Surface request stream errors in the resolver (#107)

Closes https://github.com/astral-sh/puffin/issues/105.

crates/puffin-resolver/src/error.rs

@@ -10,12 +10,18 @@ pub enum ResolveError {
     #[error("Failed to find a version of {0} that satisfies the requirement")]
     NotFound(Requirement),
 
+    #[error("The request stream terminated unexpectedly")]
+    StreamTermination,
+
     #[error(transparent)]
     Client(#[from] puffin_client::PypiClientError),
 
     #[error(transparent)]
     TrySend(#[from] futures::channel::mpsc::SendError),
 
+    #[error(transparent)]
+    Join(#[from] tokio::task::JoinError),
+
     #[error(transparent)]
     PubGrub(#[from] pubgrub::error::PubGrubError<PubGrubPackage, PubGrubVersion>),
 }

crates/puffin-resolver/src/pubgrub/version.rs

@@ -7,11 +7,6 @@ use once_cell::sync::Lazy;
 pub struct PubGrubVersion(pep440_rs::Version);
 
 impl PubGrubVersion {
-    /// Returns `true` if this is a pre-release version.
-    pub fn is_prerelease(&self) -> bool {
-        self.0.pre.is_some() || self.0.dev.is_some()
-    }
-
     /// Returns the smallest PEP 440 version that is larger than `self`.
     pub fn next(&self) -> PubGrubVersion {
         let mut next = self.clone();

crates/puffin-resolver/src/resolver.rs

@@ -7,11 +7,12 @@ use std::sync::Arc;
 
 use anyhow::Result;
 use futures::future::Either;
-use futures::{StreamExt, TryFutureExt};
+use futures::{pin_mut, FutureExt, StreamExt, TryFutureExt};
 use pubgrub::error::PubGrubError;
 use pubgrub::range::Range;
 use pubgrub::solver::{DependencyConstraints, Incompatibility, State};
 use pubgrub::type_aliases::SelectedDependencies;
+use tokio::select;
 use tracing::{debug, trace};
 use waitmap::WaitMap;
 
@@ -60,7 +61,7 @@ impl<'a> Resolver<'a> {
         // A channel to fetch package metadata (e.g., given `flask`, fetch all versions) and version
         // metadata (e.g., given `flask==1.0.0`, fetch the metadata for that version).
         let (request_sink, request_stream) = futures::channel::mpsc::unbounded();
-        tokio::spawn({
+        let requests_fut = tokio::spawn({
             let cache = cache.clone();
             let client = client.clone();
             async move {
@@ -101,7 +102,7 @@ impl<'a> Resolver<'a> {
                     }
                 }
 
-                Ok::<(), anyhow::Error>(())
+                Ok::<(), ResolveError>(())
             }
         });
 
@@ -112,52 +113,39 @@ impl<'a> Resolver<'a> {
             request_sink.unbounded_send(Request::Package(package_name))?;
         }
 
-        // Track the packages and versions that we've requested.
-        let mut requested_packages = HashSet::new();
-        let mut requested_versions = HashSet::new();
-        let mut pins = HashMap::new();
+        // Run the solver.
+        let resolve_fut = self.solve(&cache, &request_sink);
 
-        let selected_dependencies = self
-            .solve(
-                &cache,
-                &mut pins,
-                &mut requested_packages,
-                &mut requested_versions,
-                &request_sink,
-            )
-            .await?;
+        let requests_fut = requests_fut.fuse();
+        let resolve_fut = resolve_fut.fuse();
+        pin_mut!(requests_fut, resolve_fut);
 
-        // Map to our own internal resolution type.
-        let mut resolution = BTreeMap::new();
-        for (package, version) in selected_dependencies {
-            let PubGrubPackage::Package(package_name, None) = package else {
-                continue;
-            };
+        let resolution = select! {
+            result = requests_fut => {
+                result??;
+                return Err(ResolveError::StreamTermination);
+            }
+            resolution = resolve_fut => {
+                resolution?
+            }
+        };
 
