view tests/test-py3-commands.t @ 35569:964212780daf

rust: implementation of `hg`

This commit provides a mostly-working implementation of the
`hg` script in Rust along with scaffolding to support Rust in
the repository.

If you are familiar with Rust, the contents of the added rust/
directory should be pretty straightforward. We create an "hgcli"
package that implements a binary application to run Mercurial.
The output of this package is an "hg" binary.

Our Rust `hg` (henceforth "rhg") essentially is a port of the existing
`hg` Python script. The main difference is the creation of the embedded
CPython interpreter is handled by the binary itself instead of relying
on the shebang. In that sense, rhg is more similar to the "exe wrapper"
we currently use on Windows. However, unlike the exe wrapper, rhg does
not call the `hg` Python script. Instead, it uses the CPython APIs to
import mercurial modules and call appropriate functions. The amount of
code here is surprisingly small.

It is my intent to replace the existing C-based exe wrapper with rhg.
Preferably in the next Mercurial release. This should be achievable -
at least for some Mercurial distributions. The future/timeline for
rhg on other platforms is less clear. We already ship a hg.exe on
Windows. So if we get the quirks with Rust worked out, shipping a
Rust-based hg.exe should hopefully not be too contentious.

Now onto the implementation.

We're using python27-sys and the cpython crates for talking to the
CPython API. We currently don't use too much functionality of the
cpython crate and could have probably cut it out. However, it does
provide a reasonable abstraction over unsafe {} CPython function
calls. While we still have our fair share of those, at least we're
not dealing with too much refcounting, error checking, etc. So I
think the use of the cpython crate is justified. Plus, there is
not-yet-implemented functionality that could benefit from cpython. I
see our use of this crate only increasing.

The cpython and python27-sys crates are not without their issues.
The cpython crate didn't seem to account for the embedding use case
in its design. Instead, it seems to assume that you are building
a Python extension. It is making some questionable decisions around
certain CPython APIs. For example, it insists that
PyEval_ThreadsInitialized() is called and that the Python code
likely isn't the main thread in the underlying application. It
is also missing some functionality that is important for embedded
use cases (such as exporting the path to the Python interpreter
from its build script). After spending several hours trying to
wrangle python27-sys and cpython, I gave up and forked the project
on GitHub. Our Cargo.toml tracks this fork. I'm optimistic that
the upstream project will accept our contributions and we can
eventually unfork.

There is a non-trivial amount of code in our custom Cargo build
script. Our build.rs (which is called as part of building the hgcli
crate):

* Validates that the Python interpreter that was detected by the
  python27-sys crate provides a shared library (we only support
  shared library linking at this time - although this restriction
  could be loosened).
* Validates that the Python is built with UCS-4 support. This ensures
  maximum Unicode compatibility.
* Exports variables to the crate build allowing the built crate to e.g.
  find the path to the Python interpreter.

The produced rhg should be considered alpha quality. There are several
known deficiencies. Many of these are documented with inline TODOs.

Probably the biggest limitation of rhg is that it assumes it is
running from the ./rust/target/<target> directory of a source
distribution. So, rhg is currently not very practical for real-world
use. But, if you can `cargo build` it, running the binary *should*
yield a working Mercurial CLI.

In order to support using rhg with the test harness, we needed to hack
up run-tests.py so the path to Mercurial's Python files is set properly.
The change is extremely hacky and is only intended to be a stop-gap
until the test harness gains first-class support for installing rhg.
This will likely occur after we support running rhg outside the
source directory.

Despite its officially alpha quality, rhg copes extremely well with
the test harness (at least on Linux). Using
`run-tests.py --with-hg ../rust/target/debug/hg`, I only encounter
the following failures:

* test-run-tests.t -- Warnings emitted about using an unexpected
  Mercurial library. This is due to the hacky nature of setting the
  Python directory when run-tests.py detected rhg.
* test-devel-warnings.t -- Expected stack trace missing frame for `hg`
  (This is expected since we no longer have an `hg` script!)
* test-convert.t -- Test running `$PYTHON "$BINDIR"/hg`, which obviously
  assumes `hg` is a Python script.
* test-merge-tools.t -- Same assumption about `hg` being executable with
  Python.
* test-http-bad-server.t -- Seeing exit code 255 instead of 1 around
  line 358.
* test-blackbox.t -- Exit code 255 instead of 1.
* test-basic.t -- Exit code 255 instead of 1.

