From e7d1538a2d344b58ee2dc20cb24a4c0cada59d51 Mon Sep 17 00:00:00 2001
From: Brad Fitzpatrick <bradfitz@tailscale.com>
Date: Sun, 27 Aug 2023 16:32:06 -0700
Subject: [PATCH] types/views: add SliceEqual, like std slices.Equal

Updates tailscale/corp#6198

Change-Id: I38614a4552c9fa933036aa493c7cdb57c7ffe2d2
Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com>
---
 types/views/views.go      |  6 ++++++
 types/views/views_test.go | 14 ++++++++++++++
 2 files changed, 20 insertions(+)

diff --git a/types/views/views.go b/types/views/views.go
index 3a802a09c..117e80adc 100644
--- a/types/views/views.go
+++ b/types/views/views.go
@@ -10,6 +10,7 @@ import (
 	"encoding/json"
 	"errors"
 	"maps"
+	"slices"
 
 	"go4.org/mem"
 )
@@ -275,6 +276,11 @@ func SliceContains[T comparable](v Slice[T], e T) bool {
 	return false
 }
 
+// SliceEqual is like the standard library's slices.Equal, but for two views.
+func SliceEqual[T comparable](a, b Slice[T]) bool {
+	return slices.Equal(a.ж, b.ж)
+}
+
 // SliceEqualAnyOrder reports whether a and b contain the same elements, regardless of order.
 // The underlying slices for a and b can be nil.
 func SliceEqualAnyOrder[T comparable](a, b Slice[T]) bool {
diff --git a/types/views/views_test.go b/types/views/views_test.go
index c04eef62b..93cda30e5 100644
--- a/types/views/views_test.go
+++ b/types/views/views_test.go
@@ -150,3 +150,17 @@ func TestLenIter(t *testing.T) {
 		t.Errorf("got %q; want %q", got, orig)
 	}
 }
+
+func TestSliceEqual(t *testing.T) {
+	a := SliceOf([]string{"foo", "bar"})
+	b := SliceOf([]string{"foo", "bar"})
+	if !SliceEqual(a, b) {
+		t.Errorf("got a != b")
+	}
+	if !SliceEqual(a.SliceTo(0), b.SliceTo(0)) {
+		t.Errorf("got a[:0] != b[:0]")
+	}
+	if SliceEqual(a.SliceTo(2), a.SliceTo(1)) {
+		t.Error("got a[:2] == a[:1]")
+	}
+}