Fix: Missing null check in LRU cleanup

acdlite · acdlite · commit f97fa629e96d · 2025-12-12T17:08:34.000-05:00
Unfortunately this field is not strongly typed because it's a cyclic
type and I wasn't able to soundly model it with TypeScript. Skill issue
I'm sure.

Don't have an exact repro yet but the previous code was obviously wrong.

The way this should have been structured regardless is to delete
the wrapper MapEntry object instead of the value it contains. The
non-nullness of the wrapper object _is_ properly typed, and avoids
an unnecessary indirection.

As a follow up, I'll look into how to model this type properly.
diff --git a/packages/next/src/client/components/segment-cache/cache-map.ts b/packages/next/src/client/components/segment-cache/cache-map.ts
@@ -396,7 +396,7 @@ function dropRef<V extends MapValue>(value: V): void {
   value.ref = null
 }
 
-function deleteMapEntry<V extends MapValue>(entry: MapEntry<V>): void {
+export function deleteMapEntry<V extends MapValue>(entry: MapEntry<V>): void {
   // Delete the entry from the cache.
   const emptyEntry: EmptyMapEntry<V> = entry as any
   emptyEntry.value = null
diff --git a/packages/next/src/client/components/segment-cache/lru.ts b/packages/next/src/client/components/segment-cache/lru.ts
@@ -1,5 +1,5 @@
 import type { MapEntry } from './cache-map'
-import { deleteFromCacheMap } from './cache-map'
+import { deleteMapEntry } from './cache-map'
 
 // We use an LRU for memory management. We must update this whenever we add or
 // remove a new cache entry, or when an entry changes size.
@@ -119,7 +119,7 @@ function cleanup() {
     if (tail !== null) {
       // Delete the entry from the map. In turn, this will remove it from
       // the LRU.
-      deleteFromCacheMap(tail.value)
+      deleteMapEntry(tail)
     }
   }
 }

Original file line number	Diff line number	Diff line change
`@@ -396,7 +396,7 @@ function dropRef<V extends MapValue>(value: V): void {`
`396`	`396`	`value.ref = null`
`397`	`397`	`}`
`398`	`398`
`399`		`-function deleteMapEntry<V extends MapValue>(entry: MapEntry<V>): void {`
	`399`	`+export function deleteMapEntry<V extends MapValue>(entry: MapEntry<V>): void {`
`400`	`400`	`// Delete the entry from the cache.`
`401`	`401`	`const emptyEntry: EmptyMapEntry<V> = entry as any`
`402`	`402`	`emptyEntry.value = null`
Original file line number	Diff line number	Diff line change
`@@ -1,5 +1,5 @@`
`1`	`1`	`import type { MapEntry } from './cache-map'`
`2`		`-import { deleteFromCacheMap } from './cache-map'`
	`2`	`+import { deleteMapEntry } from './cache-map'`
`3`	`3`
`4`	`4`	`// We use an LRU for memory management. We must update this whenever we add or`
`5`	`5`	`// remove a new cache entry, or when an entry changes size.`
`@@ -119,7 +119,7 @@ function cleanup() {`
`119`	`119`	`if (tail !== null) {`
`120`	`120`	`// Delete the entry from the map. In turn, this will remove it from`
`121`	`121`	`// the LRU.`
`122`		`- deleteFromCacheMap(tail.value)`
	`122`	`+ deleteMapEntry(tail)`
`123`	`123`	`}`
`124`	`124`	`}`
`125`	`125`	`}`