view tests/test-completion.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

Show all commands except debug commands
  $ hg debugcomplete
  add
  addremove
  annotate
  archive
  backout
  bisect
  bookmarks
  branch
  branches
  bundle
  cat
  clone
  commit
  config
  copy
  diff
  export
  files
  forget
  graft
  grep
  heads
  help
  identify
  import
  incoming
  init
  locate
  log
  manifest
  merge
  outgoing
  parents
  paths
  phase
  pull
  push
  recover
  remove
  rename
  resolve
  revert
  rollback
  root
  serve
  status
  summary
  tag
  tags
  tip
  unbundle
  update
  verify
  version

Show all commands that start with "a"
  $ hg debugcomplete a
  add
  addremove
  annotate
  archive

Do not show debug commands if there are other candidates
  $ hg debugcomplete d
  diff

Show debug commands if there are no other candidates
  $ hg debugcomplete debug
  debugancestor
  debugapplystreamclonebundle
  debugbuilddag
  debugbundle
  debugcapabilities
  debugcheckstate
  debugcolor
  debugcommands
  debugcomplete
  debugconfig
  debugcreatestreamclonebundle
  debugdag
  debugdata
  debugdate
  debugdeltachain
  debugdirstate
  debugdiscovery
  debugdownload
  debugextensions
  debugfileset
  debugformat
  debugfsinfo
  debuggetbundle
  debugignore
  debugindex
  debugindexdot
  debuginstall
  debugknown
  debuglabelcomplete
  debuglocks
  debugmergestate
  debugnamecomplete
  debugobsolete
  debugpathcomplete
  debugpickmergetool
  debugpushkey
  debugpvec
  debugrebuilddirstate
  debugrebuildfncache
  debugrename
  debugrevlog
  debugrevspec
  debugsetparents
  debugssl
  debugsub
  debugsuccessorssets
  debugtemplate
  debugupdatecaches
  debugupgraderepo
  debugwalk
  debugwireargs

Do not show the alias of a debug command if there are other candidates
(this should hide rawcommit)
  $ hg debugcomplete r
  recover
  remove
  rename
  resolve
  revert
  rollback
  root
Show the alias of a debug command if there are no other candidates
  $ hg debugcomplete rawc
  

Show the global options
  $ hg debugcomplete --options | sort
  --color
  --config
  --cwd
  --debug
  --debugger
  --encoding
  --encodingmode
  --help
  --hidden
  --noninteractive
  --pager
  --profile
  --quiet
  --repository
  --time
  --traceback
  --verbose
  --version
  -R
  -h
  -q
  -v
  -y

Show the options for the "serve" command
  $ hg debugcomplete --options serve | sort
  --accesslog
  --address
  --certificate
  --cmdserver
  --color
  --config
  --cwd
  --daemon
  --daemon-postexec
  --debug
  --debugger
  --encoding
  --encodingmode
  --errorlog
  --help
  --hidden
  --ipv6
  --name
  --noninteractive
  --pager
  --pid-file
  --port
  --prefix
  --profile
  --quiet
  --repository
  --stdio
  --style
  --subrepos
  --templates
  --time
  --traceback
  --verbose
  --version
  --web-conf
  -6
  -A
  -E
  -R
  -S
  -a
  -d
  -h
  -n
  -p
  -q
  -t
  -v
  -y

Show an error if we use --options with an ambiguous abbreviation
  $ hg debugcomplete --options s
  hg: command 's' is ambiguous:
      serve showconfig status summary
  [255]

