Constraint check fails for .0 patch prereleases

[johanneskra]

I think I have found a bug in the constraint check for .0 patch prereleases.

An example for this can be found in the Go Playground https://go.dev/play/p/LShjC5F37TT or in the main.go:

main.go (expand)

package main

import (
  "fmt"

  "github.com/blang/semver/v4"
)

func main() {
  constraint := "0.49.x"
  versionConstraint, err := semver.ParseRange(constraint)
  if err != nil {
  	return
  }

  versions := []string{
  	"0.49.0-alpha",
  	"0.49.1-alpha",
  	"0.49.0",
  	"0.49.1",
  }

  for _, ver := range versions {
  	parsedVersion, err := semver.Parse(ver)
  	if err != nil {
  		return
  	}

  	fmt.Printf("%v becomes:\n %#v \n", ver, parsedVersion)
  	fmt.Printf(" Major: %d\n", parsedVersion.Major)
  	fmt.Printf(" Minor: %d\n", parsedVersion.Minor)
  	fmt.Printf(" Patch: %d\n", parsedVersion.Patch)
  	fmt.Printf(" Pre: %s\n", parsedVersion.Pre)
  	fmt.Printf(" Build: %s\n", parsedVersion.Build)

  	didMatch := "false"
  	if versionConstraint(parsedVersion) {
  		didMatch = "true"
  	}

  	fmt.Printf(" => constraint %v matched for %v: %v \n\n", constraint, ver, didMatch)
  }

}

The output of this is:

0.49.0-alpha becomes:
 semver.Version{Major:0x0, Minor:0x31, Patch:0x0, Pre:[]semver.PRVersion{semver.PRVersion{VersionStr:"alpha", VersionNum:0x0, IsNum:false}}, Build:[]string(nil)} 
 Major: 0
 Minor: 49
 Patch: 0
 Pre: [alpha]
 Build: []
 => constraint 0.49.x matched for 0.49.0-alpha: false // ❌ this seems to be a bug

0.49.1-alpha becomes:
 semver.Version{Major:0x0, Minor:0x31, Patch:0x1, Pre:[]semver.PRVersion{semver.PRVersion{VersionStr:"alpha", VersionNum:0x0, IsNum:false}}, Build:[]string(nil)} 
 Major: 0
 Minor: 49
 Patch: 1
 Pre: [alpha]
 Build: []
 => constraint 0.49.x matched for 0.49.1-alpha: true  // ✅ as expected 

0.49.0 becomes:
 semver.Version{Major:0x0, Minor:0x31, Patch:0x0, Pre:[]semver.PRVersion(nil), Build:[]string(nil)} 
 Major: 0
 Minor: 49
 Patch: 0
 Pre: []
 Build: []
 => constraint 0.49.x matched for 0.49.0: true // ✅ as expected 

0.49.1 becomes:
 semver.Version{Major:0x0, Minor:0x31, Patch:0x1, Pre:[]semver.PRVersion(nil), Build:[]string(nil)} 
 Major: 0
 Minor: 49
 Patch: 1
 Pre: []
 Build: []
 => constraint 0.49.x matched for 0.49.1: true // ✅ as expected 

According to this SemVer check, that's incorrect: https://jubianchi.github.io/semver-check/#/0.49.x/0.49.0-alpha.