From 9586e3c00a3994386e7b3d7e254eeeaaf5db4a4a Mon Sep 17 00:00:00 2001
From: Seth Hoenig <seth.a.hoenig@gmail.com>
Date: Sat, 13 Aug 2022 09:13:54 -0500
Subject: [PATCH] cleanup: helper funcs for comparing slices of references

---
 helper/funcs.go           | 24 ++++++++++++++++++++++++
 helper/funcs_test.go      | 39 +++++++++++++++++++++++++++++++++++++++
 nomad/structs/services.go | 15 +--------------
 3 files changed, 64 insertions(+), 14 deletions(-)

diff --git a/helper/funcs.go b/helper/funcs.go
index ec3842f4c..8b5137cad 100644
--- a/helper/funcs.go
+++ b/helper/funcs.go
@@ -735,3 +735,27 @@ func IsMethodHTTP(s string) bool {
 	}
 	return true
 }
+
+// EqualsFunc represents a type implementing the Equals method.
+type EqualsFunc[A any] interface {
+	Equals(A) bool
+}
+
+// ElementsEquals returns true if slices a and b contain the same elements (in
+// no particular order) using the Equals function defined on their type for
+// comparison.
+func ElementsEquals[T EqualsFunc[T]](a, b []T) bool {
+	if len(a) != len(b) {
+		return false
+	}
+OUTER:
+	for _, item := range a {
+		for _, other := range b {
+			if item.Equals(other) {
+				continue OUTER
+			}
+		}
+		return false
+	}
+	return true
+}
diff --git a/helper/funcs_test.go b/helper/funcs_test.go
index 79fd90026..977454bcd 100644
--- a/helper/funcs_test.go
+++ b/helper/funcs_test.go
@@ -574,3 +574,42 @@ func Test_IsMethodHTTP(t *testing.T) {
 		}
 	})
 }
+
+type employee struct {
+	id   int
+	name string
+}
+
+func (e *employee) Equals(o *employee) bool {
+	return e.id == o.id // name can be different
+}
+
+func Test_ElementsEquals(t *testing.T) {
+	t.Run("empty", func(t *testing.T) {
+		a := []*employee(nil)
+		var b []*employee
+		must.True(t, ElementsEquals(a, b))
+		must.True(t, ElementsEquals(b, a))
+	})
+
+	t.Run("different sizes", func(t *testing.T) {
+		a := []*employee{{1, "mitchell"}, {2, "armon"}, {3, "jack"}}
+		b := []*employee{{1, "mitchell"}, {2, "armon"}}
+		must.False(t, ElementsEquals(a, b))
+		must.False(t, ElementsEquals(b, a))
+	})
+
+	t.Run("equal", func(t *testing.T) {
+		a := []*employee{{1, "mitchell"}, {2, "armon"}, {3, "jack"}}
+		b := []*employee{{1, "M.H."}, {2, "A.D."}, {3, "J.P."}}
+		must.True(t, ElementsEquals(a, b))
+		must.True(t, ElementsEquals(b, a))
+	})
+
+	t.Run("different", func(t *testing.T) {
+		a := []*employee{{1, "mitchell"}, {2, "armon"}, {3, "jack"}}
+		b := []*employee{{0, "mitchell."}, {2, "armon"}, {3, "jack"}}
+		must.False(t, ElementsEquals(a, b))
+		must.False(t, ElementsEquals(b, a))
+	})
+}
diff --git a/nomad/structs/services.go b/nomad/structs/services.go
index 229023340..822414cc2 100644
--- a/nomad/structs/services.go
+++ b/nomad/structs/services.go
@@ -905,20 +905,7 @@ func (s *Service) Equals(o *Service) bool {
 		return false
 	}
 
-	if len(s.Checks) != len(o.Checks) {
-		return false
-	}
-
-OUTER:
-	for i := range s.Checks {
-		for ii := range o.Checks {
-			if s.Checks[i].Equals(o.Checks[ii]) {
-				// Found match; continue with next check
-				continue OUTER
-			}
-		}
-
-		// No match
+	if !helper.ElementsEquals(s.Checks, o.Checks) {
 		return false
 	}