From fd641679615e5c74f196c6bc7688b3d04c9a0a41 Mon Sep 17 00:00:00 2001
From: Michael FIG <mfig@agoric.com>
Date: Tue, 21 Mar 2023 14:20:48 -0600
Subject: [PATCH] fixup! fix(ses): avoid holding deep stacks strongly

---
 packages/ses/src/error/note-log-args.js | 20 ++++++++++++--------
 1 file changed, 12 insertions(+), 8 deletions(-)

diff --git a/packages/ses/src/error/note-log-args.js b/packages/ses/src/error/note-log-args.js
index 347e648236..8ad8329b32 100644
--- a/packages/ses/src/error/note-log-args.js
+++ b/packages/ses/src/error/note-log-args.js
@@ -96,7 +96,7 @@ const spliceOut = cell => {
  * bookkeeping cell has not been pushed off the end of the cache by `budget`
  * number of more recently referenced cells.  If the key is dropped by the user,
  * the value will no longer be held by the cache, but the bookkeeping cell
- * itself vill stay in memory until it has cycled off the end of the cache.
+ * itself will stay in memory.
  *
  * @template {{}} K
  * @template {unknown} V
@@ -107,11 +107,12 @@ export const makeLRUCacheMap = budget => {
   if (!isSafeInteger(budget) || budget < 0) {
     throw new TypeError('budget must be a safe non-negative integer number');
   }
-  /** @type {WeakMap<K, DoublyLinkedCell<WeakMap<K, V> | undefined>>} */
+  /** @typedef {DoublyLinkedCell<WeakMap<K, V> | undefined>} LRUCacheCell */
+  /** @type {WeakMap<K, LRUCacheCell>} */
   const keyToCell = new WeakMap();
   let size = 0; // `size` must remain <= `budget`
   // As a sigil, `head` uniquely is not in the `keyToCell` map.
-  /** @type {DoublyLinkedCell<WeakMap<K, V> | undefined>} */
+  /** @type {LRUCacheCell>} */
   const head = makeSelfCell(undefined);
 
   const touchCell = key => {
@@ -136,7 +137,7 @@ export const makeLRUCacheMap = budget => {
    */
   // TODO Change to the following line, once our tools don't choke on `?.`.
   // See https://github.com/endojs/endo/issues/1514
-  // const get = key => touchCell(key)?.keyValue.get(key);
+  // const get = key => touchCell(key)?.data?.get(key);
   const get = key => {
     const cell = touchCell(key);
     return cell && cell.data && cell.data.get(key);
@@ -149,7 +150,7 @@ export const makeLRUCacheMap = budget => {
    */
   const set = (key, value) => {
     if (budget >= 1) {
-      /** @type {DoublyLinkedCell<WeakMap<K, V> | undefined> | undefined} */
+      /** @type {LRUCacheCell | undefined} */
       let cell = touchCell(key);
       if (cell === undefined) {
         if (size >= budget) {
@@ -159,13 +160,16 @@ export const makeLRUCacheMap = budget => {
           size -= 1;
         }
         size += 1;
-        cell = makeSelfCell(new WeakMap());
-        keyToCell.set(key, cell);
+        cell = makeSelfCell(undefined);
         spliceAfter(head, cell); // start most recently used
       }
       if (!cell.data) {
-        throw TypeError('Internal error; expected cell.data');
+        // Either a new cell or a condemned cell.  Add its data.
+        cell.data = new WeakMap();
+        // Advertise the cell for this key.
+        keyToCell.set(key, cell);
       }
+      // Update the data.
       cell.data.set(key, value);
     }
     // eslint-disable-next-line no-use-before-define