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
$ testparseutil="$TESTDIR"/../contrib/testparseutil.py
Internal test by doctest
$ "$PYTHON" -m doctest "$testparseutil"
Tests for embedded python script
Typical cases
$ "$PYTHON" "$testparseutil" -v pyembedded <<NO_CHECK_EOF
> >>> for f in [1, 2, 3]:
> ... foo = 1
> >>> foo = 2
> $ echo "doctest is terminated by command, empty line, or comment"
> >>> foo = 31
> expected output of doctest fragment
> >>> foo = 32
>
> >>> foo = 33
>
> >>> foo = 34
> comment
> >>> foo = 35
>
> $ "\$PYTHON" <<EOF
> > foo = 4
> >
> > EOF
> $ cat > foo.py <<EOF
> > foo = 5
> > EOF
> $ cat >> foo.py <<EOF
> > foo = 6 # appended
> > EOF
>
> NO_CHECK_EOF limit mark makes parsing ignore corresponded fragment
> (this is useful to use bad code intentionally)
>
> $ "\$PYTHON" <<NO_CHECK_EOF
> > foo = 7 # this should be ignored at detection
> > NO_CHECK_EOF
> $ cat > foo.py <<NO_CHECK_EOF
> > foo = 8 # this should be ignored at detection
> > NO_CHECK_EOF
>
> doctest fragment ended by EOF
>
> >>> foo = 9
> NO_CHECK_EOF
<stdin>:1: <anonymous> starts
|for f in [1, 2, 3]:
| foo = 1
|foo = 2
<stdin>:4: <anonymous> ends
<stdin>:5: <anonymous> starts
|foo = 31
|
|foo = 32
|
|foo = 33
<stdin>:10: <anonymous> ends
<stdin>:11: <anonymous> starts
|foo = 34
<stdin>:12: <anonymous> ends
<stdin>:13: <anonymous> starts
|foo = 35
<stdin>:14: <anonymous> ends
<stdin>:16: <anonymous> starts
|foo = 4
|
<stdin>:18: <anonymous> ends
<stdin>:20: foo.py starts
|foo = 5
<stdin>:21: foo.py ends
<stdin>:23: foo.py starts
|foo = 6 # appended
<stdin>:24: foo.py ends
<stdin>:38: <anonymous> starts
|foo = 9
<stdin>:39: <anonymous> ends
Invalid test script
(similar test for shell script and hgrc configuration is omitted,
because this tests common base class of them)
$ "$PYTHON" "$testparseutil" -v pyembedded <<NO_CHECK_EOF > detected
> $ "\$PYTHON" <<EOF
> > foo = 1
>
> $ "\$PYTHON" <<EOF
> > foo = 2
> $ cat > bar.py <<EOF
> > bar = 2 # this fragment will be detected as expected
> > EOF
>
> $ cat > foo.py <<EOF
> > foo = 3
> NO_CHECK_EOF
<stdin>:3: unexpected line for "heredoc python invocation"
<stdin>:6: unexpected line for "heredoc python invocation"
<stdin>:11: unexpected end of file for "heredoc .py file"
[1]
$ cat detected
<stdin>:7: bar.py starts
|bar = 2 # this fragment will be detected as expected
<stdin>:8: bar.py ends
Tests for embedded shell script
$ "$PYTHON" "$testparseutil" -v shembedded <<NO_CHECK_EOF
> $ cat > foo.sh <<EOF
> > foo = 1
> >
> > foo = 2
> > EOF
> $ cat >> foo.sh <<EOF
> > foo = 3 # appended
> > EOF
>
> NO_CHECK_EOF limit mark makes parsing ignore corresponded fragment
> (this is useful to use bad code intentionally)
>
> $ cat > foo.sh <<NO_CHECK_EOF
> > # this should be ignored at detection
> > foo = 4
> > NO_CHECK_EOF
>
> NO_CHECK_EOF
<stdin>:2: foo.sh starts
|foo = 1
|
|foo = 2
<stdin>:5: foo.sh ends
<stdin>:7: foo.sh starts
|foo = 3 # appended
<stdin>:8: foo.sh ends
Tests for embedded hgrc configuration
$ "$PYTHON" "$testparseutil" -v hgrcembedded <<NO_CHECK_EOF
> $ cat > .hg/hgrc <<EOF
> > [ui]
> > verbose = true
> >
> > # end of local configuration
> > EOF
>
> $ cat > \$HGRCPATH <<EOF
> > [extensions]
> > rebase =
> > # end of global configuration
> > EOF
>
> $ cat >> \$HGRCPATH <<EOF
> > # appended
> > [extensions]
> > rebase =!
> > EOF
>
> NO_CHECK_EOF limit mark makes parsing ignore corresponded fragment
> (this is useful to use bad code intentionally)
>
> $ cat > .hg/hgrc <<NO_CHECK_EOF
> > # this local configuration should be ignored at detection
> > [ui]
> > username = foo bar
> > NO_CHECK_EOF
>
> $ cat > \$HGRCPATH <<NO_CHECK_EOF
> > # this global configuration should be ignored at detection
> > [extensions]
> > foobar =
> > NO_CHECK_EOF
> NO_CHECK_EOF
<stdin>:2: .hg/hgrc starts
|[ui]
|verbose = true
|
|# end of local configuration
<stdin>:6: .hg/hgrc ends
<stdin>:9: $HGRCPATH starts
|[extensions]
|rebase =
|# end of global configuration
<stdin>:12: $HGRCPATH ends
<stdin>:15: $HGRCPATH starts
|# appended
|[extensions]
|rebase =!
<stdin>:18: $HGRCPATH ends