1package ast 2 3import "fmt" 4 5// WalkFunc describes a function to be called for each node during a Walk. The 6// returned node can be used to rewrite the AST. Walking stops the returned 7// bool is false. 8type WalkFunc func(Node) (Node, bool) 9 10// Walk traverses an AST in depth-first order: It starts by calling fn(node); 11// node must not be nil. If fn returns true, Walk invokes fn recursively for 12// each of the non-nil children of node, followed by a call of fn(nil). The 13// returned node of fn can be used to rewrite the passed node to fn. 14func Walk(node Node, fn WalkFunc) Node { 15 rewritten, ok := fn(node) 16 if !ok { 17 return rewritten 18 } 19 20 switch n := node.(type) { 21 case *File: 22 n.Node = Walk(n.Node, fn) 23 case *ObjectList: 24 for i, item := range n.Items { 25 n.Items[i] = Walk(item, fn).(*ObjectItem) 26 } 27 case *ObjectKey: 28 // nothing to do 29 case *ObjectItem: 30 for i, k := range n.Keys { 31 n.Keys[i] = Walk(k, fn).(*ObjectKey) 32 } 33 34 if n.Val != nil { 35 n.Val = Walk(n.Val, fn) 36 } 37 case *LiteralType: 38 // nothing to do 39 case *ListType: 40 for i, l := range n.List { 41 n.List[i] = Walk(l, fn) 42 } 43 case *ObjectType: 44 n.List = Walk(n.List, fn).(*ObjectList) 45 default: 46 // should we panic here? 47 fmt.Printf("unknown type: %T\n", n) 48 } 49 50 fn(nil) 51 return rewritten 52} 53