fix: durable approach to watching purse balances

packages/boot/test/bootstrapTests/test-wallet-upgrade.js

@@ -115,7 +115,7 @@ test('update purse balance across zoe upgrade', async t => {
         consume: { namesByAddressAdmin: true, zoe: true },
         instance: { consume: { reserve: true } },
       }),
-      js_code: `(${sendInvitationScript})()`,
+      js_code: `(${sendInvitationScript})()`.replace('ADDRESS', oraAddr),
     },
   ]);
 
@@ -152,7 +152,7 @@ test('update purse balance across walletFactory upgrade', async t => {
         consume: { namesByAddressAdmin: true, zoe: true },
         instance: { consume: { reserve: true } },
       }),
-      js_code: `(${sendInvitationScript})()`,
+      js_code: `(${sendInvitationScript})()`.replace('ADDRESS', oraAddr),
     },
   ]);
 

packages/boot/test/bootstrapTests/wallet-scripts.js

@@ -61,7 +61,7 @@ export const restartWalletFactoryScript = () => {
 };
 
 export const sendInvitationScript = () => {
-  const addr = 'agoric1oracle-operator';
+  const addr = 'ADDRESS';
   const sendIt = async powers => {
     // namesByAddress is broken #8113
     const {

packages/smart-wallet/src/smartWallet.js

@@ -22,8 +22,10 @@ import {
 import {
   makeScalarBigMapStore,
   makeScalarBigWeakMapStore,
+  prepareExoClass,
   prepareExoClassKit,
   provide,
+  watchPromise,
 } from '@agoric/vat-data';
 import {
   prepareRecorderKit,
@@ -44,24 +46,6 @@ const { Fail, quote: q } = assert;
 
 const trace = makeTracer('SmrtWlt');
 
-/**
- * Like `subscribeLatest` but that one swallows the upgrade error that this module needs to detect and handle.
- *
- * @template T
- * @param {ERef<LatestTopic<T>>} topic
- */
-async function* subscribeLatestSimple(topic) {
-  let lastUpdate;
-  await null; // for jessie
-  while (true) {
-    const updateRecord =
-      // eslint-disable-next-line no-await-in-loop
-      await E(topic).getUpdateSince(lastUpdate);
-    lastUpdate = updateRecord.updateCount;
-    yield updateRecord.value;
-  }
-}
-
 /**
  * @file Smart wallet module
  *
@@ -284,6 +268,58 @@ export const prepareSmartWallet = (baggage, shared) => {
 
   const makeOfferWatcher = makeOfferWatcherMaker(baggage);
 
+  const NotifierShape = M.remotable();
+  const updateShape = {
+    value: AmountShape,
+    updateCount: M.bigint(),
+  };
+  const amountWatcherGuard = M.interface('paymentWatcher', {
+    onFulfilled: M.call(updateShape, NotifierShape).returns(),
+    onRejected: M.call(M.any(), NotifierShape).returns(M.promise()),
+  });
+  const prepareAmountWatcher = () =>
+    prepareExoClass(
+      baggage,
+      'AmountWatcher',
+      amountWatcherGuard,
+      /**
+       * @param {Purse} purse
+       * @param {ReturnType<makeWalletWithResolvedStorageNodes>['helper']} helper
+       * @param {string} address
+       */
+      (purse, helper, address) => ({ purse, helper, address }),
+      {
+        /**
+         * @param {{ value: Amount, updateCount: number }} updateRecord
+         * @param { Notifier<Amount> } notifier
+         * @returns {void}
+         */
+        onFulfilled(updateRecord, notifier) {
+          const { helper, purse } = this.state;
+          helper.updateBalance(purse, updateRecord.value);
+          helper.watchNextBalance(
+            this.self,
+            notifier,
+            updateRecord.updateCount,
+          );
+        },
+        /**
+         * @param {unknown} err
+         * @returns {Promise<void>}
+         */
+        onRejected(err) {
+          const { helper, purse, address } = this.state;
+          if (isUpgradeDisconnection(err)) {
+            return helper.watchPurse(purse); // retry
+          }
+          console.error(`*** ${address} failed amount observer, ${err} ***`);
+          throw err;
+        },
+      },
+    );
+
+  const makeAmountWatcher = prepareAmountWatcher();
+
   /**
    * @param {UniqueParams} unique
    * @returns {State}
@@ -369,6 +405,7 @@ export const prepareSmartWallet = (baggage, shared) => {
         .returns(M.promise()),
       publishCurrentState: M.call().returns(),
       watchPurse: M.call(M.eref(PurseShape)).returns(M.promise()),
+      watchNextBalance: M.call(M.any(), NotifierShape, M.bigint()).returns(),
       repairUnwatchedSeats: M.call().returns(),
       updateStatus: M.call(M.any(), M.string()).returns(),
       addContinuingOffer: M.call(
@@ -491,21 +528,18 @@ export const prepareSmartWallet = (baggage, shared) => {
           const purse = await purseRef; // promises don't fit in durable storage
 
           // This would seem to fit the observeNotifier() pattern,
-          // but purse notifiers are not (always) durable.
+          // but purse notifiers are not necessarily durable.
           // If there is an error due to upgrade, retry watchPurse().
-          const notifier = E(purse).getCurrentAmountNotifier();
-          try {
-            // eslint-disable-next-line no-await-in-loop
-            for await (const newBalance of subscribeLatestSimple(notifier)) {
-              helper.updateBalance(purse, newBalance);
-            }
-          } catch (err) {
-            if (isUpgradeDisconnection(err)) {
-              return helper.watchPurse(purse); // retry
-            }
-            console.error(`*** ${address} failed amount observer, ${err} ***`);
-            throw err;
-          }
+          const notifier = await E(purse).getCurrentAmountNotifier();
+
+          const handler = makeAmountWatcher(purse, helper, address);
+          const startP = E(notifier).getUpdateSince(undefined);
+          watchPromise(startP, handler, notifier);
+        },
+
+        watchNextBalance(handler, notifier, updateCount) {
+          const nextP = E(notifier).getUpdateSince(updateCount);
+          watchPromise(nextP, handler, notifier);
         },
 
         /**