make `ErrorTree` for `NoSolutionError` externally accessible (#14444)

Hey, are you okay with exposing the `ErrorTree` for library consumers?

We have a use case that needs more information on conflicts. We need the
tree-structure of the conflict and be able to traverse it in particular.

Signed-off-by: Simon Sure <ssure@palantir.com>

crates/uv-resolver/src/error.rs

@@ -156,7 +156,7 @@ impl<T> From<tokio::sync::mpsc::error::SendError<T>> for ResolveError {
     }
 }
 
-pub(crate) type ErrorTree = DerivationTree<PubGrubPackage, Range<Version>, UnavailableReason>;
+pub type ErrorTree = DerivationTree<PubGrubPackage, Range<Version>, UnavailableReason>;
 
 /// A wrapper around [`pubgrub::error::NoSolutionError`] that displays a resolution failure report.
 pub struct NoSolutionError {
@@ -367,6 +367,11 @@ impl NoSolutionError {
         NoSolutionHeader::new(self.env.clone())
     }
 
+    /// Get the conflict derivation tree for external analysis
+    pub fn derivation_tree(&self) -> &ErrorTree {
+        &self.error
+    }
+
     /// Hint at limiting the resolver environment if universal resolution failed for a target
     /// that is not the current platform or not the current Python version.
     fn hint_disjoint_targets(&self, f: &mut Formatter) -> std::fmt::Result {

crates/uv-resolver/src/lib.rs

@@ -1,5 +1,5 @@
 pub use dependency_mode::DependencyMode;
-pub use error::{NoSolutionError, NoSolutionHeader, ResolveError, SentinelRange};
+pub use error::{ErrorTree, NoSolutionError, NoSolutionHeader, ResolveError, SentinelRange};
 pub use exclude_newer::ExcludeNewer;
 pub use exclusions::Exclusions;
 pub use flat_index::{FlatDistributions, FlatIndex};
@@ -54,7 +54,7 @@ mod options;
 mod pins;
 mod preferences;
 mod prerelease;
-mod pubgrub;
+pub mod pubgrub;
 mod python_requirement;
 mod redirect;
 mod resolution;

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

@@ -1,6 +1,6 @@
 pub(crate) use crate::pubgrub::dependencies::PubGrubDependency;
 pub(crate) use crate::pubgrub::distribution::PubGrubDistribution;
-pub(crate) use crate::pubgrub::package::{PubGrubPackage, PubGrubPackageInner, PubGrubPython};
+pub use crate::pubgrub::package::{PubGrubPackage, PubGrubPackageInner, PubGrubPython};
 pub(crate) use crate::pubgrub::priority::{PubGrubPriorities, PubGrubPriority, PubGrubTiebreaker};
 pub(crate) use crate::pubgrub::report::PubGrubReportFormatter;
 

crates/uv-resolver/src/pubgrub/package.rs

@@ -9,7 +9,7 @@ use crate::python_requirement::PythonRequirement;
 
 /// [`Arc`] wrapper around [`PubGrubPackageInner`] to make cloning (inside PubGrub) cheap.
 #[derive(Debug, Clone, Eq, Hash, PartialEq, PartialOrd, Ord)]
-pub(crate) struct PubGrubPackage(Arc<PubGrubPackageInner>);
+pub struct PubGrubPackage(Arc<PubGrubPackageInner>);
 
 impl Deref for PubGrubPackage {
     type Target = PubGrubPackageInner;
@@ -39,7 +39,7 @@ impl From<PubGrubPackageInner> for PubGrubPackage {
 ///    package (e.g., `black[colorama]`), and mark it as a dependency of the real package (e.g.,
 ///    `black`). We then discard the virtual packages at the end of the resolution process.
 #[derive(Debug, Clone, Eq, Hash, PartialEq, PartialOrd, Ord)]
-pub(crate) enum PubGrubPackageInner {
+pub enum PubGrubPackageInner {
     /// The root package, which is used to start the resolution process.
     Root(Option<PackageName>),
     /// A Python version.
@@ -295,7 +295,7 @@ impl PubGrubPackage {
 }
 
 #[derive(Debug, Copy, Clone, Eq, PartialEq, PartialOrd, Hash, Ord)]
-pub(crate) enum PubGrubPython {
+pub enum PubGrubPython {
     /// The Python version installed in the current environment.
     Installed,
     /// The Python version for which dependencies are being resolved.

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

@@ -7,7 +7,7 @@ use uv_platform_tags::{AbiTag, Tags};
 
 /// The reason why a package or a version cannot be used.
 #[derive(Debug, Clone, Eq, PartialEq)]
-pub(crate) enum UnavailableReason {
+pub enum UnavailableReason {
     /// The entire package cannot be used.
     Package(UnavailablePackage),
     /// A single version cannot be used.
@@ -29,7 +29,7 @@ impl Display for UnavailableReason {
 /// Most variant are from [`MetadataResponse`] without the error source, since we don't format
 /// the source and we want to merge unavailable messages across versions.
 #[derive(Debug, Clone, Eq, PartialEq)]
-pub(crate) enum UnavailableVersion {
+pub enum UnavailableVersion {
     /// Version is incompatible because it has no usable distributions
     IncompatibleDist(IncompatibleDist),
     /// The wheel metadata was found, but could not be parsed.
@@ -123,7 +123,7 @@ impl From<&MetadataUnavailable> for UnavailableVersion {
 
 /// The package is unavailable and cannot be used.
 #[derive(Debug, Clone, Eq, PartialEq)]
-pub(crate) enum UnavailablePackage {
+pub enum UnavailablePackage {
     /// Index lookups were disabled (i.e., `--no-index`) and the package was not found in a flat index (i.e. from `--find-links`).
     NoIndex,
     /// Network requests were disabled (i.e., `--offline`), and the package was not found in the cache.