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view tests/test-remotefilelog-pull-noshallow.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
author | Raphaël Gomès <rgomes@octobus.net> |
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date | Tue, 05 Apr 2022 10:55:28 +0200 |
parents | 52fbf8a9907c |
children |
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#require no-windows $ . "$TESTDIR/remotefilelog-library.sh" Set up an extension to make sure remotefilelog clientsetup() runs unconditionally even if we have never used a local shallow repo. This mimics behavior when using remotefilelog with chg. clientsetup() can be triggered due to a shallow repo, and then the code can later interact with non-shallow repositories. $ cat > setupremotefilelog.py << EOF > from mercurial import extensions > def extsetup(ui): > remotefilelog = extensions.find(b'remotefilelog') > remotefilelog.onetimeclientsetup(ui) > EOF Set up the master repository to pull from. $ hg init master $ cd master $ cat >> .hg/hgrc <<EOF > [remotefilelog] > server=True > EOF $ echo x > x $ hg commit -qAm x $ cd .. $ hg clone ssh://user@dummy/master child -q We should see the remotefilelog capability here, which advertises that the server supports our custom getfiles method. $ cd master $ echo 'hello' | hg -R . serve --stdio | grep capa | identifyrflcaps exp-remotefilelog-ssh-getfiles-1 x_rfl_getfile x_rfl_getflogheads $ echo 'capabilities' | hg -R . serve --stdio | identifyrflcaps ; echo exp-remotefilelog-ssh-getfiles-1 x_rfl_getfile x_rfl_getflogheads Pull to the child repository. Use our custom setupremotefilelog extension to ensure that remotefilelog.onetimeclientsetup() gets triggered. (Without using chg it normally would not be run in this case since the local repository is not shallow.) $ echo y > y $ hg commit -qAm y $ cd ../child $ hg pull --config extensions.setuprfl=$TESTTMP/setupremotefilelog.py pulling from ssh://user@dummy/master searching for changes adding changesets adding manifests adding file changes added 1 changesets with 1 changes to 1 files new changesets d34c38483be9 (run 'hg update' to get a working copy) $ hg up 1 files updated, 0 files merged, 0 files removed, 0 files unresolved $ cat y y Test that bundle works in a non-remotefilelog repo w/ remotefilelog loaded $ echo y >> y $ hg commit -qAm "modify y" $ hg bundle --base ".^" --rev . mybundle.hg --config extensions.setuprfl=$TESTTMP/setupremotefilelog.py 1 changesets found $ cd ..