It certainly looks like we have a bug around exit code handling. I
don't think it is severe enough to hold up review and landing of this
initial implementation. Perfect is the enemy of good.

Differential Revision: https://phab.mercurial-scm.org/D1581

#require py3exe

This test helps in keeping a track on which commands we can run on
Python 3 and see what kind of errors are coming up.
The full traceback is hidden to have a stable output.
  $ HGBIN=`which hg`

  $ for cmd in version debuginstall ; do
  >   echo $cmd
  >   $PYTHON3 $HGBIN $cmd 2>&1 2>&1 | tail -1
  > done
  version
  warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
  debuginstall
  no problems detected

#if test-repo
Make a clone so that any features in the developer's .hg/hgrc that
might confuse Python 3 don't break this test. When we can do commit in
Python 3, we'll stop doing this. We use e76ed1e480ef for the clone
because it has different files than 273ce12ad8f1, so we can test both
`files` from dirstate and `files` loaded from a specific revision.

  $ hg clone -r e76ed1e480ef "`dirname "$TESTDIR"`" testrepo 2>&1 | tail -1
  15 files updated, 0 files merged, 0 files removed, 0 files unresolved

Test using -R, which exercises some URL code:
  $ $PYTHON3 $HGBIN -R testrepo files -r 273ce12ad8f1 | tail -1
  testrepo/tkmerge

Now prove `hg files` is reading the whole manifest. We have to grep
out some potential warnings that come from hgrc as yet.
  $ cd testrepo
  $ $PYTHON3 $HGBIN files -r 273ce12ad8f1
  .hgignore
  PKG-INFO
  README
  hg
  mercurial/__init__.py
  mercurial/byterange.py
  mercurial/fancyopts.py
  mercurial/hg.py
  mercurial/mdiff.py
  mercurial/revlog.py
  mercurial/transaction.py
  notes.txt
  setup.py
  tkmerge

  $ $PYTHON3 $HGBIN files -r 273ce12ad8f1 | wc -l
  \s*14 (re)
  $ $PYTHON3 $HGBIN files | wc -l
  \s*15 (re)

Test if log-like commands work:

  $ $PYTHON3 $HGBIN tip
  changeset:   10:e76ed1e480ef
  tag:         tip
  user:        [e-mail]
  date:        Tue May 03 23:37:43 2005 -0800
  summary:     Fix linking of changeset revs when merging
  

  $ $PYTHON3 $HGBIN log -r0
  changeset:   0:9117c6561b0b
  user:        [e-mail]
  date:        Tue May 03 13:16:10 2005 -0800
  summary:     Add back links from file revisions to changeset revisions
  

  $ cd ..
#endif

Test if `hg config` works:

  $ $PYTHON3 $HGBIN config
  devel.all-warnings=true
  devel.default-date=0 0
  largefiles.usercache=$TESTTMP/.cache/largefiles
  ui.slash=True
  ui.interactive=False
  ui.mergemarkers=detailed
  ui.promptecho=True
  web.address=localhost
  web.ipv6=False

  $ cat > included-hgrc <<EOF
  > [extensions]
  > babar = imaginary_elephant
  > EOF
  $ cat >> $HGRCPATH <<EOF
  > %include $TESTTMP/included-hgrc
  > EOF
  $ $PYTHON3 $HGBIN version | tail -1
  *** failed to import extension babar from imaginary_elephant: *: 'imaginary_elephant' (glob)
  warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

  $ rm included-hgrc
  $ touch included-hgrc

Test bytes-ness of policy.policy with HGMODULEPOLICY

  $ HGMODULEPOLICY=py
  $ export HGMODULEPOLICY
  $ $PYTHON3 `which hg` debuginstall 2>&1 2>&1 | tail -1
  no problems detected

`hg init` can create empty repos
`hg status works fine`
`hg summary` also works!

