StringToSliceHookFunc adds TrimSpace to handle the problem of spaces before and after array strings

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Problem Description

For example add this hook StringToSliceHookFunc(",") to viper, only handle this array string "a,b,c,d", can't handle "a, b, c, d", but in the same service, a viper will handle these two different formats
https://github.com/urfave/cli have resolve this problem, refer to https://github.com/urfave/cli/blob/e8abd76fa3ee5f1bacb52eab9b71dedbeab41991/flag_slice_base.go#L61

Proposed Solution

Use TrimSpace trim items in string array, and also can trim other space defined by Unicode.

func StringToSliceHookFunc(sep string) mapstructure.DecodeHookFunc {
    return func(
        f reflect.Kind,
        t reflect.Kind,
        data interface{}) (interface{}, error) {
        if f != reflect.String || t != reflect.Slice {
            return data, nil
        }

        raw := data.(string)
        if raw == "" {
            return []string{}, nil
        }

        var strs []string
        for _, s := range strings.Split(raw, sep) {
            s = strings.TrimSpace(s)
            strs = append(strs, s)
        }

        return strs, nil
    }
}

Alternatives Considered

No response

Additional Information

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spf13 / viper

StringToSliceHookFunc adds TrimSpace to handle the problem of spaces before and after array strings #1665

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Problem Description

Proposed Solution

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Additional Information