Generate prerelease versions

Signed-off-by: Dave Henderson <dhenderson@gmail.com>

2 files changed, 146 insertions, 0 deletions

diff --git a/version/gen/vgen.go b/version/gen/vgen.go
new file mode 100644
index 00000000..c6c1913b
--- /dev/null
+++ b/version/gen/vgen.go
@@ -0,0 +1,115 @@
+// run as 'go run ./version/gen/vgen.go'
+
+package main
+
+import (
+	"fmt"
+	"log"
+	"os/exec"
+	"strings"
+
+	"github.com/Masterminds/semver"
+)
+
+func main() {
+	descVer, err := describedVersion()
+	if err != nil {
+		log.Fatal(err)
+	}
+
+	latest, err := latestTag()
+	if err != nil {
+		log.Fatal(err)
+	}
+
+	ver, err := version(descVer, latest)
+	if err != nil {
+		log.Fatal(err)
+	}
+
+	fmt.Println(ver.String())
+}
+
+func describedVersion() (*semver.Version, error) {
+	desc, err := runCmd("git describe --always")
+	if err != nil {
+		return nil, fmt.Errorf("git describe failed: %w", err)
+	}
+
+	ver, err := semver.NewVersion(desc)
+	if err != nil {
+		return nil, err
+	}
+
+	return ver, nil
+}
+
+func version(descVer, latest *semver.Version) (*semver.Version, error) {
+	ver := *descVer
+	if ver.Prerelease() != "" {
+		ver = ver.IncPatch().IncPatch()
+		ver, _ = ver.SetPrerelease(descVer.Prerelease())
+		ver, _ = ver.SetMetadata(descVer.Metadata())
+	} else if ver.Metadata() != "" {
+		ver = ver.IncPatch()
+		ver, _ = ver.SetMetadata(descVer.Metadata())
+	}
+
+	// if we're on a release tag already, we're done
+	if descVer.Equal(&ver) {
+		return descVer, nil
+	}
+
+	// If 'latest' is greater than 'ver', we need to skip to the next patch.
+	// If 'latest' is already a prerelease (i.e. if v5.0.0-pre was tagged),
+	// we should use
+	// If 'latest' is a prerelease, it's the same logic, except that we don't
+	// want to increment the patch version.
+	if latest.GreaterThan(&ver) || latest.Prerelease() != "" {
+		v := *latest
+		if v.Prerelease() == "" {
+			v = v.IncPatch()
+		}
+		v, _ = v.SetPrerelease(ver.Prerelease())
+		v, _ = v.SetMetadata(ver.Metadata())
+
+		ver = v
+	}
+
+	return &ver, nil
+}
+
+func latestTag() (*semver.Version, error) {
+	// get the latest tag
+	tags, err := runCmd("git tag --list v*")
+	if err != nil {
+		return nil, fmt.Errorf("git tag failed: %w", err)
+	}
+
+	// find the latest tag
+	var latest *semver.Version
+	for _, tag := range strings.Split(tags, "\n") {
+		ver, err := semver.NewVersion(tag)
+		if err != nil {
+			return nil, fmt.Errorf("parsing tag %q failed: %w", tag, err)
+		}
+
+		if latest == nil || ver.GreaterThan(latest) {
+			latest = ver
+		}
+	}
+
+	if latest == nil {
+		return nil, fmt.Errorf("no tags found")
+	}
+
+	return latest, nil
+}
+
+func runCmd(c string) (string, error) {
+	parts := strings.Split(c, " ")
+	//nolint:gosec
+	cmd := exec.Command(parts[0], parts[1:]...)
+	out, err := cmd.CombinedOutput()
+	return strings.TrimSpace(string(out)), err
+}
diff --git a/version/gen/vgen_test.go b/version/gen/vgen_test.go
new file mode 100644
index 00000000..2bbc3e3a
--- /dev/null
+++ b/version/gen/vgen_test.go
@@ -0,0 +1,31 @@
+package main
+
+import (
+	"testing"
+
+	"github.com/Masterminds/semver"
+	"github.com/stretchr/testify/require"
+)
+
+func TestVersion(t *testing.T) {
+	testdata := []struct {
+		desc, latest string
+		expected     string
+	}{
+		{"v1.0.0", "", "1.0.0"},
+		{"v1.0.0-1-gabcdef0", "v1.0.0", "1.0.1-1-gabcdef0"},
+		{"v1.0.0-1-gabcdef0", "v2.3.4", "2.3.5-1-gabcdef0"},
+		{"v1.0.0+123", "v2.3.4", "2.3.5+123"},
+	}
+
+	for _, td := range testdata {
+		var l *semver.Version
+		if td.latest != "" {
+			l = semver.MustParse(td.latest)
+		}
+
+		ver, err := version(semver.MustParse(td.desc), l)
+		require.NoError(t, err)
+		require.Equal(t, td.expected, ver.String())
+	}
+}