view tests/test-convert-splicemap.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

  $ echo "[extensions]" >> $HGRCPATH
  $ echo "convert=" >> $HGRCPATH
  $ glog()
  > {
  >     hg log -G --template '{rev}:{node|short} "{desc|firstline}"\
  >  files: {files}\n' "$@"
  > }
  $ hg init repo1
  $ cd repo1
  $ echo a > a
  $ hg ci -Am adda
  adding a
  $ echo b > b
  $ echo a >> a
  $ hg ci -Am addb
  adding b
  $ PARENTID1=`hg id --debug -i`
  $ echo c > c
  $ hg ci -Am addc
  adding c
  $ PARENTID2=`hg id --debug -i`
  $ cd ..
  $ glog -R repo1
  @  2:e55c719b85b6 "addc" files: c
  |
  o  1:6d4c2037ddc2 "addb" files: a b
  |
  o  0:07f494440405 "adda" files: a
  

  $ hg init repo2
  $ cd repo2
  $ echo b > a
  $ echo d > d
  $ hg ci -Am addaandd
  adding a
  adding d
  $ INVALIDID1=afd12345af
  $ INVALIDID2=28173x36ddd1e67bf7098d541130558ef5534a86
  $ CHILDID1=`hg id --debug -i`
  $ echo d >> d
  $ hg ci -Am changed
  $ CHILDID2=`hg id --debug -i`
  $ echo e > e
  $ hg ci -Am adde
  adding e
  $ cd ..
  $ glog -R repo2
  @  2:a39b65753b0a "adde" files: e
  |
  o  1:e4ea00df9189 "changed" files: d
  |
  o  0:527cdedf31fb "addaandd" files: a d
  

test invalid splicemap1

  $ cat > splicemap <<EOF
  > $CHILDID2
  > EOF
  $ hg convert --splicemap splicemap repo2 repo1
  abort: syntax error in splicemap(1): child parent1[,parent2] expected
  [255]

test invalid splicemap2

  $ cat > splicemap <<EOF
  > $CHILDID2 $PARENTID1, $PARENTID2, $PARENTID2
  > EOF
  $ hg convert --splicemap splicemap repo2 repo1
  abort: syntax error in splicemap(1): child parent1[,parent2] expected
  [255]

test invalid splicemap3

  $ cat > splicemap <<EOF
  > $INVALIDID1 $INVALIDID2
  > EOF
  $ hg convert --splicemap splicemap repo2 repo1
  abort: splicemap entry afd12345af is not a valid revision identifier
  [255]

splice repo2 on repo1

  $ cat > splicemap <<EOF
  > $CHILDID1 $PARENTID1
  > $CHILDID2 $PARENTID2,$CHILDID1
  > 
  > EOF
  $ cat splicemap
  527cdedf31fbd5ea708aa14eeecf53d4676f38db 6d4c2037ddc2cb2627ac3a244ecce35283268f8e
  e4ea00df91897da3079a10fab658c1eddba6617b e55c719b85b60e5102fac26110ba626e7cb6b7dc,527cdedf31fbd5ea708aa14eeecf53d4676f38db
  
  $ hg clone repo1 target1
  updating to branch default
  3 files updated, 0 files merged, 0 files removed, 0 files unresolved
  $ hg convert --splicemap splicemap repo2 target1
  scanning source...
  sorting...
  converting...
  2 addaandd
  spliced in 6d4c2037ddc2cb2627ac3a244ecce35283268f8e as parents of 527cdedf31fbd5ea708aa14eeecf53d4676f38db
  1 changed
  spliced in e55c719b85b60e5102fac26110ba626e7cb6b7dc and 527cdedf31fbd5ea708aa14eeecf53d4676f38db as parents of e4ea00df91897da3079a10fab658c1eddba6617b
  0 adde
  $ glog -R target1
  o  5:16bc847b02aa "adde" files: e
  |
  o    4:e30e4fee3418 "changed" files: d
  |\
  | o  3:e673348c3a3c "addaandd" files: a d
  | |
  @ |  2:e55c719b85b6 "addc" files: c
  |/
  o  1:6d4c2037ddc2 "addb" files: a b
  |
  o  0:07f494440405 "adda" files: a
  



Test splicemap and conversion order

  $ hg init ordered
  $ cd ordered
  $ echo a > a
  $ hg ci -Am adda
  adding a
  $ hg branch branch
  marked working directory as branch branch
  (branches are permanent and global, did you want a bookmark?)
  $ echo a >> a
  $ hg ci -Am changea
  $ echo a >> a
  $ hg ci -Am changeaagain
  $ hg up 0
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
  $ echo b > b
  $ hg ci -Am addb
  adding b

We want 2 to depend on 1 and 3. Since 3 is always converted after 2,
the bug should be exhibited with all conversion orders.

