| package ast |
| |
| import "fmt" |
| |
| // WalkFunc describes a function to be called for each node during a Walk. The |
| // returned node can be used to rewrite the AST. Walking stops the returned |
| // bool is false. |
| type WalkFunc func(Node) (Node, bool) |
| |
| // Walk traverses an AST in depth-first order: It starts by calling fn(node); |
| // node must not be nil. If fn returns true, Walk invokes fn recursively for |
| // each of the non-nil children of node, followed by a call of fn(nil). The |
| // returned node of fn can be used to rewrite the passed node to fn. |
| func Walk(node Node, fn WalkFunc) Node { |
| rewritten, ok := fn(node) |
| if !ok { |
| return rewritten |
| } |
| |
| switch n := node.(type) { |
| case *File: |
| n.Node = Walk(n.Node, fn) |
| case *ObjectList: |
| for i, item := range n.Items { |
| n.Items[i] = Walk(item, fn).(*ObjectItem) |
| } |
| case *ObjectKey: |
| // nothing to do |
| case *ObjectItem: |
| for i, k := range n.Keys { |
| n.Keys[i] = Walk(k, fn).(*ObjectKey) |
| } |
| |
| if n.Val != nil { |
| n.Val = Walk(n.Val, fn) |
| } |
| case *LiteralType: |
| // nothing to do |
| case *ListType: |
| for i, l := range n.List { |
| n.List[i] = Walk(l, fn) |
| } |
| case *ObjectType: |
| n.List = Walk(n.List, fn).(*ObjectList) |
| default: |
| // should we panic here? |
| fmt.Printf("unknown type: %T\n", n) |
| } |
| |
| fn(nil) |
| return rewritten |
| } |