fixup! fix(vow): handle resolution loops in vows

make watch cycle detection ephemeral
Agoric · Jun 21, 2024 · 5bdad2c · 5bdad2c
1 parent a6c378f
commit 5bdad2c
Showing 1 changed file with 24 additions and 6 deletions.
diff --git a/packages/vow/src/watch.js b/packages/vow/src/watch.js
@@ -65,8 +65,23 @@ const settle = (resolver, watcher, wcb, value, watcherArgs = []) => {
  * @param {IsRetryableReason} isRetryableReason
  * @param {ReturnType<typeof makeWatchNextStep>} watchNextStep
  */
-const preparePromiseWatcher = (zone, isRetryableReason, watchNextStep) =>
-  zone.exoClass(
+const preparePromiseWatcher = (zone, isRetryableReason, watchNextStep) => {
+  // We use an ephemeral WeakSet for the previously seen vows in a watch operation
+  // While watch is durable, it suffices to detect the cycle in a single incarnation
+  /** @type {WeakMap<PromiseWatcher, WeakSet<any>>} */
+  const watcherSeenPayloads = new WeakMap();
+
+  /** @param {PromiseWatcher} watcher */
+  const getSeenPayloads = watcher => {
+    let seenPayloads = watcherSeenPayloads.get(watcher);
+    if (!seenPayloads) {
+      seenPayloads = new WeakSet();
+      watcherSeenPayloads.set(watcher, seenPayloads);
+    }
+    return seenPayloads;
+  };
+
+  return zone.exoClass(
     'PromiseWatcher',
     PromiseWatcherI,
     /**
@@ -81,7 +96,6 @@ const preparePromiseWatcher = (zone, isRetryableReason, watchNextStep) =>
       const state = {
         vow: /** @type {unknown} */ (undefined),
         priorRetryValue: /** @type {any} */ (undefined),
-        seenPayloads: zone.detached().weakSetStore('seenPayloads'),
         resolver,
         watcher,
         watcherArgs: harden(watcherArgs),
@@ -91,19 +105,21 @@ const preparePromiseWatcher = (zone, isRetryableReason, watchNextStep) =>
     {
       /** @type {Required<PromiseWatcher>['onFulfilled']} */
       onFulfilled(value) {
-        const { watcher, watcherArgs, resolver, seenPayloads } = this.state;
+        const { watcher, watcherArgs, resolver } = this.state;
         const payload = getVowPayload(value);
         if (payload) {
+          const seenPayloads = getSeenPayloads(this.self);
           // TODO: rely on endowed helper to get storable cap from payload
-          if (seenPayloads?.has(payload.vowV0)) {
+          if (seenPayloads.has(payload.vowV0)) {
             return this.self.onRejected(Error('Vow resolution cycle detected'));
           }
-          seenPayloads?.add(payload.vowV0);
+          seenPayloads.add(payload.vowV0);
           // We've been shortened, so reflect our state accordingly, and go again.
           this.state.vow = value;
           watchNextStep(value, this.self);
           return;
         }
+        watcherSeenPayloads.delete(this.self);
         this.state.priorRetryValue = undefined;
         this.state.watcher = undefined;
         this.state.resolver = undefined;
@@ -122,13 +138,15 @@ const preparePromiseWatcher = (zone, isRetryableReason, watchNextStep) =>
             return;
           }
         }
+        watcherSeenPayloads.delete(this.self);
         this.state.priorRetryValue = undefined;
         this.state.resolver = undefined;
         this.state.watcher = undefined;
         settle(resolver, watcher, 'onRejected', reason, watcherArgs);
       },
     },
   );
+};
 
 /**
  * @param {Zone} zone