Don't use process when not available

packages/firestore/src/local/indexeddb_mutation_queue.ts

@@ -47,7 +47,7 @@ import { LocalSerializer } from './local_serializer';
 import { MutationQueue } from './mutation_queue';
 import { PersistenceTransaction, ReferenceDelegate } from './persistence';
 import { PersistencePromise } from './persistence_promise';
-import { SimpleDbStore, SimpleDbTransaction } from './simple_db';
+import { SimpleDb, SimpleDbStore, SimpleDbTransaction } from './simple_db';
 
 /** A mutation queue for a specific user, backed by IndexedDB. */
 export class IndexedDbMutationQueue implements MutationQueue {
@@ -675,7 +675,7 @@ function convertStreamToken(token: ProtoByteString): string {
   if (token instanceof Uint8Array) {
     // TODO(b/78771403): Convert tokens to strings during deserialization
     assert(
-      process.env.USE_MOCK_PERSISTENCE === 'YES',
+      SimpleDb.isMockPersistence(),
       'Persisting non-string stream tokens is only supported with mock persistence.'
     );
     return token.toString();

packages/firestore/src/local/local_serializer.ts

@@ -43,6 +43,7 @@ import {
   DbUnknownDocument
 } from './indexeddb_schema';
 import { QueryData, QueryPurpose } from './query_data';
+import { SimpleDb } from './simple_db';
 
 /** Serializer for values stored in the LocalStore. */
 export class LocalSerializer {
@@ -251,7 +252,7 @@ export class LocalSerializer {
     if (queryData.resumeToken instanceof Uint8Array) {
       // TODO(b/78771403): Convert tokens to strings during deserialization
       assert(
-        process.env.USE_MOCK_PERSISTENCE === 'YES',
+        SimpleDb.isMockPersistence(),
         'Persisting non-string stream tokens is only supported with mock persistence .'
       );
       resumeToken = queryData.resumeToken.toString();

packages/firestore/src/local/simple_db.ts

@@ -149,20 +149,25 @@ export class SimpleDb {
     if (typeof window === 'undefined' || window.indexedDB == null) {
       return false;
     }
+
+    if (SimpleDb.isMockPersistence()) {
+      return true;
+    }
+
+    // In some Node environments, `window` is defined, but `window.navigator` is
+    // not. We don't support IndexedDB persistence in Node if the
+    // isMockPersistence() check above returns false.
+    if (window.navigator === undefined) {
+      return false;
+    }
+
     // We extensively use indexed array values and compound keys,
     // which IE and Edge do not support. However, they still have indexedDB
     // defined on the window, so we need to check for them here and make sure
     // to return that persistence is not enabled for those browsers.
     // For tracking support of this feature, see here:
     // https://developer.microsoft.com/en-us/microsoft-edge/platform/status/indexeddbarraysandmultientrysupport/
 
-    // If we are running in Node using the IndexedDBShim, `window` is defined,
-    // but `window.navigator` is not. In this case, we support IndexedDB and
-    // return `true`.
-    if (window.navigator === undefined) {
-      return process.env.USE_MOCK_PERSISTENCE === 'YES';
-    }
-
     // Check the UA string to find out the browser.
     const ua = getUA();
 
@@ -197,6 +202,17 @@ export class SimpleDb {
     }
   }
 
+  /**
+   * Returns true if the backing IndexedDB store is the Node IndexedDBShim
+   * (see https://github.com/axemclion/IndexedDBShim).
+   */
+  static isMockPersistence(): boolean {
+    return (
+      typeof process !== 'undefined' &&
+      process.env.USE_MOCK_PERSISTENCE === 'YES'
+    );
+  }
+
   /** Helper to get a typed SimpleDbStore from a transaction. */
   static getStore<KeyType extends IDBValidKey, ValueType extends unknown>(
     txn: SimpleDbTransaction,