feat(cpp)!: Specify solvable requirements with Requirement

cpp/include/resolvo.h

@@ -4,6 +4,24 @@
 #include "resolvo_internal.h"
 
 namespace resolvo {
+using cbindgen_private::Requirement;
+
+/**
+ * Specifies a requirement (dependency) of a single version set.
+ */
+inline Requirement requirement_single(VersionSetId id) {
+    return cbindgen_private::resolvo_requirement_single(id);
+}
+
+/**
+ * Specifies a requirement (dependency) of the union (logical OR) of multiple version sets.
+ * A solvable belonging to any of the version sets contained in the union satisfies the
+ * requirement. This variant is typically used for requirements that can be satisfied by two
+ * or more version sets belonging to different packages.
+ */
+inline Requirement requirement_union(VersionSetUnionId id) {
+    return cbindgen_private::resolvo_requirement_union(id);
+}
 
 /**
  * Called to solve a package problem.
@@ -12,7 +30,7 @@ namespace resolvo {
  * stored in `result`. If the solve was unsuccesfull an error describing the reason is returned and
  * the result vector will be empty.
  */
-inline String solve(DependencyProvider &provider, Slice<VersionSetId> requirements,
+inline String solve(DependencyProvider &provider, Slice<Requirement> requirements,
                     Slice<VersionSetId> constraints, Vector<SolvableId> &result) {
     cbindgen_private::DependencyProvider bridge{
         static_cast<void *>(&provider),
@@ -24,6 +42,7 @@ inline String solve(DependencyProvider &provider, Slice<VersionSetId> requiremen
         private_api::bridge_display_string,
         private_api::bridge_version_set_name,
         private_api::bridge_solvable_name,
+        private_api::bridge_version_sets_in_union,
         private_api::bridge_get_candidates,
         private_api::bridge_sort_candidates,
         private_api::bridge_filter_candidates,

cpp/include/resolvo_dependency_provider.h

@@ -13,6 +13,7 @@ using cbindgen_private::NameId;
 using cbindgen_private::SolvableId;
 using cbindgen_private::StringId;
 using cbindgen_private::VersionSetId;
+using cbindgen_private::VersionSetUnionId;
 
 /**
  * An interface that implements ecosystem specific logic.
@@ -75,6 +76,11 @@ struct DependencyProvider {
      */
     virtual NameId solvable_name(SolvableId solvable_id) = 0;
 
+    /**
+     * Returns the version sets comprising the given union.
+     */
+    virtual Slice<VersionSetId> version_sets_in_union(VersionSetUnionId version_set_union_id) = 0;
+
     /**
      * Obtains a list of solvables that should be considered when a package
      * with the given name is requested.
@@ -132,6 +138,11 @@ extern "C" inline NameId bridge_version_set_name(void *data, VersionSetId versio
 extern "C" inline NameId bridge_solvable_name(void *data, SolvableId solvable_id) {
     return reinterpret_cast<DependencyProvider *>(data)->solvable_name(solvable_id);
 }
+extern "C" inline Slice<VersionSetId> bridge_version_sets_in_union(
+    void *data, VersionSetUnionId version_set_union_id) {
+    return reinterpret_cast<DependencyProvider *>(data)->version_sets_in_union(
+        version_set_union_id);
+}
 
 extern "C" inline void bridge_get_candidates(void *data, NameId package, Candidates *result) {
     *result = reinterpret_cast<DependencyProvider *>(data)->get_candidates(package);

