Merge pull request #73 from hmdsefi/dev

fix finding cycle in directed graph

Author: hmdsefi

base.go

@@ -69,6 +69,9 @@ func (g *baseGraph[T]) AddEdge(from, to *Vertex[T], options ...EdgeOptionFunc) (
 		return nil, ErrEdgeAlreadyExists
 	}
 
+	from = g.vertices[from.label]
+	to = g.vertices[to.label]
+
 	from.neighbors = append(from.neighbors, to)
 	to.inDegree++
 

base_test.go

@@ -1,6 +1,7 @@
 package gograph
 
 import (
+	"errors"
 	"reflect"
 	"testing"
 )
@@ -890,3 +891,24 @@ func Test_baseGraph_ContainsVertex(t *testing.T) {
 		t.Errorf("expected len to be %d, but receive %d", 3, len(edges))
 	}
 }
+
+func Test_baseGraph_Cyclic(t *testing.T) {
+	graph := New[int](Acyclic())
+
+	_, err := graph.AddEdge(NewVertex(1), NewVertex(2))
+	if err != nil {
+		t.Fatal(err)
+	}
+	_, err = graph.AddEdge(NewVertex(2), NewVertex(3))
+	if err != nil {
+		t.Fatal(err)
+	}
+	_, err = graph.AddEdge(NewVertex(3), NewVertex(1))
+	if err == nil {
+		t.Fatalf("expected error, but got nil")
+	}
+
+	if !errors.Is(err, ErrDAGCycle) {
+		t.Errorf("expected error %s, but got %s", ErrDAGCycle, err)
+	}
+}