Bug 1458640 - Prevent any fatal indexedDB errors from crashing section

system-addon/lib/ASRouter.jsm

@@ -91,7 +91,7 @@ class _ASRouter {
     this.initialized = true;
     this._storage = storage;
 
-    const blockList = await this._storage.get("blockList");
+    const blockList = await this._storage.get("blockList") || [];
     this.setState({blockList});
   }
 

system-addon/lib/ActivityStreamStorage.jsm

@@ -16,7 +16,7 @@ this.ActivityStreamStorage = class ActivityStreamStorage {
   }
 
   get db() {
-    return this._db || (this._db = this._openDatabase());
+    return this._db || (this._db = this.createOrOpenDb());
   }
 
   /**
@@ -65,6 +65,26 @@ this.ActivityStreamStorage = class ActivityStreamStorage {
     });
   }
 
+  /**
+   * createOrOpenDb - Open a db (with this.dbName) if it exists.
+   *                  If it does not exist, create it.
+   *                  If an error occurs, deleted the db and attempt to
+   *                  re-create it.
+   * @returns Promise that resolves with a db instance
+   */
+  async createOrOpenDb() {
+    try {
+      const db = await this._openDatabase();
+      return db;
+    } catch (e) {
+      if (this.telemetry) {
+        this.telemetry.handleUndesiredEvent({data: {event: "INDEXEDDB_OPEN_FAILED"}});
+      }
+      await IndexedDB.deleteDatabase(this.dbName);
+      return this._openDatabase();
+    }
+  }
+
   async _requestWrapper(request) {
     let result = null;
     try {

system-addon/test/unit/lib/ActivityStreamStorage.test.js

@@ -9,7 +9,10 @@ describe("ActivityStreamStorage", () => {
   let storage;
   beforeEach(() => {
     sandbox = sinon.sandbox.create();
-    indexedDB = {open: sandbox.stub().resolves({})};
+    indexedDB = {
+      open: sandbox.stub().resolves({}),
+      deleteDatabase: sandbox.stub().resolves()
+    };
     overrider.set({IndexedDB: indexedDB});
     storage = new ActivityStreamStorage({
       storeNames: ["storage_test"],
@@ -19,12 +22,25 @@ describe("ActivityStreamStorage", () => {
   afterEach(() => {
     sandbox.restore();
   });
-  it("should not throw an error when accessing db", async () => {
-    assert.ok(storage.db);
-  });
   it("should throw if required arguments not provided", () => {
     assert.throws(() => new ActivityStreamStorage({telemetry: true}));
   });
+  describe(".db", () => {
+    it("should not throw an error when accessing db", async () => {
+      assert.ok(storage.db);
+    });
+
+    it("should delete and recreate the db if opening db fails", async () => {
+      const newDb = {};
+      indexedDB.open.onFirstCall().rejects(new Error("fake error"));
+      indexedDB.open.onSecondCall().resolves(newDb);
+
+      const db = await storage.db;
+      assert.calledOnce(indexedDB.deleteDatabase);
+      assert.calledTwice(indexedDB.open);
+      assert.equal(db, newDb);
+    });
+  });
   describe("#getDbTable", () => {
     let testStorage;
     let storeStub;