strings: Replacer doesn't seem to replace correctly

[sjpotter]

using go 1.5.1 and 1.6 on linux/x64

given this string

var cgroupname = "/machine.slice/machine-rkt\\x2dbad20ebf\\x2de8b8\\x2d48fe\\x2dabba\\x2de2e3f72123fb.scope/system.slice/alpine-sh.service"

trying to use this function to strip out part of it. (yes, can use regex, but that's a different point)

func parseName(name string) (string, error) {
        splits := strings.Split(name, "/")
        if len(splits) == 3 || len(splits) == 5 {
                if splits[1] == "machine.slice" {
                        replacer := strings.NewReplacer("machine-rkt-", "", ".scope", "", "\\x2d", "-")
                        pod := replacer.Replace(splits[2])
                        pod = strings.Replace(pod, "machine-rkt-", "", -1)
                        if len(splits) == 3 {
                                return pod, nil
                        }
                        if splits[3] == "system.slice" {
                                container := strings.Replace(splits[4], ".service", "", -1)
                                return pod + ":" + container, nil
                        }
                }
        }

        return "", fmt.Errorf("%s not handled by rkt handler", name)
}

the strings.Replace for pod shouldn't be necessary, I'd expect the replacer to work correctly, but it doesn't. Either it's buggy or i'm using it incorrectly, but I don't know what I'm doing wrong.

can duplicate with https://play.golang.org/p/p_akq9d3YW by playing with comenting out line 18

[mdempsky]

I think this is a more minimal example of your issue report: http://play.golang.org/p/EaTEE0Z3vj

s := "ab"
r := strings.NewReplacer("aa", "c", "b", "a")
fmt.Println(r.Replace(s))

Basically you're expecting this to replace the "b" with "a", and then to backtrack and replace the "aa" with "c".

However, the documentation for strings.NewReplacer says "Replacements are performed in order, without overlapping matches." So I don't think your expectation is sound.

If I've misunderstood, feel free to clarify. Thanks!

[sjpotter]

I agree, in rereading my issue and looking at the variable, I now see the problem, the - after rkt isn't a dash, it's a \x2d. This goes to mangling that I'm trying to work around.