  $ $PYTHON3 `which hg` init py3repo
  $ cd py3repo
  $ echo "This is the file 'iota'." > iota
  $ $PYTHON3 $HGBIN status
  ? iota
  $ $PYTHON3 $HGBIN add iota
  $ $PYTHON3 $HGBIN status
  A iota
  $ hg diff --nodates --git
  diff --git a/iota b/iota
  new file mode 100644
  --- /dev/null
  +++ b/iota
  @@ -0,0 +1,1 @@
  +This is the file 'iota'.
  $ $PYTHON3 $HGBIN commit --message 'commit performed in Python 3'
  $ $PYTHON3 $HGBIN status

  $ mkdir A
  $ echo "This is the file 'mu'." > A/mu
  $ $PYTHON3 $HGBIN addremove
  adding A/mu
  $ $PYTHON3 $HGBIN status
  A A/mu
  $ HGEDITOR='echo message > ' $PYTHON3 $HGBIN commit
  $ $PYTHON3 $HGBIN status
  $ $PYHON3 $HGBIN summary
  parent: 1:e1e9167203d4 tip
   message
  branch: default
  commit: (clean)
  update: (current)
  phases: 2 draft

Test weird unicode-vs-bytes stuff

  $ $PYTHON3 $HGBIN help | egrep -v '^ |^$'
  Mercurial Distributed SCM
  list of commands:
  additional help topics:
  (use 'hg help -v' to show built-in aliases and global options)

  $ $PYTHON3 $HGBIN help help | egrep -v '^ |^$'
  hg help [-ecks] [TOPIC]
  show help for a given topic or a help overview
  options ([+] can be repeated):
  (some details hidden, use --verbose to show complete help)

  $ $PYTHON3 $HGBIN help -k notopic
  abort: no matches
  (try 'hg help' for a list of topics)
  [255]

Prove the repo is valid using the Python 2 `hg`:
  $ hg verify
  checking changesets
  checking manifests
  crosschecking files in changesets and manifests
  checking files
  2 files, 2 changesets, 2 total revisions
  $ hg log
  changeset:   1:e1e9167203d4
  tag:         tip
  user:        test
  date:        Thu Jan 01 00:00:00 1970 +0000
  summary:     message
  
  changeset:   0:71c96e924262
  user:        test
  date:        Thu Jan 01 00:00:00 1970 +0000
  summary:     commit performed in Python 3
  

  $ $PYTHON3 $HGBIN log -G
  @  changeset:   1:e1e9167203d4
  |  tag:         tip
  |  user:        test
  |  date:        Thu Jan 01 00:00:00 1970 +0000
  |  summary:     message
  |
  o  changeset:   0:71c96e924262
     user:        test
     date:        Thu Jan 01 00:00:00 1970 +0000
     summary:     commit performed in Python 3
  
  $ $PYTHON3 $HGBIN log -Tjson
  [
   {
    "rev": 1,
    "node": "e1e9167203d450ca2f558af628955b5f5afd4489",
    "branch": "default",
    "phase": "draft",
    "user": "test",
    "date": [0, 0],
    "desc": "message",
    "bookmarks": [],
    "tags": ["tip"],
    "parents": ["71c96e924262969ff0d8d3d695b0f75412ccc3d8"]
   },
   {
    "rev": 0,
    "node": "71c96e924262969ff0d8d3d695b0f75412ccc3d8",
    "branch": "default",
    "phase": "draft",
    "user": "test",
    "date": [0, 0],
    "desc": "commit performed in Python 3",
    "bookmarks": [],
    "tags": [],
    "parents": ["0000000000000000000000000000000000000000"]
   }
  ]

Show that update works now!

  $ $PYTHON3 $HGBIN up 0
  0 files updated, 0 files merged, 1 files removed, 0 files unresolved
  $ $PYTHON3 $HGBIN identify
  71c96e924262

branches and bookmarks also works!

  $ $PYTHON3 $HGBIN branches
  default                        1:e1e9167203d4
  $ $PYTHON3 $HGBIN bookmark book
  $ $PYTHON3 $HGBIN bookmarks
   * book                      0:71c96e924262