switch to isolating change within LocalStorage processor

src/main-thread/commands/storage.ts

@@ -64,8 +64,8 @@ export const StorageProcessor: CommandExecutorInterface = (strings, nodeContext,
 
         // TODO(choumx): Clean up key/value strings (or don't store them in the first place)
         // to avoid leaking memory.
-        const key = keyIndex > 0 ? strings.get(keyIndex) : '';
-        const value = valueIndex > 0 ? strings.get(valueIndex) : null;
+        const key = keyIndex > 0 ? strings.get(keyIndex - 1) : '';
+        const value = valueIndex > 0 ? strings.get(valueIndex - 1) : null;
 
         if (operation === GetOrSet.GET) {
           get(location, key);
@@ -82,8 +82,8 @@ export const StorageProcessor: CommandExecutorInterface = (strings, nodeContext,
       const keyIndex = mutations[startPosition + StorageMutationIndex.Key];
       const valueIndex = mutations[startPosition + StorageMutationIndex.Value];
 
-      const key = keyIndex > 0 ? strings.get(keyIndex) : null;
-      const value = valueIndex > 0 ? strings.get(valueIndex) : null;
+      const key = keyIndex > 0 ? strings.get(keyIndex - 1) : null;
+      const value = valueIndex > 0 ? strings.get(valueIndex - 1) : null;
 
       return {
         type: 'STORAGE',

src/main-thread/strings.ts

@@ -5,11 +5,7 @@ export class StringContext {
   private strings: Array<string>;
 
   constructor() {
-    this.strings = [
-      // The 0th index is reserved for meaning no value. Or delete.
-      // For example, the storage.removeItem code path.
-      null as any,
-    ];
+    this.strings = [];
   }
 
   /**
@@ -27,6 +23,8 @@ export class StringContext {
 
   /**
    * Stores a string in mapping and returns the index of the location.
+   * @param value string to store
+   * @return {number}
    */
   store(value: string): number {
     this.strings.push(value);

src/test/Emitter.ts

@@ -15,10 +15,7 @@ export interface Emitter {
  * mutation transfer state is also stored at the module-level.
  * TODO: Remove this and replace with strings.getForTesting() at call sites.
  */
-const strings: Array<string> = [
-  // First index reserved to signify deletion.
-  null as any,
-];
+const strings: Array<string> = [];
 
 /**
  * Stubs `document.postMessage` to invoke callbacks passed to `once()`.

src/test/main-thread/commands/function.test.ts

@@ -29,7 +29,7 @@ test('Returns the value of a resolved function', async (t) => {
   const mutations: number[] = [];
   mutations[FunctionMutationIndex.Status] = ResolveOrReject.RESOLVE;
   mutations[FunctionMutationIndex.Index] = index;
-  mutations[FunctionMutationIndex.Value] = 1;
+  mutations[FunctionMutationIndex.Value] = 0;
 
   processor.execute(new Uint16Array(mutations), 0, true);
   t.deepEqual(await promise, { val: true });
@@ -41,7 +41,7 @@ test('Is able to return undefined', async (t) => {
   const mutations: number[] = [];
   mutations[FunctionMutationIndex.Status] = ResolveOrReject.RESOLVE;
   mutations[FunctionMutationIndex.Index] = index;
-  mutations[FunctionMutationIndex.Value] = 1;
+  mutations[FunctionMutationIndex.Value] = 0;
 
   processor.execute(new Uint16Array(mutations), 0, true);
   t.deepEqual(await promise, undefined);
@@ -53,7 +53,7 @@ test('Returns the value of a rejected value', (t) => {
   const mutations: number[] = [];
   mutations[FunctionMutationIndex.Status] = ResolveOrReject.REJECT;
   mutations[FunctionMutationIndex.Index] = index;
-  mutations[FunctionMutationIndex.Value] = 1;
+  mutations[FunctionMutationIndex.Value] = 0;
 
