make userSeat.getPayout(foo) throw if foo is not present

packages/zoe/src/zoeService/originalZoeSeat.js

@@ -4,14 +4,15 @@ import { E } from '@endo/eventual-send';
 import { M, prepareExoClassKit } from '@agoric/vat-data';
 import { deeplyFulfilled } from '@endo/marshal';
 import { makePromiseKit } from '@endo/promise-kit';
+import { NonNullish } from '@agoric/internal';
 
 import { satisfiesWant } from '../contractFacet/offerSafety.js';
 import '../types-ambient.js';
 import '../internal-types.js';
 import {
   AmountKeywordRecordShape,
-  KeywordShape,
   ExitObjectShape,
+  KeywordShape,
   PaymentPKeywordRecordShape,
 } from '../typeGuards.js';
 
@@ -289,8 +290,10 @@ export const declareOldZoeSeatAdminKind = (baggage, makeDurablePublishKit) => {
           // doExit(), which ensures that finalPayouts() has set state.payouts.
           return E.when(
             state.subscriber.subscribeAfter(),
-            () => state.payouts[keyword],
-            () => state.payouts[keyword],
+            () =>
+              NonNullish(state.payouts[keyword], `No payout for "${keyword}"`),
+            () =>
+              NonNullish(state.payouts[keyword], `No payout for "${keyword}"`),
           );
         },
 

packages/zoe/src/zoeService/types-ambient.js

@@ -199,7 +199,9 @@
  * this seat. The promise will resolve after the seat has exited.
  * @property {(keyword: Keyword) => Promise<Payment<any>>} getPayout
  * returns a promise for the Payment corresponding to the indicated keyword.
- * The promise will resolve after the seat has exited.
+ * The promise will resolve after the seat has exited. If there is no payment
+ * corresponding to the keyword, an error will be thrown. (It used to return
+ * undefined.)
  * @property {() => Promise<OR>} getOfferResult
  * @property {() => void} [tryExit]
  * Note: Only works if the seat's `proposal` has an `OnDemand` `exit` clause. Zoe's

packages/zoe/src/zoeService/zoeSeat.js

@@ -4,6 +4,7 @@ import { E } from '@endo/eventual-send';
 import { M, prepareExoClassKit } from '@agoric/vat-data';
 import { deeplyFulfilled } from '@endo/marshal';
 import { makePromiseKit } from '@endo/promise-kit';
+import { NonNullish } from '@agoric/internal';
 
 import { satisfiesWant } from '../contractFacet/offerSafety.js';
 import '../types-ambient.js';
@@ -143,8 +144,10 @@ export const makeZoeSeatAdminFactory = baggage => {
           // doExit(), which ensures that finalPayouts() has set state.payouts.
           return E.when(
             state.subscriber.subscribeAfter(),
-            () => state.payouts[keyword],
-            () => state.payouts[keyword],
+            () =>
+              NonNullish(state.payouts[keyword], `No payout for "${keyword}"`),
+            () =>
+              NonNullish(state.payouts[keyword], `No payout for "${keyword}"`),
           );
         },
 

packages/zoe/test/unitTests/zcf/zcf.test.js

@@ -973,6 +973,10 @@ test(`userSeat.getPayouts, getPayout from zcf.makeEmptySeatKit`, async t => {
   const payoutAP = E(userSeat).getPayout('A');
   const payoutBP = E(userSeat).getPayout('B');
 
+  await t.throwsAsync(() => E(userSeat).getPayout('C'), {
+    message: /No payout for "C"/,
+  });
+
   t.deepEqual(await payoutPs.A, await payoutAP);
   t.deepEqual(await payoutPs.B, await payoutBP);