tests/test-extension-timing.t

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-chg

Test basic extension support

  $ cat > foobar.py <<EOF
  > import os
  > from mercurial import commands, registrar
  > cmdtable = {}
  > command = registrar.command(cmdtable)
  > configtable = {}
  > configitem = registrar.configitem(configtable)
  > configitem(b'tests', b'foo', default=b"Foo")
  > def uisetup(ui):
  >     ui.debug(b"uisetup called [debug]\\n")
  >     ui.write(b"uisetup called\\n")
  >     ui.status(b"uisetup called [status]\\n")
  >     ui.flush()
  > def reposetup(ui, repo):
  >     ui.write(b"reposetup called for %s\\n" % os.path.basename(repo.root))
  >     ui.write(b"ui %s= repo.ui\\n" % (ui == repo.ui and b"=" or b"!"))
  >     ui.flush()
  > @command(b'foo', [], b'hg foo')
  > def foo(ui, *args, **kwargs):
  >     foo = ui.config(b'tests', b'foo')
  >     ui.write(foo)
  >     ui.write(b"\\n")
  > @command(b'bar', [], b'hg bar', norepo=True)
  > def bar(ui, *args, **kwargs):
  >     ui.write(b"Bar\\n")
  > EOF
  $ abspath=`pwd`/foobar.py

  $ mkdir barfoo
  $ cp foobar.py barfoo/__init__.py
  $ barfoopath=`pwd`/barfoo

  $ hg init a
  $ cd a
  $ echo foo > file
  $ hg add file
  $ hg commit -m 'add file'

  $ echo '[extensions]' >> $HGRCPATH
  $ echo "foobar = $abspath" >> $HGRCPATH

  $ filterlog () {
  >   sed -e 's!^[0-9/]* [0-9:]* ([0-9]*)>!YYYY/MM/DD HH:MM:SS (PID)>!'
  > }

Test extension setup timings

  $ hg foo --traceback --config devel.debug.extensions=yes --debug 2>&1 | filterlog
  YYYY/MM/DD HH:MM:SS (PID)> loading extensions
  YYYY/MM/DD HH:MM:SS (PID)> - processing 1 entries
  YYYY/MM/DD HH:MM:SS (PID)>   - loading extension: foobar
  YYYY/MM/DD HH:MM:SS (PID)>   > foobar extension loaded in * (glob)
  YYYY/MM/DD HH:MM:SS (PID)>     - validating extension tables: foobar
  YYYY/MM/DD HH:MM:SS (PID)>     - invoking registered callbacks: foobar
  YYYY/MM/DD HH:MM:SS (PID)>     > callbacks completed in * (glob)
  YYYY/MM/DD HH:MM:SS (PID)> > loaded 1 extensions, total time * (glob)
  YYYY/MM/DD HH:MM:SS (PID)> - loading configtable attributes
  YYYY/MM/DD HH:MM:SS (PID)> - executing uisetup hooks
  YYYY/MM/DD HH:MM:SS (PID)>   - running uisetup for foobar
  uisetup called [debug]
  uisetup called
  uisetup called [status]
  YYYY/MM/DD HH:MM:SS (PID)>   > uisetup for foobar took * (glob)
  YYYY/MM/DD HH:MM:SS (PID)> > all uisetup took * (glob)
  YYYY/MM/DD HH:MM:SS (PID)> - executing extsetup hooks
  YYYY/MM/DD HH:MM:SS (PID)>   - running extsetup for foobar
  YYYY/MM/DD HH:MM:SS (PID)>   > extsetup for foobar took * (glob)
  YYYY/MM/DD HH:MM:SS (PID)> > all extsetup took * (glob)
  YYYY/MM/DD HH:MM:SS (PID)> - executing remaining aftercallbacks
  YYYY/MM/DD HH:MM:SS (PID)> > remaining aftercallbacks completed in * (glob)
  YYYY/MM/DD HH:MM:SS (PID)> - loading extension registration objects
  YYYY/MM/DD HH:MM:SS (PID)> > extension registration object loading took * (glob)
  YYYY/MM/DD HH:MM:SS (PID)> > extension foobar take a total of * to load (glob)
  YYYY/MM/DD HH:MM:SS (PID)> extension loading complete
  YYYY/MM/DD HH:MM:SS (PID)> loading additional extensions
  YYYY/MM/DD HH:MM:SS (PID)> - processing 1 entries
  YYYY/MM/DD HH:MM:SS (PID)> > loaded 0 extensions, total time * (glob)
  YYYY/MM/DD HH:MM:SS (PID)> - loading configtable attributes
  YYYY/MM/DD HH:MM:SS (PID)> - executing uisetup hooks
  YYYY/MM/DD HH:MM:SS (PID)> > all uisetup took * (glob)
  YYYY/MM/DD HH:MM:SS (PID)> - executing extsetup hooks
  YYYY/MM/DD HH:MM:SS (PID)> > all extsetup took * (glob)
  YYYY/MM/DD HH:MM:SS (PID)> - executing remaining aftercallbacks
  YYYY/MM/DD HH:MM:SS (PID)> > remaining aftercallbacks completed in * (glob)
  YYYY/MM/DD HH:MM:SS (PID)> - loading extension registration objects
  YYYY/MM/DD HH:MM:SS (PID)> > extension registration object loading took * (glob)
  YYYY/MM/DD HH:MM:SS (PID)> extension loading complete
  YYYY/MM/DD HH:MM:SS (PID)> - executing reposetup hooks
  YYYY/MM/DD HH:MM:SS (PID)>   - running reposetup for foobar
  reposetup called for a
  ui == repo.ui
  YYYY/MM/DD HH:MM:SS (PID)>   > reposetup for foobar took * (glob)
  YYYY/MM/DD HH:MM:SS (PID)> > all reposetup took * (glob)
  Foo

  $ cd ..

  $ echo 'foobar = !' >> $HGRCPATH