   processor.execute(new Uint16Array(mutations), 0, true);
   return promise.then(

src/test/main-thread/mutator.test.ts

@@ -70,9 +70,9 @@ test.serial('batch mutations', (t) => {
     new Uint16Array([
       TransferrableMutationType.ATTRIBUTES,
       2, // Base Node
-      1,
       0,
-      1 + 1,
+      0,
+      0 + 1,
     ]),
   );
   mutator.mutate(
@@ -82,9 +82,9 @@ test.serial('batch mutations', (t) => {
     new Uint16Array([
       TransferrableMutationType.ATTRIBUTES,
       2, // Base Node
-      2,
+      1,
       0,
-      2 + 1,
+      1 + 1,
     ]),
   );
 
@@ -102,9 +102,9 @@ test.serial('batch mutations', (t) => {
     new Uint16Array([
       TransferrableMutationType.ATTRIBUTES,
       2, // Base Node
-      3,
+      2,
       0,
-      3 + 1,
+      2 + 1,
     ]),
   );
 
@@ -140,9 +140,9 @@ test.serial('batch mutations with custom pump', (t) => {
     new Uint16Array([
       TransferrableMutationType.ATTRIBUTES,
       2, // Base Node
-      1,
       0,
-      1 + 1,
+      0,
+      0 + 1,
     ]),
   );
   mutator.mutate(
@@ -152,9 +152,9 @@ test.serial('batch mutations with custom pump', (t) => {
     new Uint16Array([
       TransferrableMutationType.ATTRIBUTES,
       2, // Base Node
-      2,
+      1,
       0,
-      2 + 1,
+      1 + 1,
     ]),
   );
 
@@ -174,9 +174,9 @@ test.serial('batch mutations with custom pump', (t) => {
     new Uint16Array([
       TransferrableMutationType.ATTRIBUTES,
       2, // Base Node
-      3,
+      2,
       0,
-      3 + 1,
+      2 + 1,
     ]),
   );
 
@@ -209,9 +209,9 @@ test.serial('leverage allowlist to exclude mutation type', (t) => {
     new Uint16Array([
       TransferrableMutationType.ATTRIBUTES,
       2, // Base Node
-      1,
       0,
-      1 + 1,
+      0,
+      0 + 1,
     ]),
   );
   mutator.mutate(
@@ -221,9 +221,9 @@ test.serial('leverage allowlist to exclude mutation type', (t) => {
     new Uint16Array([
       TransferrableMutationType.ATTRIBUTES,
       2, // Base Node
-      2,
+      1,
       0,
-      2 + 1,
+      1 + 1,
     ]),
   );
 
@@ -257,9 +257,9 @@ test.serial('split strings from mutations', (t) => {
     new Uint16Array([
       TransferrableMutationType.ATTRIBUTES,
       2, // Base Node
-      1,
       0,
-      1 + 1,
+      0,
+      0 + 1,
     ]),
   );
 

src/test/mutation-transfer/storage.test.ts

@@ -54,7 +54,7 @@ test.serial.cb('Storage.removeItem', (t) => {
   const { document, storage } = t.context;
 
   expectMutations(document, (mutations) => {
-    t.deepEqual(mutations, [TransferrableMutationType.STORAGE, GetOrSet.SET, StorageLocation.Local, getForTesting('foo'), 0]);
+    t.deepEqual(mutations, [TransferrableMutationType.STORAGE, GetOrSet.SET, StorageLocation.Local, getForTesting('foo')! + 1, 0]);
     t.end();
   });
 

src/worker-thread/Storage.ts

@@ -62,7 +62,7 @@ export function createStorage(document: Document | DocumentStub, location: Stora
         TransferrableMutationType.STORAGE,
         GetOrSet.SET,
         location,
-        store(key),
+        store(key) + 1,
         0, // value == 0 represents deletion.
       ]);
     },

src/worker-thread/strings.ts

@@ -1,4 +1,4 @@
-let count: number = 1; // count starts from 1 since 0th index is reserved to mean "no value" or "delete".
+let count: number = 0;
 let transfer: Array<string> = [];
 const mapping: Map<string, number> = new Map();