Fix handling of pre-releases in preferences (#14498)

Closes https://github.com/astral-sh/uv/issues/14485

I tested this using the reproduction in the issue. It'd be nice to add
test coverage though.

crates/uv-resolver/src/candidate_selector.rs

@@ -13,10 +13,9 @@ use uv_normalize::PackageName;
 use uv_pep440::Version;
 use uv_types::InstalledPackagesProvider;
 
-use crate::preferences::{Entry, Preferences};
+use crate::preferences::{Entry, PreferenceSource, Preferences};
 use crate::prerelease::{AllowPrerelease, PrereleaseStrategy};
 use crate::resolution_mode::ResolutionStrategy;
-use crate::universal_marker::UniversalMarker;
 use crate::version_map::{VersionMap, VersionMapDistHandle};
 use crate::{Exclusions, Manifest, Options, ResolverEnvironment};
 
@@ -188,7 +187,7 @@ impl CandidateSelector {
                 if index.is_some_and(|index| !entry.index().matches(index)) {
                     return None;
                 }
-                Either::Left(std::iter::once((entry.marker(), entry.pin().version())))
+                Either::Left(std::iter::once((entry.pin().version(), entry.source())))
             }
             [..] => {
                 type Entries<'a> = SmallVec<[&'a Entry; 3]>;
@@ -219,7 +218,7 @@ impl CandidateSelector {
                 Either::Right(
                     preferences
                         .into_iter()
-                        .map(|entry| (entry.marker(), entry.pin().version())),
+                        .map(|entry| (entry.pin().version(), entry.source())),
                 )
             }
         };
@@ -238,7 +237,7 @@ impl CandidateSelector {
     /// Return the first preference that satisfies the current range and is allowed.
     fn get_preferred_from_iter<'a, InstalledPackages: InstalledPackagesProvider>(
         &'a self,
-        preferences: impl Iterator<Item = (&'a UniversalMarker, &'a Version)>,
+        preferences: impl Iterator<Item = (&'a Version, PreferenceSource)>,
         package_name: &'a PackageName,
         range: &Range<Version>,
         version_maps: &'a [VersionMap],
@@ -246,7 +245,7 @@ impl CandidateSelector {
         reinstall: bool,
         env: &ResolverEnvironment,
     ) -> Option<Candidate<'a>> {
-        for (marker, version) in preferences {
+        for (version, source) in preferences {
             // Respect the version range for this requirement.
             if !range.contains(version) {
                 continue;
@@ -290,9 +289,14 @@ impl CandidateSelector {
                 let allow = match self.prerelease_strategy.allows(package_name, env) {
                     AllowPrerelease::Yes => true,
                     AllowPrerelease::No => false,
-                    // If the pre-release is "global" (i.e., provided via a lockfile, rather than
-                    // a fork), accept it unless pre-releases are completely banned.
-                    AllowPrerelease::IfNecessary => marker.is_true(),
+                    // If the pre-release was provided via an existing file, rather than from the
+                    // current solve, accept it unless pre-releases are completely banned.
+                    AllowPrerelease::IfNecessary => match source {
+                        PreferenceSource::Resolver => false,
+                        PreferenceSource::Lock
+                        | PreferenceSource::Environment
+                        | PreferenceSource::RequirementsTxt => true,
+                    },
                 };
                 if !allow {
                     continue;

crates/uv-resolver/src/preferences.rs

@@ -34,6 +34,8 @@ pub struct Preference {
     /// is part of, otherwise `None`.
     fork_markers: Vec<UniversalMarker>,
     hashes: HashDigests,
+    /// The source of the preference.
+    source: PreferenceSource,
 }
 
 impl Preference {
@@ -73,6 +75,7 @@ impl Preference {
                 .map(String::as_str)
                 .map(HashDigest::from_str)
                 .collect::<Result<_, _>>()?,
+            source: PreferenceSource::RequirementsTxt,
         }))
     }
 
@@ -91,6 +94,7 @@ impl Preference {
             index: PreferenceIndex::from(package.index(install_path)?),
             fork_markers: package.fork_markers().to_vec(),
             hashes: HashDigests::empty(),
+            source: PreferenceSource::Lock,
         }))
     }
 
@@ -112,6 +116,7 @@ impl Preference {
             // `pylock.toml` doesn't have fork annotations.
             fork_markers: vec![],
             hashes: HashDigests::empty(),
+            source: PreferenceSource::Lock,
         }))
     }
 
@@ -127,6 +132,7 @@ impl Preference {
             index: PreferenceIndex::Any,
             fork_markers: vec![],
             hashes: HashDigests::empty(),
+            source: PreferenceSource::Environment,
         })
     }
 
@@ -171,11 +177,24 @@ impl From<Option<IndexUrl>> for PreferenceIndex {
     }
 }
 
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+pub(crate) enum PreferenceSource {
+    /// The preference is from an installed package in the environment.
+    Environment,
+    /// The preference is from a `uv.ock` file.
+    Lock,
+    /// The preference is from a `requirements.txt` file.
+    RequirementsTxt,
+    /// The preference is from the current solve.
+    Resolver,
+}
+
 #[derive(Debug, Clone)]
 pub(crate) struct Entry {
     marker: UniversalMarker,
     index: PreferenceIndex,
     pin: Pin,
+    source: PreferenceSource,
 }
 
 impl Entry {
@@ -193,6 +212,11 @@ impl Entry {
     pub(crate) fn pin(&self) -> &Pin {
         &self.pin
     }
+
+    /// Return the source of the entry.
+    pub(crate) fn source(&self) -> PreferenceSource {
+        self.source
+    }
 }
 
