subproc: lazy lookup nomad binary in self call (#20231)

helper/subproc/self.go

@@ -8,30 +8,31 @@ import (
 	"os"
 	"os/exec"
 	"strings"
+	"sync"
 )
 
 var (
 	// executable is the executable of this process
 	executable string
+	once       sync.Once
 )
 
-func init() {
-	s, err := os.Executable()
-	if err != nil {
-		panic(fmt.Sprintf("failed to detect executable: %v", err))
-	}
-
-	// when running tests, we need to use the real nomad binary,
-	// and make sure you recompile between changes!
-	if strings.HasSuffix(s, ".test") {
-		if s, err = exec.LookPath("nomad"); err != nil {
-			panic(fmt.Sprintf("failed to find nomad binary: %v", err))
-		}
-	}
-	executable = s
-}
-
 // Self returns the path to the executable of this process.
 func Self() string {
+	once.Do(func() {
+		s, err := os.Executable()
+		if err != nil {
+			panic(fmt.Sprintf("failed to detect executable: %v", err))
+		}
+
+		// when running tests, we need to use the real nomad binary,
+		// and make sure you recompile between changes!
+		if strings.HasSuffix(s, ".test") {
+			if s, err = exec.LookPath("nomad"); err != nil {
+				panic(fmt.Sprintf("failed to find nomad binary: %v", err))
+			}
+		}
+		executable = s
+	})
 	return executable
 }

helper/subproc/self_test.go

@@ -0,0 +1,15 @@
+// Copyright (c) HashiCorp, Inc.
+// SPDX-License-Identifier: BUSL-1.1
+
+package subproc
+
+import (
+	"testing"
+
+	"github.com/shoenig/test/must"
+)
+
+func TestSelf(t *testing.T) {
+	value := Self()
+	must.NotEq(t, "", value)
+}