Show all commands + options
  $ hg debugcommands
  add: include, exclude, subrepos, dry-run
  annotate: rev, follow, no-follow, text, user, file, date, number, changeset, line-number, skip, ignore-all-space, ignore-space-change, ignore-blank-lines, ignore-space-at-eol, include, exclude, template
  clone: noupdate, updaterev, rev, branch, pull, uncompressed, stream, ssh, remotecmd, insecure
  commit: addremove, close-branch, amend, secret, edit, interactive, include, exclude, message, logfile, date, user, subrepos
  diff: rev, change, text, git, binary, nodates, noprefix, show-function, reverse, ignore-all-space, ignore-space-change, ignore-blank-lines, ignore-space-at-eol, unified, stat, root, include, exclude, subrepos
  export: output, switch-parent, rev, text, git, binary, nodates
  forget: include, exclude
  init: ssh, remotecmd, insecure
  log: follow, follow-first, date, copies, keyword, rev, line-range, removed, only-merges, user, only-branch, branch, prune, patch, git, limit, no-merges, stat, graph, style, template, include, exclude
  merge: force, rev, preview, tool
  pull: update, force, rev, bookmark, branch, ssh, remotecmd, insecure
  push: force, rev, bookmark, branch, new-branch, pushvars, ssh, remotecmd, insecure
  remove: after, force, subrepos, include, exclude
  serve: accesslog, daemon, daemon-postexec, errorlog, port, address, prefix, name, web-conf, webdir-conf, pid-file, stdio, cmdserver, templates, style, ipv6, certificate, subrepos
  status: all, modified, added, removed, deleted, clean, unknown, ignored, no-status, terse, copies, print0, rev, change, include, exclude, subrepos, template
  summary: remote
  update: clean, check, merge, date, rev, tool
  addremove: similarity, subrepos, include, exclude, dry-run
  archive: no-decode, prefix, rev, type, subrepos, include, exclude
  backout: merge, commit, no-commit, parent, rev, edit, tool, include, exclude, message, logfile, date, user
  bisect: reset, good, bad, skip, extend, command, noupdate
  bookmarks: force, rev, delete, rename, inactive, template
  branch: force, clean
  branches: active, closed, template
  bundle: force, rev, branch, base, all, type, ssh, remotecmd, insecure
  cat: output, rev, decode, include, exclude, template
  config: untrusted, edit, local, global, template
  copy: after, force, include, exclude, dry-run
  debugancestor: 
  debugapplystreamclonebundle: 
  debugbuilddag: mergeable-file, overwritten-file, new-file
  debugbundle: all, part-type, spec
  debugcapabilities: 
  debugcheckstate: 
  debugcolor: style
  debugcommands: 
  debugcomplete: options
  debugcreatestreamclonebundle: 
  debugdag: tags, branches, dots, spaces
  debugdata: changelog, manifest, dir
  debugdate: extended
  debugdeltachain: changelog, manifest, dir, template
  debugdirstate: nodates, datesort
  debugdiscovery: old, nonheads, rev, ssh, remotecmd, insecure
  debugdownload: output
  debugextensions: template
  debugfileset: rev
  debugformat: template
  debugfsinfo: 
  debuggetbundle: head, common, type
  debugignore: 
  debugindex: changelog, manifest, dir, format
  debugindexdot: changelog, manifest, dir
  debuginstall: template
  debugknown: 
  debuglabelcomplete: 
  debuglocks: force-lock, force-wlock, set-lock, set-wlock
  debugmergestate: 
  debugnamecomplete: 
  debugobsolete: flags, record-parents, rev, exclusive, index, delete, date, user, template
  debugpathcomplete: full, normal, added, removed
  debugpickmergetool: rev, changedelete, include, exclude, tool
  debugpushkey: 
  debugpvec: 
  debugrebuilddirstate: rev, minimal
  debugrebuildfncache: 
  debugrename: rev
  debugrevlog: changelog, manifest, dir, dump
  debugrevspec: optimize, show-revs, show-set, show-stage, no-optimized, verify-optimized
  debugsetparents: 
  debugssl: 
  debugsub: rev
  debugsuccessorssets: closest
  debugtemplate: rev, define
  debugupdatecaches: 
  debugupgraderepo: optimize, run
  debugwalk: include, exclude
  debugwireargs: three, four, five, ssh, remotecmd, insecure
  files: rev, print0, include, exclude, template, subrepos
  graft: rev, continue, edit, log, force, currentdate, currentuser, date, user, tool, dry-run
  grep: print0, all, text, follow, ignore-case, files-with-matches, line-number, rev, user, date, template, include, exclude
  heads: rev, topo, active, closed, style, template
  help: extension, command, keyword, system
  identify: rev, num, id, branch, tags, bookmarks, ssh, remotecmd, insecure, template
  import: strip, base, edit, force, no-commit, bypass, partial, exact, prefix, import-branch, message, logfile, date, user, similarity
  incoming: force, newest-first, bundle, rev, bookmarks, branch, patch, git, limit, no-merges, stat, graph, style, template, ssh, remotecmd, insecure, subrepos
  locate: rev, print0, fullpath, include, exclude
  manifest: rev, all, template
  outgoing: force, rev, newest-first, bookmarks, branch, patch, git, limit, no-merges, stat, graph, style, template, ssh, remotecmd, insecure, subrepos
  parents: rev, style, template
  paths: template
  phase: public, draft, secret, force, rev
  recover: 
  rename: after, force, include, exclude, dry-run
  resolve: all, list, mark, unmark, no-status, tool, include, exclude, template
  revert: all, date, rev, no-backup, interactive, include, exclude, dry-run
  rollback: dry-run, force
  root: 
  tag: force, local, rev, remove, edit, message, date, user
  tags: template
  tip: patch, git, style, template
  unbundle: update
  verify: 
  version: template

  $ hg init a
  $ cd a
  $ echo fee > fee
  $ hg ci -q -Amfee
  $ hg tag fee
  $ mkdir fie
  $ echo dead > fie/dead
  $ echo live > fie/live
  $ hg bookmark fo
  $ hg branch -q fie
  $ hg ci -q -Amfie
  $ echo fo > fo
  $ hg branch -qf default
  $ hg ci -q -Amfo
  $ echo Fum > Fum
  $ hg ci -q -AmFum
  $ hg bookmark Fum

Test debugpathcomplete

  $ hg debugpathcomplete f
  fee
  fie
  fo
  $ hg debugpathcomplete -f f
  fee
  fie/dead
  fie/live
  fo

  $ hg rm Fum
  $ hg debugpathcomplete -r F
  Fum

Test debugnamecomplete

  $ hg debugnamecomplete
  Fum
  default
  fee
  fie
  fo
  tip
  $ hg debugnamecomplete f
  fee
  fie
  fo

Test debuglabelcomplete, a deprecated name for debugnamecomplete that is still
used for completions in some shells.

  $ hg debuglabelcomplete
  Fum
  default
  fee
  fie
  fo
  tip
  $ hg debuglabelcomplete f
  fee
  fie
  fo