1// Copyright 2018, The Go Authors. All rights reserved. 2// Use of this source code is governed by a BSD-style 3// license that can be found in the LICENSE file. 4 5package cmpopts 6 7import ( 8 "github.com/google/go-cmp/cmp" 9) 10 11type xformFilter struct{ xform cmp.Option } 12 13func (xf xformFilter) filter(p cmp.Path) bool { 14 for _, ps := range p { 15 if t, ok := ps.(cmp.Transform); ok && t.Option() == xf.xform { 16 return false 17 } 18 } 19 return true 20} 21 22// AcyclicTransformer returns a Transformer with a filter applied that ensures 23// that the transformer cannot be recursively applied upon its own output. 24// 25// An example use case is a transformer that splits a string by lines: 26// 27// AcyclicTransformer("SplitLines", func(s string) []string{ 28// return strings.Split(s, "\n") 29// }) 30// 31// Had this been an unfiltered Transformer instead, this would result in an 32// infinite cycle converting a string to []string to [][]string and so on. 33func AcyclicTransformer(name string, xformFunc interface{}) cmp.Option { 34 xf := xformFilter{cmp.Transformer(name, xformFunc)} 35 return cmp.FilterPath(xf.filter, xf.xform) 36} 37