rust/README.rst
author Gregory Szorc <gregory.szorc@gmail.com>
Sun, 03 Mar 2019 15:53:27 -0800
changeset 41859 7a1433e90482
parent 35569 964212780daf
child 44114 8a3b045d9086
permissions -rw-r--r--
inno: stop shipping pywin32 Ancient versions of Mercurial relied on pywin32 and I suspect that's why we have this dependency. We also ship the "keyring" package, which has a dependency on "pywin32-ctypes" (providing the "win32ctypes" package). This is a stripped down version of pywin32 that doesn't have as many dependencies. Since we don't have a dependency on pywin32 and since pywin32 is a bit annoying to package, let's get rid of it. With this change, py2exe no longers picks up DLL dependencies on various UCRT DLLs (because we no longer have a .pyd file beloning to pywin32 which was pulling them in). So, we were able to remove code in support of the UCRT DLLs. .. bc:: The Windows Inno installers no longer ship the pywin32 package. This package was being bundled for historical reasons. Mercurial stopped using pywin32 several years ago and the disappearance of this package should not have any meaningful impact. Differential Revision: https://phab.mercurial-scm.org/D6067

===================
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.