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debug: move extensions debug behind a dedicated flag...
debug: move extensions debug behind a dedicated flag Since b86664c81833, we process the `--debug` flag earlier. This is overall good and useful, but has at least one negative side effect. Previously the debug message we report when trying to import extensions were issued before we processed the `--debug` flag. Now they happen after. Before: $ ./hg id --debug 21f507b8de2f9c1606e9aeb5ec7d2a6dedb7a4a7 tip After: $ ./hg id --debug ☿ (revset-bench) could not import hgext.evolve (No module named evolve): trying hgext3rd.evolve could not import hgext.mercurial_keyring (No module named mercurial_keyring): trying hgext3rd.mercurial_keyring could not import hgext3rd.mercurial_keyring (No module named mercurial_keyring): trying mercurial_keyring could not import hgext.hggit (No module named hggit): trying hgext3rd.hggit could not import hgext3rd.hggit (No module named hggit): trying hggit 21f507b8de2f9c1606e9aeb5ec7d2a6dedb7a4a7 tip (This get worse if --traceback is used). To work around this, we move this extensions related debug message behind a new flag 'devel.debug.extensions' and restore the previous output. I'm not fully happy about using the 'devel' section for a flag that can be used by legitimate users to debug extensions issues. However, it fits well next to other `devel.devel.*` options and is mostly used by extensions author anyway. We might move it to another, more appropriate section in the future (using alias).
Boris Feld -
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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.