fix(purse): amountShape param

packages/ERTP/src/typeGuards.js

@@ -77,6 +77,12 @@ export const AmountShape = harden({
   value: AmountValueShape,
 });
 
+/** For parameters that are themselves an AmountShape pattern. */
+export const AmountShapeShape = harden({
+  brand: M.pattern(),
+  value: M.pattern(),
+});
+
 export const RatioShape = harden({
   numerator: AmountShape,
   denominator: AmountShape,

packages/ERTP/test/unitTests/typeGuards.test.js

@@ -0,0 +1,18 @@
+import test from 'ava';
+
+import { M, matches } from '@endo/patterns';
+import { Far } from '@endo/far';
+import { AmountShape, AmountShapeShape } from '../../src/typeGuards.js';
+
+test('AmountShape', t => {
+  t.truthy(matches(harden({ brand: Far('brand'), value: 123n }), AmountShape));
+});
+
+test('AmountShapeShape', t => {
+  t.truthy(
+    matches(
+      harden({ brand: M.remotable('brand'), value: M.nat() }),
+      AmountShapeShape,
+    ),
+  );
+});

packages/vats/src/virtual-purse.js

@@ -4,6 +4,7 @@ import { isPromise } from '@endo/promise-kit';
 
 import {
   AmountShape,
+  AmountShapeShape,
   BrandShape,
   DepositFacetShape,
   NotifierShape,
@@ -37,7 +38,7 @@ export const makeVirtualPurseKitIKit = (
     // to this raw method to validate that this remotable is actually
     // a live payment of the correct brand with sufficient funds.
     deposit: M.callWhen(PaymentShape)
-      .optional(M.pattern())
+      .optional(AmountShapeShape)
       .returns(amountShape),
     getDepositFacet: M.callWhen().returns(DepositFacetShape),
     withdraw: M.callWhen(amountShape).returns(PaymentShape),
@@ -50,7 +51,9 @@ export const makeVirtualPurseKitIKit = (
   });
 
   const RetainRedeemI = M.interface('RetainRedeem', {
-    retain: M.callWhen(PaymentShape).optional(amountShape).returns(amountShape),
+    retain: M.callWhen(PaymentShape)
+      .optional(AmountShapeShape)
+      .returns(amountShape),
     redeem: M.callWhen(amountShape).returns(PaymentShape),
   });