Golang正则表达式与`ReplaceAllString`多次匹配

Question

I am trying to write some regular expressions that match and pull apart strings that look like software versions (but they aren't really, so semver parsing, for instance, won't work). I'm having some trouble matching what I am calling "prefix" and "suffix" parts of the input string.

The output I am getting from the following is, strange..

// Sample inputs:
// * '1.2.3-thing' (Prefix: '1.2.3', Suffix: '-thing')
// * '1.2.3+1' (Prefix: '1.2.3', Suffix: '+1')
// * '1.2.3' (Prefix: '1.2.3', Suffix: '')
// * '1' (Prefix: '1', Suffix: '')
// * '1-x' (Prefix: '1', Suffix: '-x')
// * '1-x-x' (Prefix: '1', Suffix: '-x-x')
// * '1.2.3-thing.1' (Prefix: '1.2.3', Suffix: '-thing.1')
// * '1.2-thing-1' (Prefix: '1.2', Suffix: '-thing-1')
// * 'k1.2.3-thing' (Prefix: 'k1.2.3', Suffix: '-thing')
// * 'k-thing-x' (Prefix: 'k', Suffix: '-thing-x')
//
func InspectVersionTag(tag string) {
    re := regexp.MustCompile(`^([^\-]+)([\-+].+)$`)
    suffix := ""
    if re.MatchString(tag) {
        tag = re.ReplaceAllString(tag, `$1`)
        suffix = re.ReplaceAllString(tag, `$2`)
    }
    fmt.Println(fmt.Sprintf("Prefix is: %s", tag))
    fmt.Println(fmt.Sprintf("Suffix is: %s", suffix))
}

// Current sample output
//
// Input: 1.2.3+1
// Prefix is: 1.2.3
// Suffix is: 1.2.3

Answer 1

Regexp is the wrong tool for this simple task, because it is slow, difficult to read, and as this question indicates, difficult to reason about. For these same reasons, regexp is the wrong tool for almost all tasks it is used for.

In your case, all you need to do is just split on your separators: - and +:

func InspectVersionTag(tag string) {
    var suffix string
    for _, sep := range []string{"-","+"} {
        if strings.Contains(tag, sep) {
            parts := strings.SplitN(tag, sep, 2)
            tag, suffix = parts[0], sep+parts[1]
            continue
        }
    }
    fmt.Printf("Prefix: %s Suffix: %s
", tag, suffix)
}

See playground link.