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
test that a commit clears the merge state.
$ hg init repo
$ cd repo
$ echo foo > file1
$ echo foo > file2
$ hg commit -Am 'add files'
adding file1
adding file2
$ echo bar >> file1
$ echo bar >> file2
$ hg commit -Am 'append bar to files'
create a second head with conflicting edits
$ hg up -C 0
2 files updated, 0 files merged, 0 files removed, 0 files unresolved
$ echo baz >> file1
$ echo baz >> file2
$ hg commit -Am 'append baz to files'
created new head
create a third head with no conflicting edits
$ hg up -qC 0
$ echo foo > file3
$ hg commit -Am 'add non-conflicting file'
adding file3
created new head
failing merge
$ hg up -qC 2
$ hg merge --tool=internal:fail 1
0 files updated, 0 files merged, 0 files removed, 2 files unresolved
use 'hg resolve' to retry unresolved file merges or 'hg update -C .' to abandon
[1]
resolve -l should contain unresolved entries
$ hg resolve -l
U file1
U file2
$ hg resolve -l --no-status
file1
file2
resolving an unknown path should emit a warning, but not for -l
$ hg resolve -m does-not-exist
arguments do not match paths that need resolving
$ hg resolve -l does-not-exist
tell users how they could have used resolve
$ mkdir nested
$ cd nested
$ hg resolve -m file1
arguments do not match paths that need resolving
(try: hg resolve -m path:file1)
$ hg resolve -m file1 filez
arguments do not match paths that need resolving
(try: hg resolve -m path:file1 path:filez)
$ hg resolve -m path:file1 path:filez
$ hg resolve -l
R file1
U file2
$ hg resolve -m filez file2
arguments do not match paths that need resolving
(try: hg resolve -m path:filez path:file2)
$ hg resolve -m path:filez path:file2
(no more unresolved files)
$ hg resolve -l
R file1
R file2
cleanup
$ hg resolve -u
$ cd ..
$ rmdir nested
don't allow marking or unmarking driver-resolved files
$ cat > $TESTTMP/markdriver.py << EOF
> '''mark and unmark files as driver-resolved'''
> from mercurial import merge, registrar, scmutil
> cmdtable = {}
> command = registrar.command(cmdtable)
> @command(b'markdriver',
> [('u', 'unmark', None, '')],
> 'FILE...')
> def markdriver(ui, repo, *pats, **opts):
> wlock = repo.wlock()
> try:
> ms = merge.mergestate.read(repo)
> m = scmutil.match(repo[None], pats, opts)
> for f in ms:
> if not m(f):
> continue
> if not opts['unmark']:
> ms.mark(f, 'd')
> else:
> ms.mark(f, 'u')
> ms.commit()
> finally:
> wlock.release()
> EOF
$ hg --config extensions.markdriver=$TESTTMP/markdriver.py markdriver file1
$ hg resolve --list
D file1
U file2
$ hg resolve --mark file1
not marking file1 as it is driver-resolved
this should not print out file1
$ hg resolve --mark --all
(no more unresolved files -- run "hg resolve --all" to conclude)
$ hg resolve --mark 'glob:file*'
(no more unresolved files -- run "hg resolve --all" to conclude)
$ hg resolve --list
D file1
R file2
$ hg resolve --unmark file1
not unmarking file1 as it is driver-resolved
(no more unresolved files -- run "hg resolve --all" to conclude)
$ hg resolve --unmark --all
$ hg resolve --list
D file1
U file2
$ hg --config extensions.markdriver=$TESTTMP/markdriver.py markdriver --unmark file1
$ hg resolve --list
U file1
U file2
resolve the failure
$ echo resolved > file1
$ hg resolve -m file1
resolve -l should show resolved file as resolved
$ hg resolve -l
R file1
U file2
$ hg resolve -l -Tjson
[
{
"path": "file1",
"status": "R"
},
{
"path": "file2",
"status": "U"
}
]
resolve -m without paths should mark all resolved
$ hg resolve -m
(no more unresolved files)
$ hg commit -m 'resolved'
resolve -l should be empty after commit
$ hg resolve -l
$ hg resolve -l -Tjson
[
]
resolve --all should abort when no merge in progress
$ hg resolve --all
abort: resolve command not applicable when not merging
[255]
resolve -m should abort when no merge in progress
$ hg resolve -m
abort: resolve command not applicable when not merging
[255]
can not update or merge when there are unresolved conflicts
$ hg up -qC 0
$ echo quux >> file1
$ hg up 1
merging file1
warning: conflicts while merging file1! (edit, then use 'hg resolve --mark')
1 files updated, 0 files merged, 0 files removed, 1 files unresolved
use 'hg resolve' to retry unresolved file merges
[1]
$ hg up 0
abort: outstanding merge conflicts
[255]
$ hg merge 2
abort: outstanding merge conflicts
[255]
$ hg merge --force 2
abort: outstanding merge conflicts
[255]
set up conflict-free merge
$ hg up -qC 3
$ hg merge 1
2 files updated, 0 files merged, 0 files removed, 0 files unresolved
(branch merge, don't forget to commit)
resolve --all should do nothing in merge without conflicts
$ hg resolve --all
