diff --git a/build/rule.go b/build/rule.go
index 44bb161ea..650d95aef 100644
--- a/build/rule.go
+++ b/build/rule.go
@@ -226,6 +226,19 @@ func (r *Rule) AttrKeys() []string {
 	return keys
 }
 
+// AttrMap returns the map of attribute keys to values.
+func (r *Rule) AttrMap() map[string]Expr {
+	m := make(map[string]Expr)
+	for _, expr := range r.Call.List {
+		if as, ok := expr.(*AssignExpr); ok {
+			if keyExpr, ok := as.LHS.(*Ident); ok {
+				m[keyExpr.Name] = as.RHS
+			}
+		}
+	}
+	return m
+}
+
 // AttrDefn returns the AssignExpr defining the rule's attribute with the given key.
 // If the rule has no such attribute, AttrDefn returns nil.
 func (r *Rule) AttrDefn(key string) *AssignExpr {