Add an UnusableDependencies incompatibility kind and use for conflicting versions

crates/puffin-cli/tests/pip_compile.rs

@@ -666,14 +666,16 @@ fn compile_numpy_py38() -> Result<()> {
             .arg("--no-build")
             .env("VIRTUAL_ENV", venv.as_os_str())
             .current_dir(&temp_dir), @r###"
-            success: false
-            exit_code: 2
-            ----- stdout -----
-
-            ----- stderr -----
-            error: Failed to build distribution: numpy-1.24.4.tar.gz
-              Caused by: Building source distributions is disabled
-            "###);
+        success: true
+        exit_code: 0
+        ----- stdout -----
+        # This file was autogenerated by Puffin v0.0.1 via the following command:
+        #    [BIN_PATH] pip-compile requirements.in --python-version py38 --cache-dir [CACHE_DIR]
+        numpy==1.24.4
+
+        ----- stderr -----
+        Resolved 1 package in [TIME]
+        "###);
     });
 
     Ok(())

crates/puffin-cli/tests/snapshots/pip_compile__compile_unsolvable_requirements.snap

@@ -6,15 +6,16 @@ info:
     - pip-compile
     - pyproject.toml
     - "--cache-dir"
-    - /var/folders/bc/qlsk3t6x7c9fhhbvvcg68k9c0000gp/T/.tmpN531dN
+    - /var/folders/bc/qlsk3t6x7c9fhhbvvcg68k9c0000gp/T/.tmpvGljPp
   env:
-    VIRTUAL_ENV: /var/folders/bc/qlsk3t6x7c9fhhbvvcg68k9c0000gp/T/.tmp99w9dK/.venv
+    VIRTUAL_ENV: /var/folders/bc/qlsk3t6x7c9fhhbvvcg68k9c0000gp/T/.tmp2rBXR2/.venv
 ---
 success: false
 exit_code: 1
 ----- stdout -----
 
 ----- stderr -----
   × No solution found when resolving dependencies:
-  ╰─▶ my-project depends on django∅
+  ╰─▶ my-project dependencies are unusable: `django==5.0b1` does not intersect
+      with `django==5.0a1`
 

crates/puffin-resolver/src/error.rs

@@ -44,6 +44,9 @@ pub enum ResolveError {
     #[error("Conflicting URLs for package `{0}`: {1} and {2}")]
     ConflictingUrls(PackageName, String, String),
 
+    #[error("`{0}{1}` does not intersect with `{0}{2}`")]
+    ConflictingVersions(PubGrubPackage, Range<PubGrubVersion>, Range<PubGrubVersion>),
+
     #[error("Package `{0}` attempted to resolve via URL: {1}. URL dependencies must be expressed as direct requirements or constraints. Consider adding `{0} @ {1}` to your dependencies or constraints file.")]
     DisallowedUrl(PackageName, Url),
 

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

@@ -59,7 +59,7 @@ impl PubGrubDependencies {
 
                 if let Some(entry) = dependencies.get_key_value(&package) {
                     // Merge the versions.
-                    let version = merge_versions(entry.1, &version);
+                    let version = merge_versions(&package, entry.1, &version)?;
 
                     // Merge the package.
                     if let Some(package) = merge_package(entry.0, &package)? {
@@ -107,7 +107,7 @@ impl PubGrubDependencies {
 
                 if let Some(entry) = dependencies.get_key_value(&package) {
                     // Merge the versions.
-                    let version = merge_versions(entry.1, &version);
+                    let version = merge_versions(&package, entry.1, &version)?;
 
                     // Merge the package.
                     if let Some(package) = merge_package(entry.0, &package)? {
@@ -178,10 +178,20 @@ fn to_pubgrub(
 
 /// Merge two [`PubGrubVersion`] ranges.
 fn merge_versions(
+    package: &PubGrubPackage,
     left: &Range<PubGrubVersion>,
     right: &Range<PubGrubVersion>,
-) -> Range<PubGrubVersion> {
-    left.intersection(right)
+) -> Result<Range<PubGrubVersion>, ResolveError> {
+    let result = left.intersection(right);
+    if result.is_empty() {
+        Err(ResolveError::ConflictingVersions(
+            package.clone(),
+            left.clone(),
+            right.clone(),
+        ))
+    } else {
+        Ok(result)
+    }
 }
 
 /// Merge two [`PubGrubPackage`] instances.

