From 1e9020de4c2c120f0ccdba325a616a9b10aceee5 Mon Sep 17 00:00:00 2001
From: Cristian Maglie <c.maglie@bug.st>
Date: Fri, 7 Apr 2023 14:52:01 +0200
Subject: [PATCH] Speedup dependency resolver by pre-cutting unsolvable
 branches

---
 resolver.go      | 22 +++++++++++++++++++---
 resolver_test.go |  3 ++-
 2 files changed, 21 insertions(+), 4 deletions(-)

diff --git a/resolver.go b/resolver.go
index 9f48357..ca469fa 100644
--- a/resolver.go
+++ b/resolver.go
@@ -74,7 +74,7 @@ func (ar *Archive) resolve(solution map[string]Release, depsToProcess []Dependen
 	// Pick the first dependency in the deps to process
 	dep := depsToProcess[0]
 	depName := dep.GetName()
-	debug("Considering next dep: %s", dep)
+	debug("Considering next dep: %s", depName)
 
 	// If a release is already picked in the solution check if it match the dep
 	if existingRelease, has := solution[depName]; has {
@@ -92,11 +92,27 @@ func (ar *Archive) resolve(solution map[string]Release, depsToProcess []Dependen
 	// Consider the latest versions first
 	releases.SortDescent()
 
+	findMissingDeps := func(deps []Dependency) Dependency {
+		for _, dep := range deps {
+			if _, ok := ar.Releases[dep.GetName()]; !ok {
+				return dep
+			}
+		}
+		return nil
+	}
+
 	debug("releases matching criteria: %s", releases)
 	for _, release := range releases {
-		debug("try with %s %s", release, release.GetDependencies())
+		deps := release.GetDependencies()
+		debug("try with %s %s", release, deps)
+
+		if missingDep := findMissingDeps(deps); missingDep != nil {
+			debug("%s did not work, becuase his dependency %s does not exists", release, missingDep.GetName())
+			continue
+		}
+
 		solution[depName] = release
-		res := ar.resolve(solution, append(depsToProcess[1:], release.GetDependencies()...))
+		res := ar.resolve(solution, append(depsToProcess[1:], deps...))
 		if res != nil {
 			return res
 		}
diff --git a/resolver_test.go b/resolver_test.go
index 0435427..55b6a5c 100644
--- a/resolver_test.go
+++ b/resolver_test.go
@@ -94,12 +94,13 @@ func TestResolver(t *testing.T) {
 	d100 := rel("D", "1.0.0", deps())
 	d120 := rel("D", "1.2.0", deps("E"))
 	e100 := rel("E", "1.0.0", deps())
+	e101 := rel("E", "1.0.1", deps("F")) // INVALID
 	arch := &Archive{
 		Releases: map[string]Releases{
 			"B": {b131, b130, b121, b120, b111, b110, b100},
 			"C": {c200, c120, c111, c110, c102, c101, c100, c021, c020, c010},
 			"D": {d100, d120},
-			"E": {e100},
+			"E": {e100, e101},
 		},
 	}