test(redis): paginate SCAN in the Clear failure test

miniredis 2.39 ignores the SCAN COUNT hint and returns every key in one
batch. The test now paginates SCAN in its own hook, so it no longer
depends on miniredis batching.

cache/redis/redis_clear_glob_test.go

@@ -2,6 +2,8 @@ package libpack_cache_redis
 
 import (
 	"fmt"
+	"sort"
+	"strconv"
 	"sync/atomic"
 	"testing"
 
@@ -125,19 +127,9 @@ func TestClear_NormalPrefix_StillClearsAllOwnedKeys(t *testing.T) {
 // intercept DEL commands without a rewrite of RedisConfig into an
 // interface-backed mock, which the task's infra allows.
 //
-// Every DEL call is made to fail (not just one). A test that lets only one
-// batch's DEL succeed was tried first, and does not work against miniredis:
-// its SCAN implementation uses an index-based cursor over a sorted key
-// snapshot (cmd_generic.go cmdScan), which is invalidated as soon as a
-// preceding batch actually deletes keys mid-scan (the very "scan, then
-// delete this batch" loop Clear uses), causing miniredis to abort the SCAN
-// early with a synthetic empty result before Clear's loop reaches the next
-// batch. Real Redis's SCAN cursor (reverse binary iteration) is documented
-// to be robust against concurrent deletion during a single full iteration
-// and would not exhibit this; it is a miniredis simplification, not a
-// RedisConfig defect. Failing every batch's DEL sidesteps it (no batch is
-// ever actually deleted, so the key set never shrinks between scans) while
-// still proving Clear does not stop scanning after the first DEL error.
+// Every DEL call is made to fail so the key set never shrinks between
+// scans. SCAN is paginated by the hook itself because miniredis ignores
+// COUNT and returns every key in one batch.
 func TestClear_AllBatchesDelFail_AttemptsEveryBatchAndAggregatesErrors(t *testing.T) {
 	s, err := miniredis.Run()
 	require.NoError(t, err)
@@ -146,10 +138,7 @@ func TestClear_AllBatchesDelFail_AttemptsEveryBatchAndAggregatesErrors(t *testin
 	rc, err := New(&RedisClientConfig{RedisServer: s.Addr(), Prefix: "pfx:"})
 	require.NoError(t, err)
 
-	// miniredis SCAN batches deterministically by COUNT over the sorted,
-	// match-filtered key set (see cmd_generic.go cmdScan), so 250 owned keys
-	// with a SCAN COUNT of 100 (as used by Clear) yields exactly 3 batches:
-	// [0:100), [100:200), [200:250).
+	// 250 owned keys with a SCAN page size of 100 yield exactly 3 batches.
 	const totalKeys = 250
 	const wantBatches = 3
 	for i := 0; i < totalKeys; i++ {
@@ -158,7 +147,26 @@ func TestClear_AllBatchesDelFail_AttemptsEveryBatchAndAggregatesErrors(t *testin
 	}
 
 	var seen int32
-	s.Server().SetPreHook(func(c *miniredis_server.Peer, cmd string, _ ...string) bool {
+	const scanPage = 100
+	s.Server().SetPreHook(func(c *miniredis_server.Peer, cmd string, args ...string) bool {
+		if cmd == "SCAN" {
+			cursor, convErr := strconv.Atoi(args[0])
+			if convErr != nil {
+				c.WriteError("ERR invalid cursor")
+				return true
+			}
+			keys := s.Keys()
+			sort.Strings(keys)
+			end := min(cursor+scanPage, len(keys))
+			next := end
+			if end == len(keys) {
+				next = 0
+			}
+			c.WriteLen(2)
+			c.WriteBulk(strconv.Itoa(next))
+			c.WriteStrings(keys[cursor:end])
+			return true
+		}
 		if cmd != "DEL" {
 			return false // let miniredis handle everything else normally
 		}