dag: add EdgesFrom, EdgesTo, needs tests

Author: mitchellh

dag/graph.go

@@ -48,6 +48,32 @@ func (g *Graph) Edges() []Edge {
 	return result
 }
 
+// EdgesFrom returns the list of edges from the given source.
+func (g *Graph) EdgesFrom(v Vertex) []Edge {
+	var result []Edge
+	from := hashcode(v)
+	for _, e := range g.Edges() {
+		if hashcode(e.Source()) == from {
+			result = append(result, e)
+		}
+	}
+
+	return result
+}
+
+// EdgesTo returns the list of edges to the given target.
+func (g *Graph) EdgesTo(v Vertex) []Edge {
+	var result []Edge
+	search := hashcode(v)
+	for _, e := range g.Edges() {
+		if hashcode(e.Target()) == search {
+			result = append(result, e)
+		}
+	}
+
+	return result
+}
+
 // HasVertex checks if the given Vertex is present in the graph.
 func (g *Graph) HasVertex(v Vertex) bool {
 	return g.vertices.Include(v)

terraform/transform_destroy_cbd.go

@@ -50,7 +50,8 @@ func (t *CBDEdgeTransformer) Transform(g *Graph) error {
 		}
 
 		// Find the destroy edge. There should only be one.
-		for _, e := range g.DownEdges(v).List() {
+		for _, e := range g.EdgesTo(v) {
+			log.Printf("WHAT: %#v", e)
 			// Not a destroy edge, ignore it
 			de, ok := e.(*DestroyEdge)
 			if !ok {

terraform/transform_destroy_cbd_test.go

@@ -7,7 +7,8 @@ import (
 
 func TestCBDEdgeTransformer(t *testing.T) {
 	g := Graph{Path: RootModulePath}
-	g.Add(&graphNodeDestroyerTest{AddrString: "test.A"})
+	g.Add(&graphNodeCreatorTest{AddrString: "test.A"})
+	g.Add(&graphNodeDestroyerTest{AddrString: "test.A", CBD: true})
 	g.Add(&graphNodeDestroyerTest{AddrString: "test.B"})
 
 	{
@@ -34,7 +35,9 @@ func TestCBDEdgeTransformer(t *testing.T) {
 }
 
 const testTransformCBDEdgeBasicStr = `
+test.A
 test.A (destroy)
+  test.A
   test.B (destroy)
 test.B (destroy)
 `