fix: always include start node in neighbours search

Previously was returning an empty graph if there were no neighbours.

pkg/graph/helpers_test.go

@@ -18,6 +18,14 @@ type rule = korrel8r.Rule
 
 func c(i int) korrel8r.Class { return Domain.Class(strconv.Itoa(i)) }
 
+func nodesToInts(nodes []*Node) (ret []int) {
+	for _, n := range nodes {
+		i,_ := strconv.Atoi(n.Class.Name())
+		ret = append(ret, i)
+	}
+	return ret
+}
+
 func testGraph(rules []korrel8r.Rule) *Graph {
 	d := NewData()
 	for _, r := range rules {

pkg/graph/traverse.go

@@ -32,6 +32,7 @@ func (g *Graph) Traverse(start korrel8r.Class, goals []korrel8r.Class, f func(*L
 // Returns the subset of the graph that was traversed.
 func (g *Graph) Neighbours(start korrel8r.Class, depth int, f func(*Line) bool) (*Graph, error) {
 	sub := g.Data.EmptyGraph()
+	sub.AddNode(g.NodeFor(start))
 	atDepth := 0
 	current := unique.Set[int64]{} // Nodes at the current depth or above.
 

pkg/graph/traverse_test.go

@@ -7,22 +7,13 @@ import (
 	"testing"
 
 	"github.com/korrel8r/korrel8r/pkg/korrel8r"
-	"github.com/korrel8r/korrel8r/pkg/unique"
 	"github.com/stretchr/testify/assert"
 )
 
-type collecter struct {
-	rules   []string
-	classes unique.Set[string]
-}
+type ruleCollecter struct {	rules []string }
 
-func (c *collecter) Traverse(l *Line) bool {
+func (c *ruleCollecter) Traverse(l *Line) bool {
 	c.rules = append(c.rules, RuleFor(l).Name())
-	if c.classes == nil {
-		c.classes = unique.NewSet[string]()
-	}
-	c.classes.Add(ClassFor(l.From()).String())
-	c.classes.Add(ClassFor(l.To()).String())
 	return true
 }
 
@@ -34,31 +25,34 @@ func TestTraverse(t *testing.T) {
 		name    string
 		graph   []rule
 		rules   [][]string // inner slices are are unordered components.
-		classes unique.Set[string]
+		nodes   []int
 	}{
 		{
 			name:    "multipath",
 			graph:   []rule{r(1, 11), r(1, 12), r(11, 99), r(12, 99)},
 			rules:   [][]string{{"1_11", "1_12"}, {"11_99", "12_99"}},
-			classes: unique.NewSet("1", "11", "12", "99"),
+			nodes: []int{1, 11, 12, 99},
 		},
 		{
 			name:  "simple",
 			graph: []rule{r(1, 2), r(2, 3), r(3, 4), r(4, 5)},
 			rules: [][]string{{"1_2"}, {"2_3"}, {"3_4"}, {"4_5"}},
+			nodes: []int{1,2,3,4,5},
 		},
 		{
 			name:  "cycle", // cycle of 2,3,4
 			graph: []rule{r(1, 2), r(2, 3), r(3, 4), r(4, 2), r(4, 5)},
 			rules: [][]string{{"1_2"}, {"2_3", "3_4", "4_2", "4_5"}},
+			nodes: []int{1,2,3,4,5},
 		},
 	} {
 		t.Run(x.name, func(t *testing.T) {
 			g := testGraph(x.graph)
-			var got collecter
+			var got ruleCollecter
 			_, err := g.Traverse(x.graph[0].Start()[0], x.graph[len(x.graph)-1].Goal(), got.Traverse)
 			assert.NoError(t, err)
 			assertComponentOrder(t, x.rules, got.rules)
+			assert.ElementsMatch(t, x.nodes, nodesToInts(g.AllNodes()))
 		})
 	}
 }
@@ -70,26 +64,37 @@ func TestNeighbours(t *testing.T) {
 	g := testGraph([]rule{r(1, 11), r(11, 1), r(1, 12), r(1, 13), r(11, 22), r(12, 22), r(12, 13), r(22, 99)})
 	for _, x := range []struct {
 		depth int
-		want  [][]string
+		rules  [][]string
+		nodes []int
 	}{
+		{
+			depth: 0,
+			rules:  nil,
+			nodes: []int{1},
+		},
 		{
 			depth: 1,
-			want:  [][]string{{"1_11", "1_12", "1_13"}},
+			rules:  [][]string{{"1_11", "1_12", "1_13"}},
+			nodes: []int{1,11,12,13},
 		},
 		{
 			depth: 2,
-			want:  [][]string{{"1_11", "1_12", "1_13"}, {"11_22", "12_22"}},
+			rules:  [][]string{{"1_11", "1_12", "1_13"}, {"11_22", "12_22"}},
+			nodes: []int{1,11,12,13,22},
 		},
 		{
 			depth: 3,
-			want:  [][]string{{"1_11", "1_12", "1_13"}, {"11_22", "12_22"}, {"22_99"}},
+			rules:  [][]string{{"1_11", "1_12", "1_13"}, {"11_22", "12_22"}, {"22_99"}},
+			nodes: []int{1,11,12,13,22,99},
 		},
 	} {
 		t.Run(fmt.Sprintf("depth=%v", x.depth), func(t *testing.T) {
-			var got collecter
-			_, err := g.Neighbours(c(1), x.depth, got.Traverse)
+			var got ruleCollecter
+			g2, err := g.Neighbours(c(1), x.depth, got.Traverse)
 			assert.NoError(t, err)
-			assertComponentOrder(t, x.want, got.rules)
+			assertComponentOrder(t, x.rules, got.rules)
+			assert.ElementsMatch(t, x.nodes, nodesToInts(g2.AllNodes()))
 		})
 	}
 }
+