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// Copyright 2018, The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
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)
}
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