status: print module info details

fixes https://github.com/gokrazy/gokrazy/issues/59

assets/status.tmpl

@@ -25,6 +25,9 @@
 </tr>
 </table>
 
+  <h3>module info</h3>
+  <pre>{{ .Service.ModuleInfo }}</pre>
+
   <h3>stdout</h3>
   <pre>
   {{ range $idx, $line := .Service.Stdout.Lines -}}

go.mod

@@ -12,4 +12,5 @@ require (
 	github.com/stretchr/testify v1.5.1 // indirect
 	golang.org/x/crypto v0.0.0-20191206172530-e9b2fee46413
 	golang.org/x/sys v0.0.0-20200406155108-e3b113bbe6a4
+	rsc.io/goversion v1.2.0
 )

go.sum

@@ -35,3 +35,5 @@ gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405 h1:yhCVgyC4o1eVCa2tZl7eS0r+
 gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
 gopkg.in/yaml.v2 v2.2.2 h1:ZCJp+EgiOT7lHqUV2J862kp8Qj64Jo6az82+3Td9dZw=
 gopkg.in/yaml.v2 v2.2.2/go.mod h1:hI93XBmqTisBFMUTm0b8Fm+jr3Dg1NNxqwp+5A1VGuI=
+rsc.io/goversion v1.2.0 h1:SPn+NLTiAG7w30IRK/DKp1BjvpWabYgxlLp/+kx5J8w=
+rsc.io/goversion v1.2.0/go.mod h1:Eih9y/uIBS3ulggl7KNJ09xGSLcuNaLgmvvqa07sgfo=

status.go

@@ -17,6 +17,7 @@ import (
 
 	"github.com/gokrazy/gokrazy/internal/bundled"
 	"github.com/gokrazy/internal/rootdev"
+	"rsc.io/goversion/version"
 
 	"golang.org/x/sys/unix"
 )
@@ -123,6 +124,23 @@ func model() string {
 	return strings.TrimSpace(model)
 }
 
+func readModuleInfo(path string) (string, error) {
+	v, err := version.ReadExe(path)
+	if err != nil {
+		return "", err
+	}
+	lines := strings.Split(strings.TrimSpace(v.ModuleInfo), "\n")
+	shortened := make([]string, len(lines))
+	for idx, line := range lines {
+		row := strings.Split(line, "\t")
+		if len(row) > 3 {
+			row = row[:3]
+		}
+		shortened[idx] = strings.Join(row, "\t")
+	}
+	return strings.Join(shortened, "\n"), nil
+}
+
 func initStatus(services []*service) {
 	model := model()
 

supervise.go

@@ -129,6 +129,10 @@ type lineswriter interface {
 }
 
 type service struct {
+	// config (never updated)
+	ModuleInfo string
+
+	// state
 	stopped   bool
 	stoppedMu sync.RWMutex
 	cmd       *exec.Cmd
@@ -258,6 +262,12 @@ func isDontSupervise(err error) bool {
 
 func supervise(s *service) {
 	tag := filepath.Base(s.cmd.Path)
+	if modInfo, err := readModuleInfo(s.cmd.Path); err == nil {
+		s.ModuleInfo = modInfo
+	} else {
+		log.Printf("cannot read module info from %s: %v", s.cmd.Path, err)
+	}
+
 	s.Stdout = newLogWriter(tag)
 	s.Stderr = newLogWriter(tag)
 	l := log.New(s.Stderr, "", log.LstdFlags|log.Ldate|log.Ltime)