add Siblings() with tests

traversal.go

@@ -178,6 +178,12 @@ func (this *Selection) ParentsFilteredUntilNodes(filterSelector string, nodes ..
 	return pushStack(this, n)
 }
 
+// Siblings() gets the siblings of each element in the Selection. It returns
+// a new Selection object containing the matched elements.
+func (this *Selection) Siblings() *Selection {
+	return pushStack(this, getSiblingNodes(this.Nodes))
+}
+
 // Internal implementation to get all parent nodes, stopping at the specified 
 // node (or nil if no stop).
 func getParentsNodes(nodes []*html.Node, stopSelector string, stopNodes []*html.Node) []*html.Node {
@@ -201,6 +207,20 @@ func getParentsNodes(nodes []*html.Node, stopSelector string, stopNodes []*html.
 	})
 }
 
+// Internal implementation of sibling nodes that return a raw slice of matches.
+func getSiblingNodes(nodes []*html.Node) []*html.Node {
+	return mapNodes(nodes, func(i int, n *html.Node) (result []*html.Node) {
+		if p := n.Parent; p != nil {
+			for _, c := range p.Child {
+				if c != n && c.Type == html.ElementNode {
+					result = append(result, c)
+				}
+			}
+		}
+		return
+	})
+}
+
 // Internal implementation of parent nodes that return a raw slice of Nodes.
 func getParentNodes(nodes []*html.Node) []*html.Node {
 	return mapNodes(nodes, func(i int, n *html.Node) []*html.Node {
@@ -247,6 +267,7 @@ func findWithContext(selector string, nodes ...*html.Node) []*html.Node {
 // Return the child nodes of each node in the Selection object, without
 // duplicates.
 func getSelectionChildren(s *Selection, elemOnly bool) (result []*html.Node) {
+	// TODO : Refactor to use mapNodes?
 	for _, n := range s.Nodes {
 		result = appendWithoutDuplicates(result, getChildren(n, elemOnly))
 	}

traversal_test.go

@@ -112,3 +112,13 @@ func TestParentsFilteredUntilNodes(t *testing.T) {
 	sel = sel.ParentsFilteredUntilNodes("body", sel2.Nodes...)
 	AssertLength(t, sel.Nodes, 1)
 }
+
+func TestSiblings(t *testing.T) {
+	sel := Doc().Root.Find("h1").Siblings()
+	AssertLength(t, sel.Nodes, 1)
+}
+
+func TestSiblings2(t *testing.T) {
+	sel := Doc().Root.Find(".pvk-gutter").Siblings()
+	AssertLength(t, sel.Nodes, 9)
+}