feat(vat-data): virtual exos are revocable

packages/swingset-liveslots/src/cache.js

@@ -17,7 +17,7 @@ import { Fail } from '@agoric/assert';
 /**
  * @callback CacheDelete
  * @param {string} key
- * @returns {void}
+ * @returns {boolean}
  *
  * @callback CacheFlush
  * @returns {void}
@@ -82,8 +82,9 @@ export function makeCache(readBacking, writeBacking, deleteBacking) {
     },
     delete: key => {
       assert.typeof(key, 'string');
-      stash.delete(key);
+      const result = stash.delete(key);
       dirtyKeys.add(key);
+      return result;
     },
     flush: () => {
       const keys = [...dirtyKeys.keys()];

packages/swingset-liveslots/src/vatDataTypes.d.ts

@@ -15,6 +15,15 @@ import type {
   WeakSetStore,
 } from '@agoric/store';
 
+import type {
+  FarClassOptions,
+  StateShape,
+  Context,
+  KitContext,
+  Revoker,
+  ReceiveRevoker,
+} from '@endo/exo';
+
 export type { MapStore, Pattern };
 
 // This needs `any` values.  If they were `unknown`, code that uses Baggage
@@ -81,7 +90,12 @@ export type DefineKindOptions<C> = {
    * If provided, it describes the shape of all state records of instances
    * of this kind.
    */
-  stateShape?: { [name: string]: Pattern };
+  stateShape?: StateShape;
+
+  /**
+   * If provided, it is called with a revoke function as an argument.
+   */
+  receiveRevoker?: ReceiveRevoker;
 
   /**
    * Intended for internal use only.

packages/swingset-liveslots/src/virtualObjectManager.js

@@ -153,6 +153,9 @@ const makeContextCache = (makeState, makeContext) => {
 const makeContextProvider = (contextCache, getSlotForVal) =>
   harden(rep => contextCache.get(getSlotForVal(rep)));
 
+const makeContextRevoker = (contextCache, getSlotForVal) =>
+  harden(rep => contextCache.delete(getSlotForVal(rep)));
+
 const makeContextProviderKit = (contextCache, getSlotForVal, facetNames) => {
   /** @type { Record<string, any> } */
   const contextProviderKit = {};
@@ -174,6 +177,13 @@ const makeContextProviderKit = (contextCache, getSlotForVal, facetNames) => {
   return harden(contextProviderKit);
 };
 
+// TODO BUG The returned function revokes the whole kit, i.e., all vrefs
+// sharing the same baseRef. This makes me wonder whether I need to rethink
+// revocation yet again. Perhaps an entire kit is the correct unit and
+// the api should be reconcieved.
+const makeContextFacetRevoker = (contextCache, getSlotForVal) =>
+  harden(rep => contextCache.delete(parseVatSlot(getSlotForVal(rep)).baseRef));
+
 // The management of single Representatives (i.e. defineKind) is very similar
 // to that of a cohort of facets (i.e. defineKindMulti). In this description,
 // we use "self/facets" to refer to either 'self' or 'facets', as appropriate
@@ -719,6 +729,7 @@ export const makeVirtualObjectManager = (
       stateShape = undefined,
       thisfulMethods = false,
       interfaceGuard = undefined,
+      receiveRevoker = undefined,
     } = options;
 
     const statePrototype = {}; // Not frozen yet
@@ -1043,6 +1054,13 @@ export const makeVirtualObjectManager = (
       return val;
     };
 
