Support version relation in Provides entries

deb/list.go

@@ -145,7 +145,7 @@ func (l *PackageList) Add(p *Package) error {
 	l.packages[key] = p
 
 	if l.indexed {
-		for _, provides := range p.Provides {
+		for _, provides := range p.ProvidedPackages() {
 			l.providesIndex[provides] = append(l.providesIndex[provides], p)
 		}
 
@@ -215,7 +215,7 @@ func (l *PackageList) Append(pl *PackageList) error {
 func (l *PackageList) Remove(p *Package) {
 	delete(l.packages, l.keyFunc(p))
 	if l.indexed {
-		for _, provides := range p.Provides {
+		for _, provides := range p.ProvidedPackages() {
 			for i, pkg := range l.providesIndex[provides] {
 				if pkg.Equals(p) {
 					// remove l.ProvidesIndex[provides][i] w/o preserving order
@@ -419,7 +419,7 @@ func (l *PackageList) PrepareIndex() {
 		l.packagesIndex[i] = p
 		i++
 
-		for _, provides := range p.Provides {
+		for _, provides := range p.ProvidedPackages() {
 			l.providesIndex[provides] = append(l.providesIndex[provides], p)
 		}
 	}
@@ -472,21 +472,25 @@ func (l *PackageList) Search(dep Dependency, allMatches bool) (searchResults []*
 			searchResults = append(searchResults, p)
 
 			if !allMatches {
-				break
+				return
 			}
 		}
 
 		i++
 	}
 
-	if dep.Relation == VersionDontCare {
-		for _, p := range l.providesIndex[dep.Pkg] {
-			if dep.Architecture == "" || p.MatchesArchitecture(dep.Architecture) {
+	providers, ok := l.providesIndex[dep.Pkg]
+	if !ok {
+		return
+	}
+	for _, p := range providers {
+		if dep.Architecture == "" || p.MatchesArchitecture(dep.Architecture) {
+			if p.MatchesDependency(dep) {
 				searchResults = append(searchResults, p)
+			}
 
-				if !allMatches {
-					break
-				}
+			if !allMatches {
+				return
 			}
 		}
 	}

deb/package.go

@@ -3,6 +3,7 @@ package deb
 import (
 	gocontext "context"
 	"encoding/json"
+	"errors"
 	"fmt"
 	"path/filepath"
 	"strconv"
@@ -312,6 +313,23 @@ func (p *Package) GetField(name string) string {
 	}
 }
 
+// ProvidedPackages returns just the package names of the provided packages (without version numbers such as
+// `(= 1.2.3)`).
+func (p *Package) ProvidedPackages() []string {
+	result := make([]string, len(p.Provides))
+	for i, provided := range p.Provides {
+		providedDep, err := ParseDependency(provided)
+		if err != nil {
+			// Should never happen, but I included this, so it definitely has the old behavior in case there is no
+			// special syntax.
+			result[i] = provided
+		} else {
+			result[i] = providedDep.Pkg
+		}
+	}
+	return result
+}
+
 // MatchesArchitecture checks whether packages matches specified architecture
 func (p *Package) MatchesArchitecture(arch string) bool {
 	if p.Architecture == ArchitectureAll && arch != ArchitectureSource {
@@ -321,24 +339,57 @@ func (p *Package) MatchesArchitecture(arch string) bool {
 	return p.Architecture == arch
 }
 
+// providesDependency checks if the package `Provide:`s the dependency, assuming that the architecture matches.
+// If the `Provides:` entry includes a version number, it will be considered when checking the dependency.
+func (p *Package) providesDependency(dep Dependency) (bool, error) {
+	var errs []error // won't cause an allocation in case of no errors
+	for _, provided := range p.Provides {
+		providedDep, err := ParseDependency(provided)
+		if err != nil {
+			errs = append(errs, err)
+		}
+		// The only relation allowed here is `=`.
+		// > The relations allowed are [...]. The exception is the Provides field, for which only = is allowed.
+		// > [...]
+		// > A Provides field may contain version numbers, and such a version number will be considered when
+		// > considering a dependency on or conflict with the virtual package name.
+		// -- https://www.debian.org/doc/debian-policy/ch-relationships.html
+		switch providedDep.Relation {
+		case VersionDontCare:
+			if providedDep.Pkg == dep.Pkg {
+				return true, nil
+			}
+		case VersionEqual:
+			providedVersion := providedDep.Version
+			if providedDep.Pkg == dep.Pkg && versionSatisfiesDependency(providedVersion, dep) {
+				return true, nil
+			}
+		default:
+			errs = append(errs, fmt.Errorf("unsupported relation in Provides: %s", providedDep.String()))
+		}
+	}
+	return false, errors.Join(errs...)
+}
+
 // MatchesDependency checks whether package matches specified dependency
 func (p *Package) MatchesDependency(dep Dependency) bool {
 	if dep.Architecture != "" && !p.MatchesArchitecture(dep.Architecture) {
 		return false
 	}
 
-	if dep.Relation == VersionDontCare {
-		if utils.StrSliceHasItem(p.Provides, dep.Pkg) {
-			return true
-		}
-		return dep.Pkg == p.Name
+	if providesDep, _ := p.providesDependency(dep); providesDep { // Is ignoring errors the right thing to do here?
+		return true
 	}
 
 	if dep.Pkg != p.Name {
 		return false
 	}
 
-	r := CompareVersions(p.Version, dep.Version)
+	return versionSatisfiesDependency(p.Version, dep)
+}
+
+func versionSatisfiesDependency(version string, dep Dependency) bool {
+	r := CompareVersions(version, dep.Version)
 
 	switch dep.Relation {
 	case VersionEqual:
@@ -352,13 +403,15 @@ func (p *Package) MatchesDependency(dep Dependency) bool {
 	case VersionGreaterOrEqual:
 		return r >= 0
 	case VersionPatternMatch:
-		matched, err := filepath.Match(dep.Version, p.Version)
+		matched, err := filepath.Match(dep.Version, version)
 		return err == nil && matched
 	case VersionRegexp:
-		return dep.Regexp.FindStringIndex(p.Version) != nil
+		return dep.Regexp.FindStringIndex(version) != nil
+	case VersionDontCare:
+		return true
+	default:
+		panic(fmt.Sprintf("unknown relation: %d", dep.Relation))
 	}
-
-	panic("unknown relation")
 }
 
 // GetName returns package name