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:
- PYTHON_SYS_EXECUTABLE environment variable.
- python executable on PATH
- python2 executable on PATH
- 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.