refactor: Move DisconnectionObject generation/testing into "internal"

packages/SwingSet/src/kernel/kernel.js

@@ -1,6 +1,7 @@
 import { assert, Fail } from '@agoric/assert';
 import { isNat } from '@endo/nat';
 import { importBundle } from '@endo/import-bundle';
+import { makeUpgradeDisconnection } from '@agoric/internal/src/upgrade-api.js';
 import { assertKnownOptions } from '../lib/assertOptions.js';
 import { foreverPolicy } from '../lib/runPolicies.js';
 import { kser, kslot, makeError } from '../lib/kmarshal.js';
@@ -825,12 +826,11 @@ export default function buildKernel(
     const { meterID } = vatInfo;
     let computrons;
     const vatKeeper = kernelKeeper.provideVatKeeper(vatID);
-    const disconnectObject = {
-      name: 'vatUpgraded',
+    const disconnectionObject = makeUpgradeDisconnection(
       upgradeMessage,
-      incarnationNumber: vatKeeper.getIncarnationNumber(),
-    };
-    const disconnectionCapData = kser(disconnectObject);
+      vatKeeper.getIncarnationNumber(),
+    );
+    const disconnectionCapData = kser(disconnectionObject);
 
     /**
      * Terminate the vat and translate internal-delivery results into

packages/SwingSet/src/types-external.js

@@ -65,7 +65,7 @@ export {};
  * @typedef { import('@agoric/swingset-liveslots').Message } Message
  *
  * @typedef { 'none' | 'ignore' | 'logAlways' | 'logFailure' | 'panic' } ResolutionPolicy
- * @typedef {{ name: string, upgradeMessage: string, incarnationNumber: number }} DisconnectObject
+ * @typedef {import('@agoric/internal/src/upgrade-api.js').DisconnectionObject} DisconnectionObject
  *
  * @typedef { import('@agoric/swingset-liveslots').VatDeliveryObject } VatDeliveryObject
  * @typedef { import('@agoric/swingset-liveslots').VatOneResolution } VatOneResolution

packages/internal/src/upgrade-api.js

@@ -0,0 +1,41 @@
+// @ts-check
+// @jessie-check
+import { isObject } from '@endo/marshal';
+
+/**
+ * @typedef {{ name: string, upgradeMessage: string, incarnationNumber: number }} DisconnectionObject
+ */
+
+/**
+ * Makes an Error-like object for use as the rejection value of promises
+ * abandoned by upgrade.
+ *
+ * @param {string} upgradeMessage
+ * @param {number} toIncarnationNumber
+ * @returns {DisconnectionObject}
+ */
+export const makeUpgradeDisconnection = (upgradeMessage, toIncarnationNumber) =>
+  harden({
+    name: 'vatUpgraded',
+    upgradeMessage,
+    incarnationNumber: toIncarnationNumber,
+  });
+harden(makeUpgradeDisconnection);
+
+// TODO: Simplify once we have @endo/patterns (or just export the shape).
+// const upgradeDisconnectionShape = harden({
+//   name: 'vatUpgraded',
+//   upgradeMessage: M.string(),
+//   incarnationNumber: M.number(),
+// });
+// const isUpgradeDisconnection = err => matches(err, upgradeDisconnectionShape);
+/**
+ * @param {any} err
+ * @returns {err is DisconnectionObject}
+ */
+export const isUpgradeDisconnection = err =>
+  isObject(err) &&
+  err.name === 'vatUpgraded' &&
+  typeof err.upgradeMessage === 'string' &&
+  typeof err.incarnationNumber === 'number';
+harden(isUpgradeDisconnection);

packages/internal/test/test-upgrade-api.js

@@ -0,0 +1,21 @@
+// @ts-check
+import '@endo/init';
+import test from 'ava';
+import {
+  makeUpgradeDisconnection,
+  isUpgradeDisconnection,
+} from '../src/upgrade-api.js';
+
+test('isUpgradeDisconnection must recognize disconnection objects', t => {
+  const disconnection = makeUpgradeDisconnection('vat upgraded', 2);
+  t.true(isUpgradeDisconnection(disconnection));
+});
+
+test('isUpgradeDisconnection must recognize original-format disconnection objects', t => {
+  const disconnection = harden({
+    name: 'vatUpgraded',
+    upgradeMessage: 'vat upgraded',
+    incarnationNumber: 2,
+  });
+  t.true(isUpgradeDisconnection(disconnection));
+});

packages/notifier/src/subscribe.js

@@ -1,6 +1,5 @@
 import { E, Far } from '@endo/far';
-import { isObject } from '@endo/marshal';
-import { isNat } from '@endo/nat';
+import { isUpgradeDisconnection } from '@agoric/internal/src/upgrade-api.js';
 
 import './types-ambient.js';
 
@@ -15,7 +14,7 @@ const sink = () => {};
  * @returns {Promise<T>}
  */
 const reconnectAsNeeded = async thunk => {
-  let lastVersion;
+  let lastVersion = -Infinity;
   // End synchronous prelude.
   await null;
   for (;;) {
@@ -24,13 +23,9 @@ const reconnectAsNeeded = async thunk => {
       const result = await thunk();
       return result;
     } catch (err) {
-      /** @see processUpgrade in {@link ../../SwingSet/src/kernel/kernel.js} */
-      if (isObject(err) && err.name === 'vatUpgraded') {
+      if (isUpgradeDisconnection(err)) {
         const { incarnationNumber: version } = err;
-        if (
-          isNat(version) &&
-          (lastVersion === undefined || version > lastVersion)
-        ) {
+        if (version > lastVersion) {
           // We don't expect another upgrade in between receiving
           // a disconnection and re-requesting an update, but must
           // nevertheless be prepared for that.