-            let version = pep440_rs::Version::from(version);
-            let file = pins
-                .get(&package_name)
-                .and_then(|versions| versions.get(&version))
-                .unwrap()
-                .clone();
-            let pinned_package = PinnedPackage::new(package_name.clone(), version, file);
-            resolution.insert(package_name, pinned_package);
-        }
-
-        Ok(Resolution::new(resolution))
+        Ok(resolution.into())
     }
 
     /// Run the `PubGrub` solver.
     async fn solve(
         &self,
         cache: &SolverCache,
-        pins: &mut HashMap<PackageName, HashMap<pep440_rs::Version, File>>,
-        requested_packages: &mut HashSet<PackageName>,
-        requested_versions: &mut HashSet<String>,
         request_sink: &futures::channel::mpsc::UnboundedSender<Request>,
-    ) -> Result<SelectedDependencies<PubGrubPackage, PubGrubVersion>, ResolveError> {
+    ) -> Result<PubGrubResolution, ResolveError> {
         let root = PubGrubPackage::Root;
 
+        // Keep track of the packages for which we've requested metadata.
+        let mut requested_packages = HashSet::new();
+        let mut requested_versions = HashSet::new();
+        let mut pins = HashMap::new();
+
         // Start the solve.
         let mut state = State::init(root.clone(), MIN_VERSION.clone());
         let mut added_dependencies: HashMap<PubGrubPackage, HashSet<PubGrubVersion>> =
@@ -170,11 +158,15 @@ impl<'a> Resolver<'a> {
 
             // Fetch the list of candidates.
             let Some(potential_packages) = state.partial_solution.potential_packages() else {
-                return state.partial_solution.extract_solution().ok_or_else(|| {
-                    PubGrubError::Failure(
+                let Some(selected_dependencies) = state.partial_solution.extract_solution() else {
+                    return Err(PubGrubError::Failure(
                         "How did we end up with no package to choose but no solution?".into(),
                     )
-                    .into()
+                    .into());
+                };
+                return Ok(PubGrubResolution {
+                    selected_dependencies,
+                    pins,
                 });
             };
 
@@ -184,8 +176,8 @@ impl<'a> Resolver<'a> {
                 .choose_package_version(
                     potential_packages,
                     cache,
-                    pins,
-                    requested_versions,
+                    &mut pins,
+                    &mut requested_versions,
                     request_sink,
                 )
                 .await?;
@@ -218,8 +210,8 @@ impl<'a> Resolver<'a> {
                         package,
                         &version,
                         cache,
-                        pins,
-                        requested_packages,
+                        &mut pins,
+                        &mut requested_packages,
                         request_sink,
                     )
                     .await?
@@ -516,3 +508,33 @@ enum Dependencies {
     /// Container for all available package versions.
     Known(DependencyConstraints<PubGrubPackage, PubGrubVersion>),
 }
+
+#[derive(Debug)]
+struct PubGrubResolution {
+    /// The selected dependencies.
+    selected_dependencies: SelectedDependencies<PubGrubPackage, PubGrubVersion>,
+    /// The selected file (source or built distribution) for each package.
+    pins: HashMap<PackageName, HashMap<pep440_rs::Version, File>>,
+}
+
+impl From<PubGrubResolution> for Resolution {
+    fn from(value: PubGrubResolution) -> Self {
+        let mut packages = BTreeMap::new();
+        for (package, version) in value.selected_dependencies {
+            let PubGrubPackage::Package(package_name, None) = package else {
+                continue;
+            };
+
+            let version = pep440_rs::Version::from(version);
+            let file = value
+                .pins
+                .get(&package_name)
+                .and_then(|versions| versions.get(&version))
+                .unwrap()
+                .clone();
+            let pinned_package = PinnedPackage::new(package_name.clone(), version, file);
+            packages.insert(package_name, pinned_package);
+        }
+        Resolution::new(packages)
+    }
+}