fix: correct oversights & editing errors in virtual object code

Author: FUDCo

packages/SwingSet/src/kernel/virtualObjectManager.js

@@ -37,7 +37,10 @@ export function makeCache(size, fetch, store) {
           }
         }
         liveTable.delete(lruTail.vobjID);
-        store(lruTail.vobjID, lruTail.rawData);
+        if (lruTail.dirty) {
+          store(lruTail.vobjID, lruTail.rawData);
+          lruTail.dirty = false;
+        }
         lruTail.rawData = null;
         if (lruTail.prev) {
           lruTail.prev.next = undefined;
@@ -115,7 +118,7 @@ export function makeCache(size, fetch, store) {
  * @param {*} m The vat's marshaler.
  * @param {number} cacheSize How many virtual objects this manager should cache
  *   in memory.
- * @returns {*} a new virtual object manager.
+ * @returns {Object} a new virtual object manager.
  *
  * The virtual object manager allows the creation of persistent objects that do
  * not need to occupy memory when they are not in use.  It provides four
@@ -395,6 +398,7 @@ export function makeVirtualObjectManager(
               const serializedValue = m.serialize(value);
               ensureState(innerSelf);
               innerSelf.rawData[prop] = serializedValue;
+              innerSelf.dirty = true;
             },
           });
         }
@@ -437,8 +441,9 @@ export function makeVirtualObjectManager(
       const innerSelf = { vobjID, rawData: initialData };
       const initialRepresentative = makeRepresentative(innerSelf, true);
       const initialize = initialRepresentative.initialize;
+      delete initialRepresentative.initialize;
+      harden(initialRepresentative);
       if (initialize) {
-        delete initialRepresentative.initialize;
         initialize(...args);
       }
       delete initialData[initializationInProgress];
@@ -453,6 +458,7 @@ export function makeVirtualObjectManager(
       }
       innerSelf.rawData = rawData;
       innerSelf.wrapData(initialData);
+      innerSelf.dirty = true;
       return initialRepresentative;
     }
 

packages/SwingSet/test/virtualObjects/test-virtualObjectCache.js

@@ -37,6 +37,7 @@ function makeThing(n) {
   return {
     vobjID: `t${n}`,
     rawData: `thing #${n}`,
+    dirty: true,
   };
 }
 
@@ -71,6 +72,7 @@ test('cache overflow and refresh', t => {
 
   // lookup that has no effect
   things[0] = cache.lookup('t0'); // cache: t0, t2, t5, t4
+  things[0].dirty = true; // pretend we changed it
   t.is(things[0].rawData, 'thing #0');
   t.is(things[3].rawData, null);
   t.deepEqual(store.getLog(), [
@@ -100,7 +102,6 @@ test('cache overflow and refresh', t => {
     ['store', 't2', 'thing #2'],
     ['store', 't0', 'thing #0'],
     ['store', 't4', 'thing #4'],
-    ['store', 't1', 'thing #1'],
   ]);
   t.deepEqual(store.dump(), [
     ['t0', 'thing #0'],
@@ -114,16 +115,22 @@ test('cache overflow and refresh', t => {
   // verify that changes get written
   things[0] = cache.lookup('t0'); // cache: t0
   things[0].rawData = 'new thing #0';
+  things[0].dirty = true;
   things[1] = cache.lookup('t1'); // cache: t1, t0
   things[1].rawData = 'new thing #1';
+  things[1].dirty = true;
   things[2] = cache.lookup('t2'); // cache: t2, t1, t0
   things[2].rawData = 'new thing #2';
+  things[2].dirty = true;
   things[3] = cache.lookup('t3'); // cache: t3, t2, t1, t0
   things[3].rawData = 'new thing #3';
+  things[3].dirty = true;
   things[4] = cache.lookup('t4'); // cache: t4, t3, t2, t1
   things[4].rawData = 'new thing #4';
+  things[4].dirty = true;
   things[5] = cache.lookup('t5'); // cache: t5, t4, t3, t2
   things[5].rawData = 'new thing #5';
+  things[5].dirty = true;
   t.is(things[0].rawData, null);
   t.is(things[5].rawData, 'new thing #5');
   t.deepEqual(store.getLog(), [