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

@@ -1,5 +1,6 @@
 use std::fmt;
 
+use pubgrub::package::Package;
 use pubgrub::range::Range;
 use pubgrub::report::{DerivationTree, Derived, External, Reporter};
 use pubgrub::term::Term;
@@ -345,6 +346,8 @@ enum PuffinExternal {
     NoVersions(PubGrubPackage, Range<PubGrubVersion>),
     /// Dependencies of the package are unavailable for versions in that set.
     UnavailableDependencies(PubGrubPackage, Range<PubGrubVersion>),
+    /// Dependencies of the package are unusable for versions in that set.
+    UnusableDependencies(PubGrubPackage, Range<PubGrubVersion>, Option<String>),
     /// Incompatibility coming from the dependencies of a given package.
     FromDependencyOf(
         PubGrubPackage,
@@ -362,6 +365,9 @@ impl PuffinExternal {
             External::UnavailableDependencies(p, vs) => {
                 PuffinExternal::UnavailableDependencies(p, vs)
             }
+            External::UnusableDependencies(p, vs, reason) => {
+                PuffinExternal::UnusableDependencies(p, vs, reason)
+            }
             External::FromDependencyOf(p, vs, p_dep, vs_dep) => {
                 PuffinExternal::FromDependencyOf(p, vs, p_dep, vs_dep)
             }
@@ -395,6 +401,25 @@ impl fmt::Display for PuffinExternal {
                     )
                 }
             }
+            Self::UnusableDependencies(package, set, reason) => {
+                if let Some(reason) = reason {
+                    if matches!(package, PubGrubPackage::Root(_)) {
+                        write!(f, "{package} dependencies are unusable: {reason}")
+                    } else {
+                        if set == &Range::full() {
+                            write!(f, "dependencies of {package} are unusable: {reason}")
+                        } else {
+                            write!(f, "dependencies of {package}{set} are unusable: {reason}",)
+                        }
+                    }
+                } else {
+                    if set == &Range::full() {
+                        write!(f, "dependencies of {package} are unusable")
+                    } else {
+                        write!(f, "dependencies of {package}{set} are unusable")
+                    }
+                }
+            }
             Self::FromDependencyOf(package, package_set, dependency, dependency_set) => {
                 if package_set == &Range::full() && dependency_set == &Range::full() {
                     write!(f, "{package} depends on {dependency}")

crates/puffin-resolver/src/resolver.rs

@@ -239,6 +239,14 @@ impl<'a, Context: BuildContext + Sync> Resolver<'a, Context> {
                         ));
                         continue;
                     }
+                    Dependencies::Unusable(reason) => {
+                        state.add_incompatibility(Incompatibility::unusable_dependencies(
+                            package.clone(),
+                            version.clone(),
+                            reason.clone(),
+                        ));
+                        continue;
+                    }
                     Dependencies::Known(constraints) if constraints.contains_key(package) => {
                         return Err(PubGrubError::SelfDependency {
                             package: package.clone(),
@@ -455,7 +463,11 @@ impl<'a, Context: BuildContext + Sync> Resolver<'a, Context> {
                     None,
                     None,
                     self.markers,
-                )?;
+                );
+                if let Err(err @ ResolveError::ConflictingVersions(..)) = constraints {
+                    return Ok(Dependencies::Unusable(Some(format!("{err}"))));
+                }
+                let constraints = constraints?;
 
                 for (package, version) in constraints.iter() {
                     debug!("Adding direct dependency: {package}{version}");
@@ -910,6 +922,8 @@ impl<'a> FromIterator<&'a Url> for AllowedUrls {
 enum Dependencies {
     /// Package dependencies are unavailable.
     Unknown,
+    /// Package dependencies are not usable
+    Unusable(Option<String>),
     /// Container for all available package versions.
     Known(DependencyConstraints<PubGrubPackage, Range<PubGrubVersion>>),
 }

vendor/pubgrub/src/internal/incompatibility.rs

@@ -45,6 +45,8 @@ pub enum Kind<P: Package, VS: VersionSet> {
     NoVersions(P, VS),
     /// Dependencies of the package are unavailable for versions in that range.
     UnavailableDependencies(P, VS),
+    /// Dependencies of the package are unusable for versions in that range.
+    UnusableDependencies(P, VS, Option<String>),
     /// Incompatibility coming from the dependencies of a given package.
     FromDependencyOf(P, VS, P, VS),
     /// Derived from two causes. Stores cause ids.
@@ -104,6 +106,17 @@ impl<P: Package, VS: VersionSet> Incompatibility<P, VS> {
         }
     }
 
