From 03a86486eabb98988220415834dc9da06abb7d6d Mon Sep 17 00:00:00 2001
From: Wesley Powell <wspowell@users.noreply.github.com>
Date: Fri, 16 Jul 2021 02:41:17 -0500
Subject: [PATCH] Backport wrapMultiExec() cmds copy bug fix from v8 (#1823)

---
 .gitignore       |  1 +
 pipeline_test.go | 17 +++++++++++++++++
 redis.go         | 10 +++++-----
 3 files changed, 23 insertions(+), 5 deletions(-)

diff --git a/.gitignore b/.gitignore
index ebfe903bc..b975a7b4c 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1,2 +1,3 @@
 *.rdb
 testdata/*/
+.idea/
diff --git a/pipeline_test.go b/pipeline_test.go
index fb82e4eb4..a00da7a77 100644
--- a/pipeline_test.go
+++ b/pipeline_test.go
@@ -1,6 +1,8 @@
 package redis_test
 
 import (
+	"strconv"
+
 	"github.com/go-redis/redis/v7"
 
 	. "github.com/onsi/ginkgo"
@@ -67,6 +69,21 @@ var _ = Describe("pipelining", func() {
 			Expect(err).NotTo(HaveOccurred())
 			Expect(cmds).To(HaveLen(1))
 		})
+
+		It("handles large pipelines", func() {
+			for callCount := 1; callCount < 16; callCount++ {
+				for i := 1; i <= callCount; i++ {
+					pipe.SetNX(strconv.Itoa(i)+"_key", strconv.Itoa(i)+"_value", 0)
+				}
+
+				cmds, err := pipe.Exec()
+				Expect(err).NotTo(HaveOccurred())
+				Expect(cmds).To(HaveLen(callCount))
+				for _, cmd := range cmds {
+					Expect(cmd).To(BeAssignableToTypeOf(&redis.BoolCmd{}))
+				}
+			}
+		})
 	}
 
 	Describe("Pipeline", func() {
diff --git a/redis.go b/redis.go
index 3d9dfed7d..ac0569f5a 100644
--- a/redis.go
+++ b/redis.go
@@ -473,11 +473,11 @@ func wrapMultiExec(cmds []Cmder) []Cmder {
 	if len(cmds) == 0 {
 		panic("not reached")
 	}
-	cmds = append(cmds, make([]Cmder, 2)...)
-	copy(cmds[1:], cmds[:len(cmds)-2])
-	cmds[0] = NewStatusCmd("multi")
-	cmds[len(cmds)-1] = NewSliceCmd("exec")
-	return cmds
+	cmdCopy := make([]Cmder, len(cmds)+2)
+	cmdCopy[0] = NewStatusCmd("multi")
+	copy(cmdCopy[1:], cmds)
+	cmdCopy[len(cmdCopy)-1] = NewSliceCmd("exec")
+	return cmdCopy
 }
 
 func txPipelineReadQueued(rd *proto.Reader, statusCmd *StatusCmd, cmds []Cmder) error {