view tests/test-remotefilelog-sparse.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 no-windows

  $ . "$TESTDIR/remotefilelog-library.sh"

  $ hg init master
  $ cd master
  $ cat >> .hg/hgrc <<EOF
  > [remotefilelog]
  > server=True
  > EOF
  $ echo x > x
  $ echo z > z
  $ hg commit -qAm x1
  $ echo x2 > x
  $ echo z2 > z
  $ hg commit -qAm x2
  $ hg bookmark foo

  $ cd ..

# prefetch a revision w/ a sparse checkout

  $ hgcloneshallow ssh://user@dummy/master shallow --noupdate
  streaming all changes
  2 files to transfer, 527 bytes of data (no-zstd !)
  transferred 527 bytes in * seconds (* */sec) (glob) (no-zstd !)
  2 files to transfer, 534 bytes of data (zstd !)
  transferred 534 bytes in * seconds (* */sec) (glob) (zstd !)
  searching for changes
  no changes found
  $ cd shallow
  $ printf "[extensions]\nsparse=\n" >> .hg/hgrc

  $ hg debugsparse -I x
  $ hg prefetch -r 0
  1 files fetched over 1 fetches - (1 misses, 0.00% hit ratio) over *s (glob)

  $ hg cat -r 0 x
  x

  $ hg debugsparse -I z
  $ hg prefetch -r 0
  1 files fetched over 1 fetches - (1 misses, 0.00% hit ratio) over *s (glob)

  $ hg cat -r 0 z
  z

# prefetch sparse only on pull when configured

  $ printf "[remotefilelog]\npullprefetch=bookmark()\n" >> .hg/hgrc
  $ hg strip tip
  saved backup bundle to $TESTTMP/shallow/.hg/strip-backup/876b1317060d-b2e91d8d-backup.hg (glob)
  2 files fetched over 2 fetches - (2 misses, 0.00% hit ratio) over *s (glob)

  $ hg debugsparse --delete z

  $ clearcache
  $ hg pull
  pulling from ssh://user@dummy/master
  searching for changes
  adding changesets
  adding manifests
  adding file changes
  updating bookmark foo
  added 1 changesets with 0 changes to 0 files
  new changesets 876b1317060d
  (run 'hg update' to get a working copy)
  prefetching file contents
  1 files fetched over 1 fetches - (1 misses, 0.00% hit ratio) over *s (glob)

# Dont consider filtered files when doing copy tracing

## Push an unrelated commit
  $ cd ../

  $ hgcloneshallow ssh://user@dummy/master shallow2
  streaming all changes
  2 files to transfer, 527 bytes of data (no-zstd !)
  transferred 527 bytes in * seconds (*) (glob) (no-zstd !)
  2 files to transfer, 534 bytes of data (zstd !)
  transferred 534 bytes in * seconds (* */sec) (glob) (zstd !)
  searching for changes
  no changes found
  updating to branch default
  2 files updated, 0 files merged, 0 files removed, 0 files unresolved
  1 files fetched over 1 fetches - (1 misses, 0.00% hit ratio) over *s (glob)
  $ cd shallow2
  $ printf "[extensions]\nsparse=\n" >> .hg/hgrc

  $ hg up -q 0
  2 files fetched over 1 fetches - (2 misses, 0.00% hit ratio) over *s (glob)
  $ touch a
  $ hg ci -Aqm a
  $ hg push -q -f

## Pull the unrelated commit and rebase onto it - verify unrelated file was not
pulled

  $ cd ../shallow
  $ hg up -q 1
  $ hg pull -q
  $ hg debugsparse -I z
  $ clearcache
  $ hg prefetch -r '. + .^' -I x -I z
  4 files fetched over 1 fetches - (4 misses, 0.00% hit ratio) over * (glob)
  $ hg rebase -d 2 --keep
  rebasing 1:876b1317060d foo "x2"