addressing review comments

Author: tanderson-ld

packages/shared/sdk-server/src/api/subsystems/LDDataSourceUpdates.ts

@@ -48,7 +48,7 @@ export interface LDDataSourceUpdates {
    * @param data An object in which each key is the "namespace" of a collection (e.g. `"features"`) and
    * the value is an object that maps keys to entities. The actual type of this parameter is
    * `interfaces.FullDataSet<VersionedData>`.
-   * @param selector TODO
+   * @param selector opaque string that uniquely identifies the state that contains the changes
    * @param callback Will be called after the changes are applied.
    */
   applyChanges(

packages/shared/sdk-server/src/api/subsystems/LDFeatureStore.ts

@@ -138,13 +138,16 @@ export interface LDFeatureStore {
   upsert(kind: DataKind, data: LDKeyedFeatureStoreItem, callback: () => void): void;
 
   /**
+   * Applies the provided data onto the existing data, replacing all data or upserting depending
+   * on the basis parameter.
+   *
    * @param basis If true, completely overwrites the current contents of the data store
    * with the provided data.  If false, upserts the items in the provided data.  Upserts
    * are made only if provided items have newer versions than existing items.
    * @param data An object in which each key is the "namespace" of a collection (e.g. `"features"`) and
    * the value is an object that maps keys to entities. The actual type of this parameter is
    * `interfaces.FullDataSet<VersionedData>`.
-   * @param selector TODO
+   * @param selector opaque string that uniquely identifies the state that contains the changes
    * @param callback Will be called after the changes are applied.
    */
   applyChanges(

packages/shared/sdk-server/src/store/InMemoryFeatureStore.ts

@@ -70,19 +70,25 @@ export default class InMemoryFeatureStore implements LDFeatureStore {
   applyChanges(
     basis: boolean,
     data: LDFeatureStoreDataStorage,
-    selector: String | undefined, // TODO handle selector
+    selector: String | undefined, // TODO: SDK-1044 - Utilize selector
     callback: () => void,
   ): void {
     if (basis) {
       this._initCalled = true;
       this._allData = data;
     } else {
+      const tempData: LDFeatureStoreDataStorage = {};
+      // shallow copy to protect against concurrent read
+      Object.entries(this._allData).forEach(([namespace, items]) => {
+        tempData[namespace] = { ...items };
+      });
+
       Object.entries(data).forEach(([namespace, items]) => {
         Object.keys(items || {}).forEach((key) => {
-          let existingItems = this._allData[namespace];
+          let existingItems = tempData[namespace];
           if (!existingItems) {
             existingItems = {};
-            this._allData[namespace] = existingItems;
+            tempData[namespace] = existingItems;
           }
           const item = items[key];
           if (Object.hasOwnProperty.call(existingItems, key)) {
@@ -95,6 +101,8 @@ export default class InMemoryFeatureStore implements LDFeatureStore {
           }
         });
       });
+
+      this._allData = tempData;
     }
 
     callback?.();