cpp/src/lib.rs

@@ -31,6 +31,66 @@ impl From<SolvableId> for resolvo::SolvableId {
     }
 }
 
+/// Specifies the dependency of a solvable on a set of version sets.
+/// cbindgen:derive-eq
+/// cbindgen:derive-neq
+#[repr(C)]
+#[derive(Copy, Clone)]
+pub enum Requirement {
+    /// Specifies a dependency on a single version set.
+    /// cbindgen:derive-eq
+    /// cbindgen:derive-neq
+    Single(VersionSetId),
+    /// Specifies a dependency on the union (logical OR) of multiple version sets. A solvable
+    /// belonging to ANY of the version sets contained in the union satisfies the requirement.
+    /// This variant is typically used for requirements that can be satisfied by two or more
+    /// version sets belonging to different packages.
+    /// cbindgen:derive-eq
+    /// cbindgen:derive-neq
+    Union(VersionSetUnionId),
+}
+
+impl From<resolvo::Requirement> for crate::Requirement {
+    fn from(value: resolvo::Requirement) -> Self {
+        match value {
+            resolvo::Requirement::Single(id) => Requirement::Single(id.into()),
+            resolvo::Requirement::Union(id) => Requirement::Union(id.into()),
+        }
+    }
+}
+
+impl From<crate::Requirement> for resolvo::Requirement {
+    fn from(value: crate::Requirement) -> Self {
+        match value {
+            Requirement::Single(id) => resolvo::Requirement::Single(id.into()),
+            Requirement::Union(id) => resolvo::Requirement::Union(id.into()),
+        }
+    }
+}
+
+/// A unique identifier for a version set union. A version set union describes
+/// the union (logical OR) of a non-empty set of version sets belonging to
+/// more than one package.
+/// cbindgen:derive-eq
+/// cbindgen:derive-neq
+#[repr(C)]
+#[derive(Copy, Clone)]
+pub struct VersionSetUnionId {
+    id: u32,
+}
+
+impl From<resolvo::VersionSetUnionId> for crate::VersionSetUnionId {
+    fn from(id: resolvo::VersionSetUnionId) -> Self {
+        Self { id: id.0 }
+    }
+}
+
+impl From<crate::VersionSetUnionId> for resolvo::VersionSetUnionId {
+    fn from(id: crate::VersionSetUnionId) -> Self {
+        Self(id.id)
+    }
+}
+
 /// A unique identifier for a single version set. A version set describes a
 /// set of versions.
 /// cbindgen:derive-eq
@@ -102,7 +162,7 @@ pub struct Dependencies {
     /// A pointer to the first element of a list of requirements. Requirements
     /// defines which packages should be installed alongside the depending
     /// package and the constraints applied to the package.
-    pub requirements: Vector<VersionSetId>,
+    pub requirements: Vector<Requirement>,
 
     /// Defines additional constraints on packages that may or may not be part
     /// of the solution. Different from `requirements`, packages in this set
@@ -230,6 +290,12 @@ pub struct DependencyProvider {
     /// Returns the name of the package for the given solvable.
     pub solvable_name: unsafe extern "C" fn(data: *mut c_void, solvable_id: SolvableId) -> NameId,
 
+    /// Returns the version sets comprising the given union.
+    pub version_sets_in_union: unsafe extern "C" fn(
+        data: *mut c_void,
+        version_set_union_id: VersionSetUnionId,
+    ) -> Slice<'static, VersionSetId>,
+
     /// Obtains a list of solvables that should be considered when a package
     /// with the given name is requested.
     pub get_candidates:
@@ -314,6 +380,17 @@ impl<'d> resolvo::Interner for &'d DependencyProvider {
     fn solvable_name(&self, solvable: resolvo::SolvableId) -> resolvo::NameId {
         unsafe { (self.solvable_name)(self.data, solvable.into()) }.into()
     }
+
+    fn version_sets_in_union(
+        &self,
+        version_set_union: resolvo::VersionSetUnionId,
+    ) -> impl Iterator<Item = resolvo::VersionSetId> {
+        unsafe { (self.version_sets_in_union)(self.data, version_set_union.into()) }
+            .as_slice()
+            .into_iter()
+            .copied()
+            .map(Into::into)
+    }
 }
 
 impl<'d> resolvo::DependencyProvider for &'d DependencyProvider {
@@ -400,7 +477,7 @@ impl<'d> resolvo::DependencyProvider for &'d DependencyProvider {
 #[allow(unused)]
 pub extern "C" fn resolvo_solve(
     provider: &DependencyProvider,
-    requirements: Slice<VersionSetId>,
+    requirements: Slice<Requirement>,
     constraints: Slice<VersionSetId>,
     error: &mut String,
     result: &mut Vector<SolvableId>,
@@ -433,6 +510,20 @@ pub extern "C" fn resolvo_solve(
     }
 }
 