 /// A set of pinned packages that should be preserved during resolution, if possible.
@@ -245,6 +269,7 @@ impl Preferences {
                         version: preference.version,
                         hashes: preference.hashes,
                     },
+                    source: preference.source,
                 });
             } else {
                 for fork_marker in preference.fork_markers {
@@ -255,6 +280,7 @@ impl Preferences {
                             version: preference.version.clone(),
                             hashes: preference.hashes.clone(),
                         },
+                        source: preference.source,
                     });
                 }
             }
@@ -270,11 +296,13 @@ impl Preferences {
         index: Option<IndexUrl>,
         markers: UniversalMarker,
         pin: impl Into<Pin>,
+        source: PreferenceSource,
     ) {
         self.0.entry(package_name).or_default().push(Entry {
             marker: markers,
             index: PreferenceIndex::from(index),
             pin: pin.into(),
+            source,
         });
     }
 

crates/uv-resolver/src/resolver/mod.rs

@@ -47,7 +47,7 @@ use crate::fork_strategy::ForkStrategy;
 use crate::fork_urls::ForkUrls;
 use crate::manifest::Manifest;
 use crate::pins::FilePins;
-use crate::preferences::Preferences;
+use crate::preferences::{PreferenceSource, Preferences};
 use crate::pubgrub::{
     PubGrubDependency, PubGrubDistribution, PubGrubPackage, PubGrubPackageInner, PubGrubPriorities,
     PubGrubPython,
@@ -447,6 +447,7 @@ impl<InstalledPackages: InstalledPackagesProvider> ResolverState<InstalledPackag
                                             .try_universal_markers()
                                             .unwrap_or(UniversalMarker::TRUE),
                                         version.clone(),
+                                        PreferenceSource::Resolver,
                                     );
                                 }
                             }

crates/uv/src/commands/project/lock.rs

@@ -933,7 +933,7 @@ impl ValidatedLock {
                 lock.prerelease_mode().cyan(),
                 options.prerelease_mode.cyan()
             );
-            return Ok(Self::Unusable(lock));
+            return Ok(Self::Preferable(lock));
         }
         if lock.fork_strategy() != options.fork_strategy {
             let _ = writeln!(

crates/uv/src/commands/project/mod.rs

@@ -1730,7 +1730,7 @@ pub(crate) async fn resolve_names(
 }
 
 #[derive(Debug, Clone)]
-pub(crate) enum PreferenceSource<'lock> {
+pub(crate) enum PreferenceLocation<'lock> {
     /// The preferences should be extracted from a lockfile.
     Lock {
         lock: &'lock Lock,
@@ -1745,7 +1745,7 @@ pub(crate) struct EnvironmentSpecification<'lock> {
     /// The requirements to include in the environment.
     requirements: RequirementsSpecification,
     /// The preferences to respect when resolving.
-    preferences: Option<PreferenceSource<'lock>>,
+    preferences: Option<PreferenceLocation<'lock>>,
 }
 
 impl From<RequirementsSpecification> for EnvironmentSpecification<'_> {
@@ -1758,9 +1758,9 @@ impl From<RequirementsSpecification> for EnvironmentSpecification<'_> {
 }
 
 impl<'lock> EnvironmentSpecification<'lock> {
-    /// Set the [`PreferenceSource`] for the specification.
+    /// Set the [`PreferenceLocation`] for the specification.
     #[must_use]
-    pub(crate) fn with_preferences(self, preferences: PreferenceSource<'lock>) -> Self {
+    pub(crate) fn with_preferences(self, preferences: PreferenceLocation<'lock>) -> Self {
         Self {
             preferences: Some(preferences),
             ..self
@@ -1869,7 +1869,7 @@ pub(crate) async fn resolve_environment(
 
     // If an existing lockfile exists, build up a set of preferences.
     let preferences = match spec.preferences {
-        Some(PreferenceSource::Lock { lock, install_path }) => {
+        Some(PreferenceLocation::Lock { lock, install_path }) => {
             let LockedRequirements { preferences, git } =
                 read_lock_requirements(lock, install_path, &upgrade)?;
 
@@ -1881,7 +1881,7 @@ pub(crate) async fn resolve_environment(
 
             preferences
         }
-        Some(PreferenceSource::Entries(entries)) => entries,
+        Some(PreferenceLocation::Entries(entries)) => entries,
         None => vec![],
     };
 

crates/uv/src/commands/project/run.rs

@@ -49,7 +49,7 @@ use crate::commands::project::install_target::InstallTarget;
 use crate::commands::project::lock::LockMode;
 use crate::commands::project::lock_target::LockTarget;
 use crate::commands::project::{
-    EnvironmentSpecification, PreferenceSource, ProjectEnvironment, ProjectError,
+    EnvironmentSpecification, PreferenceLocation, ProjectEnvironment, ProjectError,
     ScriptEnvironment, ScriptInterpreter, UniversalState, WorkspacePython,
     default_dependency_groups, script_specification, update_environment,
     validate_project_requires_python,
@@ -958,10 +958,10 @@ hint: If you are running a script with `{}` in the shebang, you may need to incl
             let spec = EnvironmentSpecification::from(spec).with_preferences(
                 if let Some((lock, install_path)) = base_lock.as_ref() {
                     // If we have a lockfile, use the locked versions as preferences.
-                    PreferenceSource::Lock { lock, install_path }
+                    PreferenceLocation::Lock { lock, install_path }
                 } else {
                     // Otherwise, extract preferences from the base environment.
-                    PreferenceSource::Entries(
+                    PreferenceLocation::Entries(
                         base_site_packages
                             .iter()
                             .filter_map(Preference::from_installed)