Specialize range operations for better performance

.github/workflows/permaref.yaml

@@ -0,0 +1,40 @@
+# Automatically creates a tag for each commit to `main` so when we rebase
+# changes on top of the upstream, we retain permanent references to each
+# previous commit so they are not orphaned and eventually deleted.
+name: Create permanent reference
+
+on:
+  push:
+    branches:
+      - "main"
+
+jobs:
+  create-permaref:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v4
+
+      - name: Get the permanent ref number
+        id: get_version
+        run: |
+          # Enable pipefail so git command failures do not result in null versions downstream
+          set -x
+
+          echo "LAST_PERMA_NUMBER=$(\
+            git ls-remote --tags --refs --sort="v:refname" \
+            https://github.com/zanieb/pubgrub.git | grep "tags/perma-" | tail -n1 | sed 's/.*\/perma-//' \
+          )" >> $GITHUB_OUTPUT
+
+      - name: Configure Git
+        run: |
+          git config user.name "$GITHUB_ACTOR"
+          git config user.email "[email protected]"
+
+      - name: Create and push the new tag
+        run: |
+          TAG="perma-$((LAST_PERMA_NUMBER + 1))"
+          git tag -a "$TAG" -m 'Automatically created on push to `main`'
+          git push origin "$TAG"
+        env:
+          LAST_PERMA_NUMBER: ${{ steps.get_version.outputs.LAST_PERMA_NUMBER }}

examples/unsat_root_message_no_version.rs

@@ -2,7 +2,7 @@
 
 use pubgrub::error::PubGrubError;
 use pubgrub::range::Range;
-use pubgrub::report::Reporter;
+use pubgrub::report::{Derived, Reporter};
 use pubgrub::solver::{resolve, OfflineDependencyProvider};
 use pubgrub::version::SemanticVersion;
 
