view rust/README.rst @ 43385:6469c23a40a2 stable

fsmonitor: refresh pywatchman with upstream

This commit vendors pywatchman commit 259dc66dc9591f9b7ce76d0275bb1065f390c9b1
from upstream without modifications. The previously vendored pywatchman
from changeset 16f4b341288d was from Git commit c77452.

This commit effectively undoes the following Mercurial changesets:

* dd35abc409ee fsmonitor: correct an error message
* b1f62cd39b5c fsmonitor: layer on another hack in bser.c for os.stat()
  compat (issue5811)
* c31ce080eb75 py3: convert arguments, cwd and env to native strings when
  spawning subprocess
* 876494fd967d cleanup: delete lots of unused local variables
* 57264906a996 watchman: add the possibility to set the exact watchman
  binary location

The newly-vendored code has support for specifying the binary location,
so 57264906a996 does not need applied. But we do need to modify our
code to specify a proper argument name.

876494fd967d is not important, so it will be ignored.

c31ce080eb75 globally changed the code base to always pass
str to subprocess. But pywatchman's code is Python 3 clean, so
we don't need to do this.

This leaves dd35abc409ee and b1f62cd39b5c, which will be re-applied in
subsequent commits.

Differential Revision: https://phab.mercurial-scm.org/D7201

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