+#[no_mangle]
+#[allow(unused)]
+pub extern "C" fn resolvo_requirement_single(version_set_id: VersionSetId) -> Requirement {
+    Requirement::Single(version_set_id)
+}
+
+#[no_mangle]
+#[allow(unused)]
+pub extern "C" fn resolvo_requirement_union(
+    version_set_union_id: VersionSetUnionId,
+) -> Requirement {
+    Requirement::Union(version_set_union_id)
+}
+
 #[cfg(test)]
 mod tests {
     use super::*;

cpp/tests/solve.cpp

@@ -16,9 +16,9 @@ struct Candidate {
 };
 
 /**
- * A requirement for a package.
+ * A version set for a package.
  */
-struct Requirement {
+struct VersionSet {
     resolvo::NameId name;
     uint32_t version_start;
     uint32_t version_end;
@@ -31,19 +31,47 @@ struct PackageDatabase : public resolvo::DependencyProvider {
     resolvo::Pool<resolvo::NameId, resolvo::String> names;
     resolvo::Pool<resolvo::StringId, resolvo::String> strings;
     std::vector<Candidate> candidates;
-    std::vector<Requirement> requirements;
+    std::vector<VersionSet> version_sets;
+    std::vector<std::vector<resolvo::VersionSetId>> version_set_unions;
 
     /**
-     * Allocates a new requirement and return the id of the requirement.
+     * Allocates a new version set and return the id of the version set.
      */
-    resolvo::VersionSetId alloc_requirement(std::string_view package, uint32_t version_start,
+    resolvo::VersionSetId alloc_version_set(std::string_view package, uint32_t version_start,
                                             uint32_t version_end) {
         auto name_id = names.alloc(std::move(package));
-        auto id = resolvo::VersionSetId{static_cast<uint32_t>(requirements.size())};
-        requirements.push_back(Requirement{name_id, version_start, version_end});
+        auto id = resolvo::VersionSetId{static_cast<uint32_t>(version_sets.size())};
+        version_sets.push_back(VersionSet{name_id, version_start, version_end});
         return id;
     }
 
+    /**
+     * Allocates a new requirement for a single version set.
+     */
+    resolvo::Requirement alloc_requirement(std::string_view package, uint32_t version_start,
+                                           uint32_t version_end) {
+        auto id = alloc_version_set(package, version_start, version_end);
+        return resolvo::requirement_single(id);
+    }
+
+    /**
+     * Allocates a new requirement for a version set union.
+     */
+    resolvo::Requirement alloc_requirement_union(
+        std::initializer_list<std::tuple<std::string_view, uint32_t, uint32_t>> version_sets) {
+        std::vector<resolvo::VersionSetId> version_set_union{version_sets.size()};
+
+        auto version_sets_it = version_sets.begin();
+        for (size_t i = 0; i < version_sets.size(); ++i, ++version_sets_it) {
+            auto [package, version_start, version_end] = *version_sets_it;
+            version_set_union[i] = alloc_version_set(package, version_start, version_end);
+        }
+
+        auto id = resolvo::VersionSetUnionId{static_cast<uint32_t>(version_set_unions.size())};
+        version_set_unions.push_back(std::move(version_set_union));
+        return resolvo::requirement_union(id);
+    }
+
     /**
      * Allocates a new candidate and return the id of the candidate.
      */
@@ -90,7 +118,7 @@ struct PackageDatabase : public resolvo::DependencyProvider {
     }
 
     resolvo::String display_version_set(resolvo::VersionSetId version_set) override {
-        const auto& req = requirements[version_set.id];
+        const auto& req = version_sets[version_set.id];
         std::stringstream ss;
         ss << req.version_start << ".." << req.version_end;
         return resolvo::String(ss.str());
@@ -101,13 +129,19 @@ struct PackageDatabase : public resolvo::DependencyProvider {
     }
 
     resolvo::NameId version_set_name(resolvo::VersionSetId version_set_id) override {
-        return requirements[version_set_id.id].name;
+        return version_sets[version_set_id.id].name;
     }
 
     resolvo::NameId solvable_name(resolvo::SolvableId solvable_id) override {
         return candidates[solvable_id.id].name;
     }
 
