471a1d657d
## Summary This PR enables the proof-of-concept resolver to backtrack by way of using the `pubgrub-rs` crate. Rather than using PubGrub as a _framework_ (implementing the `DependencyProvider` trait, letting PubGrub call us), I've instead copied over PubGrub's primary solver hook (which is only ~100 lines or so) and modified it for our purposes (e.g., made it async). There's a lot to improve here, but it's a start that will let us understand PubGrub's appropriateness for this problem space. A few observations: - In simple cases, the resolver is slower than our current (naive) resolver. I think it's just that the pipelining isn't as efficient as in the naive case, where we can just stream package and version fetches concurrently without any bottlenecks. - A lot of the code here relates to bridging PubGrub with our own abstractions -- so we need a `PubGrubPackage`, a `PubGrubVersion`, etc. |
||
|---|---|---|
| .. | ||
| src | ||
| Cargo.lock | ||
| Cargo.toml | ||
| License-Apache | ||
| License-BSD | ||
| Readme.md | ||
Dependency specifiers (PEP 508) in Rust
A library for python dependency specifiers, better known as PEP 508.
Usage
In Rust
use std::str::FromStr;
use pep508_rs::Requirement;
let marker = r#"requests [security,tests] >= 2.8.1, == 2.8.* ; python_version > "3.8""#;
let dependency_specification = Requirement::from_str(marker).unwrap();
assert_eq!(dependency_specification.name, "requests");
assert_eq!(dependency_specification.extras, Some(vec!["security".to_string(), "tests".to_string()]));
In Python
from pep508_rs import Requirement
requests = Requirement(
'requests [security,tests] >= 2.8.1, == 2.8.* ; python_version > "3.8"'
)
assert requests.name == "requests"
assert requests.extras == ["security", "tests"]
assert [str(i) for i in requests.version_or_url] == [">= 2.8.1", "== 2.8.*"]
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:
from pep508_rs import Requirement, MarkerEnvironment
env = MarkerEnvironment.current()
assert not Requirement("numpy; extra == 'science'").evaluate_markers(env, [])
assert Requirement("numpy; extra == 'science'").evaluate_markers(env, ["science"])
assert not Requirement(
"numpy; extra == 'science' and extra == 'arrays'"
).evaluate_markers(env, ["science"])
assert Requirement(
"numpy; extra == 'science' or extra == 'arrays'"
).evaluate_markers(env, ["science"])
from pep508_rs import Requirement, MarkerEnvironment
env = MarkerEnvironment.current()
Requirement("numpy; python_version >= '3.9.'").evaluate_markers(env, [])
# 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"