Reject a folder using the reference prefix, and filter bindings only where they exist

data.go

@@ -55,6 +55,9 @@ func loadDir(dir string) (*group, error) {
 	for _, e := range entries {
 		full := filepath.Join(dir, e.Name())
 		if e.IsDir() {
+			if isRef(e.Name()) {
+				return nil, fmt.Errorf("%s: folder %q starts with %q, which is reserved for {..path} bindings", full, e.Name(), refPrefix)
+			}
 			child, err := loadDir(full)
 			if err != nil {
 				return nil, err

reference.go

@@ -75,7 +75,7 @@ type namedNode struct {
 func contained(n node) []namedNode {
 	switch n := n.(type) {
 	case *group:
-		return named(n.children)
+		return authored(n.children)
 	case *choice:
 		out := make([]namedNode, len(n.items))
 		for i, it := range n.items {
@@ -90,7 +90,8 @@ func contained(n node) []namedNode {
 }
 
 // named skips a bound {..path} key: it is a render edge, not containment, so using
-// it as a path segment would report a node under a path that does not reach it.
+// it as a path segment would report a node under a path that does not reach it. Only
+// a template's fields hold bindings, so group children go through authored.
 func named(m map[string]node) []namedNode {
 	out := make([]namedNode, 0, len(m))
 	for _, name := range sortedNames(m) {
@@ -102,6 +103,14 @@ func named(m map[string]node) []namedNode {
 	return out
 }
 
+func authored(m map[string]node) []namedNode {
+	out := make([]namedNode, 0, len(m))
+	for _, name := range sortedNames(m) {
+		out = append(out, namedNode{name: name, node: m[name]})
+	}
+	return out
+}
+
 func sortedNames(m map[string]node) []string {
 	names := make([]string, 0, len(m))
 	for name := range m {