Source: xform.go in package github.com/google/go-cmp/cmp/cmpopts


package cmpopts

import (
	"github.com/google/go-cmp/cmp"
)

type xformFilter struct{ xform cmp.Option }

func (xf xformFilter) filter(p cmp.Path) bool {
	for _, ps := range p {
		if t, ok := ps.(cmp.Transform); ok && t.Option() == xf.xform {
			return false
		}
	}
	return true
}

AcyclicTransformer returns a Transformer with a filter applied that ensures that the transformer cannot be recursively applied upon its own output. An example use case is a transformer that splits a string by lines: AcyclicTransformer("SplitLines", func(s string) []string{ return strings.Split(s, "\n") }) Had this been an unfiltered Transformer instead, this would result in an infinite cycle converting a string to []string to [][]string and so on.

func AcyclicTransformer(name string, xformFunc interface{}) cmp.Option {
	xf := xformFilter{cmp.Transformer(name, xformFunc)}
	return cmp.FilterPath(xf.filter, xf.xform)