+    if (receiveRevoker) {
+      const makeRevoker = multifaceted
+        ? makeContextFacetRevoker
+        : makeContextRevoker;
+      receiveRevoker(makeRevoker(contextCache, getSlotForVal));
+    }
+
     return makeNewInstance;
   };
 

packages/vat-data/test/test-revoke-virtual.js

@@ -0,0 +1,131 @@
+// Modeled on test-revoke-heap-classes.js
+
+import { test } from './prepare-test-env-ava.js';
+
+// eslint-disable-next-line import/order
+import { M } from '@agoric/store';
+import {
+  defineVirtualExoClass,
+  defineVirtualExoClassKit,
+} from '../src/exo-utils.js';
+
+const { apply } = Reflect;
+
+const UpCounterI = M.interface('UpCounter', {
+  incr: M.call()
+    // TODO M.number() should not be needed to get a better error message
+    .optional(M.and(M.number(), M.gte(0)))
+    .returns(M.number()),
+});
+
+const DownCounterI = M.interface('DownCounter', {
+  decr: M.call()
+    // TODO M.number() should not be needed to get a better error message
+    .optional(M.and(M.number(), M.gte(0)))
+    .returns(M.number()),
+});
+
+test('test revoke defineVirtualExoClass', t => {
+  let revoke;
+  const makeUpCounter = defineVirtualExoClass(
+    'UpCounter',
+    UpCounterI,
+    /** @param {number} x */
+    (x = 0) => ({ x }),
+    {
+      incr(y = 1) {
+        const { state } = this;
+        state.x += y;
+        return state.x;
+      },
+    },
+    {
+      receiveRevoker(r) {
+        revoke = r;
+      },
+    },
+  );
+  const upCounter = makeUpCounter(3);
+  t.is(upCounter.incr(5), 8);
+  // @ts-expect-error Does not understand that `revoke` is a function.
+  t.is(revoke(upCounter), true);
+  t.throws(() => upCounter.incr(1), {
+    message:
+      '"In \\"incr\\" method of (UpCounter)" may only be applied to a valid instance: "[Alleged: UpCounter]"',
+  });
+});
+
+test('test revoke defineVirtualExoClassKit', t => {
+  let revoke;
+  const makeCounterKit = defineVirtualExoClassKit(
+    'Counter',
+    { up: UpCounterI, down: DownCounterI },
+    /** @param {number} x */
+    (x = 0) => ({ x }),
+    {
+      up: {
+        incr(y = 1) {
+          const { state } = this;
+          state.x += y;
+          return state.x;
+        },
+      },
+      down: {
+        decr(y = 1) {
+          const { state } = this;
+          state.x -= y;
+          return state.x;
+        },
+      },
+    },
+    {
+      receiveRevoker(r) {
+        revoke = r;
+      },
+    },
+  );
+  const { up: upCounter, down: downCounter } = makeCounterKit(3);
+  t.is(upCounter.incr(5), 8);
+  t.is(downCounter.decr(), 7);
+  // @ts-expect-error Does not understand that `revoke` is a function.
+  t.is(revoke(upCounter), true);
+  t.throws(() => upCounter.incr(3), {
+    message:
+      '"In \\"incr\\" method of (Counter up)" may only be applied to a valid instance: "[Alleged: Counter up]"',
+  });
+  // @ts-expect-error Does not understand that `revoke` is a function.
+  t.is(revoke(downCounter), false);
+  t.throws(() => downCounter.decr(), {
+    message:
+      '"In \\"decr\\" method of (Counter down)" may only be applied to a valid instance: "[Alleged: Counter down]"',
+  });
+});
+
+test('test virtual facet cross-talk', t => {
+  const makeCounterKit = defineVirtualExoClassKit(
+    'Counter',
+    { up: UpCounterI, down: DownCounterI },
+    /** @param {number} x */
+    (x = 0) => ({ x }),
+    {
+      up: {
+        incr(y = 1) {
+          const { state } = this;
+          state.x += y;
+          return state.x;
+        },
+      },
+      down: {
+        decr(y = 1) {
+          const { state } = this;
+          state.x -= y;
+          return state.x;
+        },
+      },
+    },
+  );
+  const { up: upCounter, down: downCounter } = makeCounterKit(3);
+  t.throws(() => apply(upCounter.incr, downCounter, [2]), {
+    message: 'illegal cross-facet access',
+  });
+});