+    /// Create an incompatibility to remember
+    /// that a package version is not selectable
+    /// because its dependencies are not usable.
+    pub fn unusable_dependencies(package: P, version: VS::V, reason: Option<String>) -> Self {
+        let set = VS::singleton(version);
+        Self {
+            package_terms: SmallMap::One([(package.clone(), Term::Positive(set.clone()))]),
+            kind: Kind::UnusableDependencies(package, set, reason),
+        }
+    }
+
     /// Build an incompatibility from a given dependency.
     pub fn from_dependency(package: P, version: VS::V, dep: (&P, &VS)) -> Self {
         let set1 = VS::singleton(version);
@@ -206,6 +219,9 @@ impl<P: Package, VS: VersionSet> Incompatibility<P, VS> {
             Kind::UnavailableDependencies(package, set) => DerivationTree::External(
                 External::UnavailableDependencies(package.clone(), set.clone()),
             ),
+            Kind::UnusableDependencies(package, set, reason) => DerivationTree::External(
+                External::UnusableDependencies(package.clone(), set.clone(), reason.clone()),
+            ),
             Kind::FromDependencyOf(package, set, dep_package, dep_set) => {
                 DerivationTree::External(External::FromDependencyOf(
                     package.clone(),

vendor/pubgrub/src/range.rs

@@ -117,6 +117,10 @@ impl<V> Range<V> {
             segments: SmallVec::one((Included(v1.into()), Excluded(v2.into()))),
         }
     }
+
+    pub fn is_empty(&self) -> bool {
+        self.segments.is_empty()
+    }
 }
 
 impl<V: Clone> Range<V> {

vendor/pubgrub/src/report.rs

@@ -41,6 +41,8 @@ pub enum External<P: Package, VS: VersionSet> {
     NoVersions(P, VS),
     /// Dependencies of the package are unavailable for versions in that set.
     UnavailableDependencies(P, VS),
+    /// Dependencies of the package are unusable for versions in that set.
+    UnusableDependencies(P, VS, Option<String>),
     /// Incompatibility coming from the dependencies of a given package.
     FromDependencyOf(P, VS, P, VS),
 }
@@ -113,6 +115,13 @@ impl<P: Package, VS: VersionSet> DerivationTree<P, VS> {
             DerivationTree::External(External::UnavailableDependencies(_, r)) => Some(
                 DerivationTree::External(External::UnavailableDependencies(package, set.union(&r))),
             ),
+            DerivationTree::External(External::UnusableDependencies(_, r, reason)) => {
+                Some(DerivationTree::External(External::UnusableDependencies(
+                    package,
+                    set.union(&r),
+                    reason,
+                )))
+            }
             DerivationTree::External(External::FromDependencyOf(p1, r1, p2, r2)) => {
                 if p1 == package {
                     Some(DerivationTree::External(External::FromDependencyOf(
@@ -158,6 +167,29 @@ impl<P: Package, VS: VersionSet> fmt::Display for External<P, VS> {
                     )
                 }
             }
+            Self::UnusableDependencies(package, set, reason) => {
+                if let Some(reason) = reason {
+                    if set == &VS::full() {
+                        write!(f, "dependencies of {} are unusable: {reason}", package)
+                    } else {
+                        write!(
+                            f,
+                            "dependencies of {} at version {} are unusable: {reason}",
+                            package, set
+                        )
+                    }
+                } else {
+                    if set == &VS::full() {
+                        write!(f, "dependencies of {} are unusable", package)
+                    } else {
+                        write!(
+                            f,
+                            "dependencies of {} at version {} are unusable",
+                            package, set
+                        )
+                    }
+                }
+            }
             Self::FromDependencyOf(p, set_p, dep, set_dep) => {
                 if set_p == &VS::full() && set_dep == &VS::full() {
                     write!(f, "{} depends on {}", p, dep)