make universal resolver fork only when markers are disjoint (#4135)

The basic idea here is to make it so forking can only ever result in a
resolution that, for a particular marker environment, will only install
at most one version of a package. We can guarantee this by ensuring we
only fork on conflicting dependency specifications only when their
corresponding markers are completely disjoint. If they aren't, then
resolution _must_ find a single version of the package in the
intersection of the two dependency specifications.

A test for this case has been added to packse here:
astral-sh/packse#182. Previously, that test
would result in a resolution with two different unconditional versions
of the same package. With this change, resolution fails (as it should).

A commit-by-commit review should be helpful here, since the first commit
is a refactor to make the second commit a bit more digestible.

crates/uv/tests/common/mod.rs

@@ -26,7 +26,7 @@ pub static EXCLUDE_NEWER: &str = "2024-03-25T00:00:00Z";
 /// Using a find links url allows using `--index-url` instead of `--extra-index-url` in tests
 /// to prevent dependency confusion attacks against our test suite.
 pub const BUILD_VENDOR_LINKS_URL: &str =
-    "https://raw.githubusercontent.com/astral-sh/packse/0.3.17/vendor/links.html";
+    "https://raw.githubusercontent.com/astral-sh/packse/0.3.18/vendor/links.html";
 
 #[doc(hidden)] // Macro and test context only, don't use directly.
 pub const INSTA_FILTERS: &[(&str, &str)] = &[

crates/uv/tests/pip_compile_scenarios.rs

@@ -1,7 +1,7 @@
 //! DO NOT EDIT
 //!
 //! Generated with `./scripts/sync_scenarios.sh`
-//! Scenarios from <https://github.com/astral-sh/packse/tree/0.3.17/scenarios>
+//! Scenarios from <https://github.com/astral-sh/packse/tree/0.3.18/scenarios>
 //!
 #![cfg(all(feature = "python", feature = "pypi", unix))]
 
@@ -27,9 +27,9 @@ fn command(context: &TestContext, python_versions: &[&str]) -> Command {
         .arg("compile")
         .arg("requirements.in")
         .arg("--index-url")
-        .arg("https://astral-sh.github.io/packse/0.3.17/simple-html/")
+        .arg("https://astral-sh.github.io/packse/0.3.18/simple-html/")
         .arg("--find-links")
-        .arg("https://raw.githubusercontent.com/astral-sh/packse/0.3.17/vendor/links.html")
+        .arg("https://raw.githubusercontent.com/astral-sh/packse/0.3.18/vendor/links.html")
         .arg("--cache-dir")
         .arg(context.cache_dir.path())
         .env("VIRTUAL_ENV", context.venv.as_os_str())

crates/uv/tests/pip_install_scenarios.rs

@@ -1,7 +1,7 @@
 //! DO NOT EDIT
 //!
 //! Generated with `./scripts/sync_scenarios.sh`
-//! Scenarios from <https://github.com/astral-sh/packse/tree/0.3.17/scenarios>
+//! Scenarios from <https://github.com/astral-sh/packse/tree/0.3.18/scenarios>
 //!
 #![cfg(all(feature = "python", feature = "pypi", unix))]
 
@@ -46,9 +46,9 @@ fn command(context: &TestContext) -> Command {
         .arg("pip")
         .arg("install")
         .arg("--index-url")
-        .arg("https://astral-sh.github.io/packse/0.3.17/simple-html/")
+        .arg("https://astral-sh.github.io/packse/0.3.18/simple-html/")
         .arg("--find-links")
-        .arg("https://raw.githubusercontent.com/astral-sh/packse/0.3.17/vendor/links.html")
+        .arg("https://raw.githubusercontent.com/astral-sh/packse/0.3.18/vendor/links.html")
         .arg("--cache-dir")
         .arg(context.cache_dir.path())
         .env("VIRTUAL_ENV", context.venv.as_os_str())

scripts/scenarios/requirements.in

@@ -1,2 +1,2 @@
 chevron-blue
-packse>=0.3.17
+packse>=0.3.18

scripts/scenarios/requirements.txt

@@ -46,7 +46,7 @@ nh3==0.2.17
     # via readme-renderer
 packaging==24.0
     # via hatchling
-packse==0.3.17
+packse==0.3.18
     # via -r scripts/scenarios/requirements.in
 pathspec==0.12.1
     # via hatchling