@@ -66,18 +66,18 @@ impl ReportFormatter<Package, Range<SemanticVersion>> for CustomReportFormatter
             External::NotRoot(package, version) => {
                 format!("we are solving dependencies of {package} {version}")
             }
-            External::NoVersions(package, set) => {
+            External::NoVersions(package, set, _) => {
                 if set == &Range::full() {
                     format!("there is no available version for {package}")
                 } else {
                     format!("there is no version of {package} in {set}")
                 }
             }
-            External::UnavailableDependencies(package, set) => {
+            External::Unavailable(package, set, reason) => {
                 if set == &Range::full() {
-                    format!("dependencies of {package} are unavailable")
+                    format!("dependencies of {package} are unavailable because {reason}")
                 } else {
-                    format!("dependencies of {package} at version {set} are unavailable")
+                    format!("dependencies of {package} at version {set} are unavailable because {reason}")
                 }
             }
             External::FromDependencyOf(package, package_set, dependency, dependency_set) => {
@@ -101,6 +101,105 @@ impl ReportFormatter<Package, Range<SemanticVersion>> for CustomReportFormatter
             }
         }
     }
+
+    /// Simplest case, we just combine two external incompatibilities.
+    fn explain_both_external(
+        &self,
+        external1: &External<Package, Range<SemanticVersion>>,
+        external2: &External<Package, Range<SemanticVersion>>,
+        current_terms: &Map<Package, Term<Range<SemanticVersion>>>,
+    ) -> String {
+        // TODO: order should be chosen to make it more logical.
+        format!(
+            "Because {} and {}, {}.",
+            self.format_external(external1),
+            self.format_external(external2),
+            self.format_terms(current_terms)
+        )
+    }
+
+    /// Both causes have already been explained so we use their refs.
+    fn explain_both_ref(
+        &self,
+        ref_id1: usize,
+        derived1: &Derived<Package, Range<SemanticVersion>>,
+        ref_id2: usize,
+        derived2: &Derived<Package, Range<SemanticVersion>>,
+        current_terms: &Map<Package, Term<Range<SemanticVersion>>>,
+    ) -> String {
+        // TODO: order should be chosen to make it more logical.
+        format!(
+            "Because {} ({}) and {} ({}), {}.",
+            self.format_terms(&derived1.terms),
+            ref_id1,
+            self.format_terms(&derived2.terms),
+            ref_id2,
+            self.format_terms(current_terms)
+        )
+    }
+
+    /// One cause is derived (already explained so one-line),
+    /// the other is a one-line external cause,
+    /// and finally we conclude with the current incompatibility.
+    fn explain_ref_and_external(
+        &self,
+        ref_id: usize,
+        derived: &Derived<Package, Range<SemanticVersion>>,
+        external: &External<Package, Range<SemanticVersion>>,
+        current_terms: &Map<Package, Term<Range<SemanticVersion>>>,
+    ) -> String {
+        // TODO: order should be chosen to make it more logical.
+        format!(
+            "Because {} ({}) and {}, {}.",
+            self.format_terms(&derived.terms),
+            ref_id,
+            self.format_external(external),
+            self.format_terms(current_terms)
+        )
+    }
+
+    /// Add an external cause to the chain of explanations.
+    fn and_explain_external(
+        &self,
+        external: &External<Package, Range<SemanticVersion>>,
+        current_terms: &Map<Package, Term<Range<SemanticVersion>>>,
+    ) -> String {
+        format!(
+            "And because {}, {}.",
+            self.format_external(external),
+            self.format_terms(current_terms)
+        )
+    }
+
+    /// Add an already explained incompat to the chain of explanations.
+    fn and_explain_ref(
+        &self,
+        ref_id: usize,
+        derived: &Derived<Package, Range<SemanticVersion>>,
+        current_terms: &Map<Package, Term<Range<SemanticVersion>>>,
+    ) -> String {
+        format!(
+            "And because {} ({}), {}.",
+            self.format_terms(&derived.terms),
+            ref_id,
+            self.format_terms(current_terms)
+        )
+    }
+
+    /// Add an already explained incompat to the chain of explanations.
+    fn and_explain_prior_and_external(
+        &self,
+        prior_external: &External<Package, Range<SemanticVersion>>,
+        external: &External<Package, Range<SemanticVersion>>,
+        current_terms: &Map<Package, Term<Range<SemanticVersion>>>,
+    ) -> String {
+        format!(
+            "And because {} and {}, {}.",
+            self.format_external(prior_external),
+            self.format_external(external),
+            self.format_terms(current_terms)
+        )
+    }
 }
 
 fn main() {

src/internal/core.rs

@@ -16,7 +16,7 @@ use crate::internal::partial_solution::{DecisionLevel, PartialSolution};
 use crate::internal::small_vec::SmallVec;
 use crate::package::Package;
 use crate::report::DerivationTree;
-use crate::type_aliases::{DependencyConstraints, Map, Set};
+use crate::type_aliases::{Map, Set};
 use crate::version_set::VersionSet;
 
 /// Current state of the PubGrub algorithm.
@@ -25,7 +25,8 @@ pub struct State<P: Package, VS: VersionSet, Priority: Ord + Clone> {
     root_package: P,
     root_version: VS::V,
 
-    incompatibilities: Map<P, Vec<IncompId<P, VS>>>,
+    /// The set of incompatibilities for each package.
+    pub incompatibilities: Map<P, Vec<IncompId<P, VS>>>,
 
     /// Store the ids of incompatibilities that are already contradicted.
     /// For each one keep track of the decision level when it was found to be contradicted.
@@ -82,12 +83,12 @@ impl<P: Package, VS: VersionSet, Priority: Ord + Clone> State<P, VS, Priority> {
         &mut self,
         package: P,
         version: VS::V,
-        deps: &DependencyConstraints<P, VS>,
+        deps: impl IntoIterator<Item = (P, VS)>,
     ) -> std::ops::Range<IncompId<P, VS>> {
         // Create incompatibilities and allocate them in the store.
         let new_incompats_id_range =
             self.incompatibility_store
-                .alloc_iter(deps.iter().map(|dep| {
+                .alloc_iter(deps.into_iter().map(|dep| {
                     Incompatibility::from_dependency(
                         package.clone(),
                         VS::singleton(version.clone()),