(no more unresolved files)
resolve -m should do nothing in merge without conflicts
$ hg resolve -m
(no more unresolved files)
get back to conflicting state
$ hg up -qC 2
$ hg merge --tool=internal:fail 1
0 files updated, 0 files merged, 0 files removed, 2 files unresolved
use 'hg resolve' to retry unresolved file merges or 'hg update -C .' to abandon
[1]
resolve without arguments should suggest --all
$ hg resolve
abort: no files or directories specified
(use --all to re-merge all unresolved files)
[255]
resolve --all should re-merge all unresolved files
$ hg resolve --all
merging file1
merging file2
warning: conflicts while merging file1! (edit, then use 'hg resolve --mark')
warning: conflicts while merging file2! (edit, then use 'hg resolve --mark')
[1]
$ cat file1.orig
foo
baz
$ cat file2.orig
foo
baz
.orig files should exists where specified
$ hg resolve --all --verbose --config 'ui.origbackuppath=.hg/origbackups'
merging file1
creating directory: $TESTTMP/repo/.hg/origbackups
merging file2
warning: conflicts while merging file1! (edit, then use 'hg resolve --mark')
warning: conflicts while merging file2! (edit, then use 'hg resolve --mark')
[1]
$ ls .hg/origbackups
file1
file2
$ grep '<<<' file1 > /dev/null
$ grep '<<<' file2 > /dev/null
resolve <file> should re-merge file
$ echo resolved > file1
$ hg resolve -q file1
warning: conflicts while merging file1! (edit, then use 'hg resolve --mark')
[1]
$ grep '<<<' file1 > /dev/null
test .orig behavior with resolve
$ hg resolve -q file1 --tool "sh -c 'f --dump \"$TESTTMP/repo/file1.orig\"'"
$TESTTMP/repo/file1.orig:
>>>
foo
baz
<<<
resolve <file> should do nothing if 'file' was marked resolved
$ echo resolved > file1
$ hg resolve -m file1
$ hg resolve -q file1
$ cat file1
resolved
insert unsupported advisory merge record
$ hg --config extensions.fakemergerecord=$TESTDIR/fakemergerecord.py fakemergerecord -x
$ hg debugmergestate
* version 2 records
local: 57653b9f834a4493f7240b0681efcb9ae7cab745
other: dc77451844e37f03f5c559e3b8529b2b48d381d1
labels:
local: working copy
other: merge rev
unrecognized entry: x advisory record
file extras: file1 (ancestorlinknode = 99726c03216e233810a2564cbc0adfe395007eac)
file: file1 (record type "F", state "r", hash 60b27f004e454aca81b0480209cce5081ec52390)
local path: file1 (flags "")
ancestor path: file1 (node 2ed2a3912a0b24502043eae84ee4b279c18b90dd)
other path: file1 (node 6f4310b00b9a147241b071a60c28a650827fb03d)
file extras: file2 (ancestorlinknode = 99726c03216e233810a2564cbc0adfe395007eac)
file: file2 (record type "F", state "u", hash cb99b709a1978bd205ab9dfd4c5aaa1fc91c7523)
local path: file2 (flags "")
ancestor path: file2 (node 2ed2a3912a0b24502043eae84ee4b279c18b90dd)
other path: file2 (node 6f4310b00b9a147241b071a60c28a650827fb03d)
$ hg resolve -l
R file1
U file2
insert unsupported mandatory merge record
$ hg --config extensions.fakemergerecord=$TESTDIR/fakemergerecord.py fakemergerecord -X
$ hg debugmergestate
* version 2 records
local: 57653b9f834a4493f7240b0681efcb9ae7cab745
other: dc77451844e37f03f5c559e3b8529b2b48d381d1
labels:
local: working copy
other: merge rev
file extras: file1 (ancestorlinknode = 99726c03216e233810a2564cbc0adfe395007eac)
file: file1 (record type "F", state "r", hash 60b27f004e454aca81b0480209cce5081ec52390)
local path: file1 (flags "")
ancestor path: file1 (node 2ed2a3912a0b24502043eae84ee4b279c18b90dd)
other path: file1 (node 6f4310b00b9a147241b071a60c28a650827fb03d)
file extras: file2 (ancestorlinknode = 99726c03216e233810a2564cbc0adfe395007eac)
file: file2 (record type "F", state "u", hash cb99b709a1978bd205ab9dfd4c5aaa1fc91c7523)
local path: file2 (flags "")
ancestor path: file2 (node 2ed2a3912a0b24502043eae84ee4b279c18b90dd)
other path: file2 (node 6f4310b00b9a147241b071a60c28a650827fb03d)
unrecognized entry: X mandatory record
$ hg resolve -l
abort: unsupported merge state records: X
(see https://mercurial-scm.org/wiki/MergeStateRecords for more information)
[255]
$ hg resolve -ma
abort: unsupported merge state records: X
(see https://mercurial-scm.org/wiki/MergeStateRecords for more information)
[255]
$ hg summary
warning: merge state has unsupported record types: X
parent: 2:57653b9f834a
append baz to files
parent: 1:dc77451844e3
append bar to files
branch: default
commit: 2 modified, 2 unknown (merge)
update: 2 new changesets (update)
phases: 5 draft
update --clean shouldn't abort on unsupported records
$ hg up -qC 1
$ hg debugmergestate
no merge state found
test crashed merge with empty mergestate
$ mkdir .hg/merge
$ touch .hg/merge/state
resolve -l should be empty
$ hg resolve -l
$ cd ..