ensure that self-edges are correctly filtered in reachability analysis

pkg/graph/graph.go

@@ -196,7 +196,8 @@ func (g *Graph) ReachableFrom(roots []*model.NameReference, maxDepth int) *Graph
 		for _, edge := range edges {
 			_, srcPresent := filteredNodes[edge.src.Name]
 			_, dstPresent := filteredNodes[edge.dst.Name]
-			if srcPresent && dstPresent {
+			fieldPresent := edge.field == nil || seen.includesField(edge.src.Name, edge.field.Name)
+			if srcPresent && dstPresent && fieldPresent {
 				filtered = append(filtered, edge)
 			}
 		}

pkg/graph/graph_test.go

@@ -207,6 +207,29 @@ func TestReachableFrom(t *testing.T) {
 				},
 			},
 		},
+		{
+			name: "filtered self edges",
+			schema: `type Person {
+				hobbies: [Hobby]
+				friends: [Person]
+			}
+
+			type Hobby {
+				name: String
+			}
+			`,
+			roots:          []string{"Person.hobbies"},
+			maxDepth:       2,
+			expectedNodes:  []string{"Hobby", "Person"},
+			expectedFields: []string{"Hobby.name", "Person.hobbies"},
+			expectedEdges: []edgeSpec{
+				{
+					srcType:   "Person",
+					dstType:   "Hobby",
+					fieldName: "hobbies",
+				},
+			},
+		},
 	} {
 		t.Run(tc.name, func(t *testing.T) {
 			src := ast.Source{