Make maybeGarbageCollectMultiClientState idempotent (#2275)

Author: schmidt-sebastian

packages/firestore/CHANGELOG.md

@@ -1,12 +1,16 @@
 # Unreleased
+- [changed] Improved iOS 13 support by eliminating an additional crash in our
+  IndexedDB persistence layer.
+
+# 1.6.2
 - [changed] Fixed a crash on iOS 13 that occurred when persistence was enabled
   in a background tab (#2232).
 - [fixed] Fixed an issue in the interaction with the Firestore Emulator that
   caused requests with timestamps to fail.
+  
+# 1.6.0
 - [feature] Added a `Firestore.onSnapshotsInSync()` method that notifies you
   when all your snapshot listeners are in sync with each other.
-
-# 1.6.0
 - [fixed] Fixed a regression that caused queries with nested field filters to
   crash the client if the field was not present in the local copy of the
   document. 

packages/firestore/src/local/indexeddb_persistence.ts

@@ -451,33 +451,30 @@ export class IndexedDbPersistence implements Persistence {
     ) {
       this.lastGarbageCollectionTime = Date.now();
 
-      let activeClients: DbClientMetadata[];
-      let inactiveClients: DbClientMetadata[] = [];
-
-      await this.runTransaction(
+      const inactiveClients = await this.runTransaction(
         'maybeGarbageCollectMultiClientState',
-        'readwrite-primary',
+        'readwrite-primary-idempotent',
         txn => {
           const metadataStore = IndexedDbPersistence.getStore<
             DbClientMetadataKey,
             DbClientMetadata
           >(txn, DbClientMetadata.store);
 
           return metadataStore.loadAll().next(existingClients => {
-            activeClients = this.filterActiveClients(
+            const active = this.filterActiveClients(
               existingClients,
               MAX_CLIENT_AGE_MS
             );
-            inactiveClients = existingClients.filter(
-              client => activeClients.indexOf(client) === -1
+            const inactive = existingClients.filter(
+              client => active.indexOf(client) === -1
             );
 
             // Delete metadata for clients that are no longer considered active.
             return PersistencePromise.forEach(
-              inactiveClients,
+              inactive,
               (inactiveClient: DbClientMetadata) =>
                 metadataStore.delete(inactiveClient.clientId)
-            );
+            ).next(() => inactive);
           });
         }
       );

packages/firestore/src/local/simple_db.ts

@@ -303,6 +303,7 @@ export class SimpleDb {
           isDomException(e) &&
           attemptNumber < TRANSACTION_RETRY_COUNT;
         debug(
+          LOG_TAG,
           'Transaction failed with error: %s. Retrying: %s.',
           e.message,
           retryable