Consider the greatest version matching the constraints first

Author: cmaglie

resolver.go

@@ -6,6 +6,8 @@
 
 package semver
 
+import "sort"
+
 // Dependency represents a dependency, it must provide methods to return Name and Constraints
 type Dependency interface {
 	GetName() string
@@ -37,6 +39,14 @@ func (set Releases) FilterBy(dep Dependency) Releases {
 	return res
 }
 
+// SortDescent sort the Releases in this set in descending order (the lastest
+// release is the first)
+func (set Releases) SortDescent() {
+	sort.Slice(set, func(i, j int) bool {
+		return set[i].GetVersion().GreaterThan(set[j].GetVersion())
+	})
+}
+
 // Archive contains all Releases set to consider for dependency resolution
 type Archive struct {
 	Releases map[string]Releases
@@ -78,6 +88,10 @@ func (ar *Archive) resolve(solution map[string]Release, depsToProcess []Dependen
 
 	// Otherwise start backtracking the dependency
 	releases := ar.Releases[dep.GetName()].FilterBy(dep)
+
+	// Consider the latest versions first
+	releases.SortDescent()
+
 	debug("releases matching criteria: %s", releases)
 	for _, release := range releases {
 		debug("try with %s %s", release, release.GetDependencies())

resolver_test.go

@@ -90,11 +90,16 @@ func TestResolver(t *testing.T) {
 	c100 := rel("C", "1.0.0", deps())
 	c021 := rel("C", "0.2.1", deps())
 	c020 := rel("C", "0.2.0", deps())
-	c010 := rel("C", "0.1.0", deps())
+	c010 := rel("C", "0.1.0", deps("D"))
+	d100 := rel("D", "1.0.0", deps())
+	d120 := rel("D", "1.2.0", deps("E"))
+	e100 := rel("E", "1.0.0", deps())
 	arch := &Archive{
 		Releases: map[string]Releases{
 			"B": Releases{b131, b130, b121, b120, b111, b110, b100},
 			"C": Releases{c200, c120, c111, c110, c102, c101, c100, c021, c020, c010},
+			"D": Releases{d100, d120},
+			"E": Releases{e100},
 		},
 	}
 
@@ -127,4 +132,10 @@ func TestResolver(t *testing.T) {
 	r4 := arch.Resolve(a120)
 	require.Nil(t, r4)
 	fmt.Println(r4)
+
+	r5 := arch.Resolve(c010)
+	require.Contains(t, r5, c010)
+	require.Contains(t, r5, d120)
+	require.Contains(t, r5, e100)
+	fmt.Println(r5)
 }