view rust/README.rst @ 43678:52e4bfebc4ba

setup: conditionalize access to `sys.dllhandle` when building extensions

This code is only run on Windows, and was crashing PyOxidizer when running in
`setup-py-install` mode.  Now an oxidized binary can be built by simply pointing
to setup.py.

Something is slightly different now that it's not being built from a virtualenv.
Previously, `hg version` could print to the screen, but now it aborts saying
"Incorrect function".  But I can see the output if redirected to a file, and
it's not complaining about missing C extensions, so I think those are loading
now (unlike from the virtualenv).  The interesting this about this incorrect
function output is that it failed when initially built.  I then went back and
did a `make clean` and `make local` with py3 and then py2 to ensure I didn't
break the existing code.  At that point I ran the oxidized executable again and
it was able to print to the screen normally!  So I ran `pyoxidizer build` again,
it only output the following, and then running the executable failed to output
again:

    (pyO2_venv) C:\Users\Matt\hg3\hg_pyO2>pyoxidizer build
        Finished dev [unoptimized + debuginfo] target(s) in 0.12s
    packaging application into C:/Users/Matt/hg3/hg_pyO2\build\apps\hg_pyO2\x86_64-pc-windows-msvc\debug
    purging C:/Users/Matt/hg3/hg_pyO2\build\apps\hg_pyO2\x86_64-pc-windows-msvc\debug
    copying C:/Users/Matt/hg3/hg_pyO2\build\target\x86_64-pc-windows-msvc\debug\hg_pyO2.exe to
        C:/Users/Matt/hg3/hg_pyO2\build\apps\hg_pyO2\x86_64-pc-windows-msvc\debug\hg_pyO2.exe
    resolving packaging state...
    writing license for [...]
    hg_pyO2 packaged into C:/Users/Matt/hg3/hg_pyO2\build\apps\hg_pyO2\x86_64-pc-windows-msvc\debug
    executable path: C:/Users/Matt/hg3/hg_pyO2\build\apps\hg_pyO2\x86_64-pc-windows-msvc\debug\hg_pyO2.exe

Differential Revision: https://phab.mercurial-scm.org/D7444

===================
Mercurial Rust Code
===================

This directory contains various Rust code for the Mercurial project.

The top-level ``Cargo.toml`` file defines a workspace containing
all primary Mercurial crates.

Building
========

To build the Rust components::

   $ cargo build

If you prefer a non-debug / release configuration::

   $ cargo build --release

Features
--------

The following Cargo features are available:

localdev (default)
   Produce files that work with an in-source-tree build.

   In this mode, the build finds and uses a ``python2.7`` binary from
   ``PATH``. The ``hg`` binary assumes it runs from ``rust/target/<target>hg``
   and it finds Mercurial files at ``dirname($0)/../../../``.

Build Mechanism
---------------

The produced ``hg`` binary is *bound* to a CPython installation. The
binary links against and loads a CPython library that is discovered
at build time (by a ``build.rs`` Cargo build script). The Python
standard library defined by this CPython installation is also used.

Finding the appropriate CPython installation to use is done by
the ``python27-sys`` crate's ``build.rs``. Its search order is::

1. ``PYTHON_SYS_EXECUTABLE`` environment variable.
2. ``python`` executable on ``PATH``
3. ``python2`` executable on ``PATH``
4. ``python2.7`` executable on ``PATH``

Additional verification of the found Python will be performed by our
``build.rs`` to ensure it meets Mercurial's requirements.

Details about the build-time configured Python are built into the
produced ``hg`` binary. This means that a built ``hg`` binary is only
suitable for a specific, well-defined role. These roles are controlled
by Cargo features (see above).

Running
=======

The ``hgcli`` crate produces an ``hg`` binary. You can run this binary
via ``cargo run``::

   $ cargo run --manifest-path hgcli/Cargo.toml

Or directly::

   $ target/debug/hg
   $ target/release/hg

You can also run the test harness with this binary::

   $ ./run-tests.py --with-hg ../rust/target/debug/hg

.. note::

   Integration with the test harness is still preliminary. Remember to
   ``cargo build`` after changes because the test harness doesn't yet
   automatically build Rust code.