view tests/test-rhg-sparse-narrow.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 rhg

  $ NO_FALLBACK="env RHG_ON_UNSUPPORTED=abort"

Rhg works well when sparse working copy is enabled.

  $ cd "$TESTTMP"
  $ hg init repo-sparse
  $ cd repo-sparse
  $ cat > .hg/hgrc <<EOF
  > [extensions]
  > sparse=
  > EOF

  $ echo a > show
  $ echo x > hide
  $ mkdir dir1 dir2
  $ echo x > dir1/x
  $ echo y > dir1/y
  $ echo z > dir2/z

  $ hg ci -Aqm 'initial'
  $ hg debugsparse --include 'show'
  $ ls -A
  .hg
  show

  $ tip=$(hg log -r . --template '{node}')
  $ $NO_FALLBACK rhg files -r "$tip"
  dir1/x
  dir1/y
  dir2/z
  hide
  show
  $ $NO_FALLBACK rhg files
  show

  $ $NO_FALLBACK rhg cat -r "$tip" hide
  x

  $ cd ..

We support most things when narrow is enabled, too, with a couple of caveats.

  $ . "$TESTDIR/narrow-library.sh"
  $ real_hg=$RHG_FALLBACK_EXECUTABLE

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

  $ hg clone --narrow  ./repo-sparse repo-narrow --include dir1
  requesting all changes
  adding changesets
  adding manifests
  adding file changes
  added 1 changesets with 2 changes to 2 files
  new changesets 6d714a4a2998
  updating to branch default
  2 files updated, 0 files merged, 0 files removed, 0 files unresolved

  $ cd repo-narrow

  $ $NO_FALLBACK rhg cat -r "$tip" dir1/x
  x
  $ "$real_hg" cat -r "$tip" dir1/x
  x

TODO: bad error message

  $ $NO_FALLBACK rhg cat -r "$tip" hide
  abort: invalid revision identifier: 6d714a4a2998cbfd0620db44da58b749f6565d63
  [255]
  $ "$real_hg" cat -r "$tip" hide
  [1]

A naive implementation of [rhg files] leaks the paths that are supposed to be
hidden by narrow, so we just fall back to hg.

  $ $NO_FALLBACK rhg files -r "$tip"
  unsupported feature: rhg files -r <rev> is not supported in narrow clones
  [252]
  $ "$real_hg" files -r "$tip"
  dir1/x
  dir1/y

Hg status needs to do some filtering based on narrow spec, so we don't
support it in rhg for narrow clones yet.

  $ mkdir dir2
  $ touch dir2/q
  $ "$real_hg" status
  $ $NO_FALLBACK rhg --config rhg.status=true status
  unsupported feature: rhg status is not supported for sparse checkouts or narrow clones yet
  [252]

Adding "orphaned" index files:

  $ (cd ..; cp repo-sparse/.hg/store/data/hide.i repo-narrow/.hg/store/data/hide.i)
  $ (cd ..; mkdir repo-narrow/.hg/store/data/dir2; cp repo-sparse/.hg/store/data/dir2/z.i repo-narrow/.hg/store/data/dir2/z.i)
  $ "$real_hg" verify
  checking changesets
  checking manifests
  crosschecking files in changesets and manifests
  checking files
  checked 1 changesets with 2 changes to 2 files

  $ "$real_hg" files -r "$tip"
  dir1/x
  dir1/y

# TODO: even though [hg files] hides the orphaned dir2/z, [hg cat] still shows it.
# rhg has the same issue, but at least it's not specific to rhg.
# This is despite [hg verify] succeeding above.

  $ $NO_FALLBACK rhg cat -r "$tip" dir2/z
  z
  $ "$real_hg" cat -r "$tip" dir2/z
  z