  $ cat > ../splicemap <<EOF
  > `(hg id -r 2 -i --debug)` `(hg id -r 1 -i --debug)`, `(hg id -r 3 -i --debug)`
  > EOF
  $ cd ..
  $ cat splicemap
  7c364e7fa7d70ae525610c016317ed717b519d97 717d54d67e6c31fd75ffef2ff3042bdd98418437, 102a90ea7b4a3361e4082ed620918c261189a36a

Test regular conversion

  $ hg convert --splicemap splicemap ordered ordered-hg1
  initializing destination ordered-hg1 repository
  scanning source...
  sorting...
  converting...
  3 adda
  2 changea
  1 addb
  0 changeaagain
  spliced in 717d54d67e6c31fd75ffef2ff3042bdd98418437 and 102a90ea7b4a3361e4082ed620918c261189a36a as parents of 7c364e7fa7d70ae525610c016317ed717b519d97
  $ glog -R ordered-hg1
  o    3:4cb04b9afbf2 "changeaagain" files: a
  |\
  | o  2:102a90ea7b4a "addb" files: b
  | |
  o |  1:717d54d67e6c "changea" files: a
  |/
  o  0:07f494440405 "adda" files: a
  

Test conversion with parent revisions already in dest, using source
and destination identifiers. Test unknown splicemap target.

  $ hg convert -r1 ordered ordered-hg2
  initializing destination ordered-hg2 repository
  scanning source...
  sorting...
  converting...
  1 adda
  0 changea
  $ hg convert -r3 ordered ordered-hg2
  scanning source...
  sorting...
  converting...
  0 addb
  $ cat > splicemap <<EOF
  > `(hg -R ordered id -r 2 -i --debug)` \
  > `(hg -R ordered-hg2 id -r 1 -i --debug)`,\
  > `(hg -R ordered-hg2 id -r 2 -i --debug)`
  > deadbeef102a90ea7b4a3361e4082ed620918c26 deadbeef102a90ea7b4a3361e4082ed620918c27
  > EOF
  $ hg convert --splicemap splicemap ordered ordered-hg2
  scanning source...
  splice map revision deadbeef102a90ea7b4a3361e4082ed620918c26 is not being converted, ignoring
  sorting...
  converting...
  0 changeaagain
  spliced in 717d54d67e6c31fd75ffef2ff3042bdd98418437 and 102a90ea7b4a3361e4082ed620918c261189a36a as parents of 7c364e7fa7d70ae525610c016317ed717b519d97
  $ glog -R ordered-hg2
  o    3:4cb04b9afbf2 "changeaagain" files: a
  |\
  | o  2:102a90ea7b4a "addb" files: b
  | |
  o |  1:717d54d67e6c "changea" files: a
  |/
  o  0:07f494440405 "adda" files: a
  

Test empty conversion

  $ hg convert --splicemap splicemap ordered ordered-hg2
  scanning source...
  splice map revision deadbeef102a90ea7b4a3361e4082ed620918c26 is not being converted, ignoring
  sorting...
  converting...

Test clonebranches

  $ hg --config convert.hg.clonebranches=true convert \
  >   --splicemap splicemap ordered ordered-hg3
  initializing destination ordered-hg3 repository
  scanning source...
  abort: revision 717d54d67e6c31fd75ffef2ff3042bdd98418437 not found in destination repository (lookups with clonebranches=true are not implemented)
  [255]

Test invalid dependency

  $ cat > splicemap <<EOF
  > `(hg -R ordered id -r 2 -i --debug)` \
  > deadbeef102a90ea7b4a3361e4082ed620918c26,\
  > `(hg -R ordered-hg2 id -r 2 -i --debug)`
  > EOF
  $ hg convert --splicemap splicemap ordered ordered-hg4
  initializing destination ordered-hg4 repository
  scanning source...
  abort: unknown splice map parent: deadbeef102a90ea7b4a3361e4082ed620918c26
  [255]