --cwd b pull ../a
  pulling from ../a
  requesting all changes
  adding changesets
  adding manifests
  adding file changes
  error: pretxnclose-phase.enforce_draft_commits hook failed: New changeset 1ea73414a91b in phase 'public' rejected
  transaction abort!
  rollback completed
  abort: New changeset 1ea73414a91b in phase 'public' rejected
  [255]
  $ hg --cwd a phase --force --draft 0
  $ hg --cwd b pull ../a
  pulling from ../a
  requesting all changes
  adding changesets
  adding manifests
  adding file changes
  added 1 changesets with 0 changes to 0 files
  new changesets 1ea73414a91b (1 drafts)
  (run 'hg update' to get a working copy)
  $ hg --cwd a phase --public 0
  $ hg --cwd b pull ../a
  pulling from ../a
  searching for changes
  no changes found
  error: pretxnclose-phase.enforce_draft_commits hook failed: Phase change from 'draft' to 'public' for 1ea73414a91b rejected
  abort: Phase change from 'draft' to 'public' for 1ea73414a91b rejected
  [255]