From 626ee3faed6d2cdc04bb0f6735a5303efc33b8a3 Mon Sep 17 00:00:00 2001
From: hc-github-team-nomad-core
 <82989552+hc-github-team-nomad-core@users.noreply.github.com>
Date: Thu, 8 Dec 2022 12:09:52 -0500
Subject: [PATCH] backport of commit 8d30bc6537c193231dd07ce453ab0656897f0b94
 (#15502)

This pull request was automerged via backport-assistant
---
 helper/pointer/pointer.go      | 16 ++++++++++++----
 helper/pointer/pointer_test.go | 27 +++++++++++++++++++++++++++
 2 files changed, 39 insertions(+), 4 deletions(-)

diff --git a/helper/pointer/pointer.go b/helper/pointer/pointer.go
index 0e806c0bbb1..2e3fc8d4119 100644
--- a/helper/pointer/pointer.go
+++ b/helper/pointer/pointer.go
@@ -5,6 +5,12 @@ import (
 	"golang.org/x/exp/constraints"
 )
 
+// Primitive represents basic types that are safe to do basic comparisons by
+// pointer dereference (checking nullity first).
+type Primitive interface {
+	constraints.Ordered | bool
+}
+
 // Of returns a pointer to a.
 func Of[A any](a A) *A {
 	return &a
@@ -19,10 +25,12 @@ func Copy[A any](a *A) *A {
 	return &na
 }
 
-// Primitive represents basic types that are safe to do basic comparisons by
-// pointer dereference (checking nullity first).
-type Primitive interface {
-	constraints.Ordered // just so happens to be the types we want
+// Merge will return Copy(next) if next is not nil, otherwise return Copy(previous).
+func Merge[P Primitive](previous, next *P) *P {
+	if next != nil {
+		return Copy(next)
+	}
+	return Copy(previous)
 }
 
 // Eq returns whether a and b are equal in underlying value.
diff --git a/helper/pointer/pointer_test.go b/helper/pointer/pointer_test.go
index fca66483474..4cef8b5d568 100644
--- a/helper/pointer/pointer_test.go
+++ b/helper/pointer/pointer_test.go
@@ -4,10 +4,13 @@ import (
 	"testing"
 	"time"
 
+	"github.com/hashicorp/nomad/ci"
 	"github.com/shoenig/test/must"
 )
 
 func Test_Of(t *testing.T) {
+	ci.Parallel(t)
+
 	s := "hello"
 	sPtr := Of(s)
 
@@ -19,6 +22,8 @@ func Test_Of(t *testing.T) {
 }
 
 func Test_Copy(t *testing.T) {
+	ci.Parallel(t)
+
 	orig := Of(1)
 	dup := Copy(orig)
 	orig = Of(7)
@@ -27,6 +32,8 @@ func Test_Copy(t *testing.T) {
 }
 
 func Test_Compare(t *testing.T) {
+	ci.Parallel(t)
+
 	t.Run("int", func(t *testing.T) {
 		a := 1
 		b := 2
@@ -65,3 +72,23 @@ func Test_Compare(t *testing.T) {
 		must.True(t, Eq(n, nil))
 	})
 }
+
+func Test_Merge(t *testing.T) {
+	ci.Parallel(t)
+	
+	a := 1
+	b := 2
+
+	ptrA := &a
+	ptrB := &b
+
+	t.Run("exists", func(t *testing.T) {
+		result := Merge(ptrA, ptrB)
+		must.Eq(t, 2, *result)
+	})
+
+	t.Run("nil", func(t *testing.T) {
+		result := Merge(ptrA, nil)
+		must.Eq(t, 1, *result)
+	})
+}