Dependency specifiers (PEP 508) in Rust
A library for python dependency specifiers, better known as PEP 508.
Usage
In Rust
use FromStr;
use Requirement;
let marker = r#"requests [security,tests] >= 2.8.1, == 2.8.* ; python_version > "3.8""#;
let dependency_specification = from_str.unwrap;
assert_eq!;
assert_eq!;
In Python
=
assert ==
assert ==
assert ==
Python bindings are built with maturin, but you can also use the normal pip install .
Version
and VersionSpecifier
from pep440_rs are reexported to avoid type mismatches.
Markers
Markers allow you to install dependencies only in specific environments (python version, operating system, architecture, etc.) or when a specific feature is activated. E.g. you can say importlib-metadata ; python_version < "3.8"
or itsdangerous (>=1.1.0) ; extra == 'security'
. Unfortunately, the marker grammar has some oversights (e.g. https://github.com/pypa/packaging.python.org/pull/1181) and the design of comparisons (PEP 440 comparisons with lexicographic fallback) leads to confusing outcomes. This implementation tries to carefully validate everything and emit warnings whenever bogus comparisons with unintended semantics are made.
In python, warnings are by default sent to the normal python logging infrastructure:
=
assert not
assert
assert not
assert
=
# This will log:
# "Expected PEP 440 version to compare with python_version, found '3.9.', "
# "evaluating to false: Version `3.9.` doesn't match PEP 440 rules"