+    resolvo::Slice<resolvo::VersionSetId> version_sets_in_union(
+        resolvo::VersionSetUnionId version_set_union_id) override {
+        const auto& version_set_ids = version_set_unions[version_set_union_id.id];
+        return {version_set_ids.data(), version_set_ids.size()};
+    }
+
     resolvo::Candidates get_candidates(resolvo::NameId package) override {
         resolvo::Candidates result;
 
@@ -137,11 +171,11 @@ struct PackageDatabase : public resolvo::DependencyProvider {
         resolvo::Slice<resolvo::SolvableId> solvables, resolvo::VersionSetId version_set_id,
         bool inverse) override {
         resolvo::Vector<resolvo::SolvableId> result;
-        const auto& requirement = requirements[version_set_id.id];
+        const auto& version_set = version_sets[version_set_id.id];
         for (auto solvable : solvables) {
             const auto& candidate = candidates[solvable.id];
-            bool matches = candidate.version >= requirement.version_start &&
-                           candidate.version < requirement.version_end;
+            bool matches = candidate.version >= version_set.version_start &&
+                           candidate.version < version_set.version_end;
             if (matches != inverse) {
                 result.push_back(solvable);
             }
@@ -183,9 +217,9 @@ SCENARIO("Solve") {
     auto c_1 = db.alloc_candidate("c", 1, {});
 
     // Construct a problem to be solved by the solver
-    resolvo::Vector<resolvo::VersionSetId> requirements = {db.alloc_requirement("a", 1, 3)};
-    resolvo::Vector<resolvo::VersionSetId> constraints = {db.alloc_requirement("b", 1, 3),
-                                                          db.alloc_requirement("c", 1, 3)};
+    resolvo::Vector<resolvo::Requirement> requirements = {db.alloc_requirement("a", 1, 3)};
+    resolvo::Vector<resolvo::VersionSetId> constraints = {db.alloc_version_set("b", 1, 3),
+                                                          db.alloc_version_set("c", 1, 3)};
 
     // Solve the problem
     resolvo::Vector<resolvo::SolvableId> result;
@@ -196,3 +230,46 @@ SCENARIO("Solve") {
     REQUIRE(result[0] == a_2);
     REQUIRE(result[1] == b_2);
 }
+
+SCENARIO("Solve Union") {
+    /// Construct a database with packages a, b, and c.
+    PackageDatabase db;
+
+    // Check that PackageDatabase correctly implements the DependencyProvider interface
+    static_assert(std::has_virtual_destructor_v<PackageDatabase>);
+    static_assert(std::is_polymorphic_v<PackageDatabase>);
+    static_assert(std::is_base_of_v<resolvo::DependencyProvider, PackageDatabase>);
+
+    auto a_1 = db.alloc_candidate("a", 1, {});
+
+    auto b_1 = db.alloc_candidate("b", 1, {});
+
+    auto c_1 = db.alloc_candidate("c", 1, {{db.alloc_requirement("a", 1, 10)}, {}});
+
+    auto d_1 = db.alloc_candidate("d", 1, {{db.alloc_requirement("b", 1, 10)}, {}});
+
+    auto e_1 = db.alloc_candidate("e", 1,
+                                  {{db.alloc_requirement_union({{"a", 1, 10}, {"b", 1, 10}})}, {}});
+
+    auto f_1 = db.alloc_candidate(
+        "f", 1, {{db.alloc_requirement("b", 1, 10)}, {db.alloc_version_set("a", 10, 20)}});
+
+    // Construct a problem to be solved by the solver
+    resolvo::Vector<resolvo::Requirement> requirements = {
+        db.alloc_requirement_union({{"c", 1, 10}, {"d", 1, 10}}),
+        db.alloc_requirement("e", 1, 10),
+        db.alloc_requirement("f", 1, 10),
+    };
+    resolvo::Vector<resolvo::VersionSetId> constraints = {};
+
+    // Solve the problem
+    resolvo::Vector<resolvo::SolvableId> result;
+    resolvo::solve(db, requirements, constraints, result);
+
+    // Check the result
+    REQUIRE(result.size() == 4);
+    REQUIRE(result[0] == f_1);
+    REQUIRE(result[1] == e_1);
+    REQUIRE(result[2] == b_1);
+    REQUIRE(result[3] == d_1);
+}