fix(firestore, apple): issue where setting persistence caused a crash. kFIRFirestoreCacheSizeUnlimited no longer usable.

packages/cloud_firestore/cloud_firestore/example/integration_test/instance_e2e.dart

@@ -260,6 +260,50 @@ void runInstanceTests() {
         await FirebaseFirestore.setLoggingEnabled(true);
         await FirebaseFirestore.setLoggingEnabled(false);
       });
+
+      testWidgets(
+          'Settings() - `persistenceEnabled` & `cacheSizeBytes` with acceptable number',
+          (widgetTester) async {
+        FirebaseFirestore.instance.settings =
+            const Settings(persistenceEnabled: true, cacheSizeBytes: 10000000);
+        // Used to trigger settings
+        await FirebaseFirestore.instance
+            .collection('flutter-tests')
+            .doc('new-doc')
+            .set(
+          {'some': 'data'},
+        );
+      });
+
+      testWidgets(
+          'Settings() - `persistenceEnabled` & `cacheSizeBytes` with `Settings.CACHE_SIZE_UNLIMITED`',
+          (widgetTester) async {
+        FirebaseFirestore.instance.settings = const Settings(
+          persistenceEnabled: true,
+          cacheSizeBytes: Settings.CACHE_SIZE_UNLIMITED,
+        );
+        // Used to trigger settings
+        await FirebaseFirestore.instance
+            .collection('flutter-tests')
+            .doc('new-doc')
+            .set(
+          {'some': 'data'},
+        );
+      });
+
+      testWidgets(
+          'Settings() - `persistenceEnabled` & without `cacheSizeBytes`',
+          (widgetTester) async {
+        FirebaseFirestore.instance.settings =
+            const Settings(persistenceEnabled: true);
+        // Used to trigger settings
+        await FirebaseFirestore.instance
+            .collection('flutter-tests')
+            .doc('new-doc')
+            .set(
+          {'some': 'data'},
+        );
+      });
     },
   );
 }

packages/cloud_firestore/cloud_firestore/ios/Classes/FLTFirebaseFirestoreReader.m

@@ -95,14 +95,20 @@ - (FIRFirestoreSettings *)FIRFirestoreSettings {
 
   if (![values[@"persistenceEnabled"] isEqual:[NSNull null]]) {
     bool persistEnabled = [((NSNumber *)values[@"persistenceEnabled"]) boolValue];
-    int size = [((NSNumber *)values[@"cacheSizeBytes"]) intValue];
+
+    // This is the maximum amount of cache allowed. We use the same number on android.
+    // This now causes an exception: kFIRFirestoreCacheSizeUnlimited
+    NSNumber *size = @104857600;
+
+    if (![values[@"cacheSizeBytes"] isEqual:[NSNull null]]) {
+      NSNumber *cacheSizeBytes = ((NSNumber *)values[@"cacheSizeBytes"]);
+      if ([cacheSizeBytes intValue] != -1) {
+        size = cacheSizeBytes;
+      }
+    }
 
     if (persistEnabled) {
-      NSNumber *unlimitedPersistence =
-          [NSNumber numberWithLongLong:kFIRFirestoreCacheSizeUnlimited];
-      settings.cacheSettings = [[FIRPersistentCacheSettings alloc]
-          initWithSizeBytes:size == -1 ? unlimitedPersistence
-                                       : ((NSNumber *)values[@"cacheSizeBytes"])];
+      settings.cacheSettings = [[FIRPersistentCacheSettings alloc] initWithSizeBytes:size];
     } else {
       settings.cacheSettings = [[FIRMemoryCacheSettings alloc]
           initWithGarbageCollectorSettings:[[FIRMemoryLRUGCSettings alloc] init]];

packages/cloud_firestore/cloud_firestore/test/query_test.dart

@@ -403,5 +403,36 @@ void main() {
         );
       });
     });
+
+    group('Settings()', () {
+      test('Test the assert for setting `cacheSizeBytes` minimum and maximum',
+          () {
+        void configureCache(int? cacheSizeBytes) {
+          assert(
+            cacheSizeBytes == null ||
+                cacheSizeBytes == Settings.CACHE_SIZE_UNLIMITED ||
+                (cacheSizeBytes >= 1048576 && cacheSizeBytes <= 104857600),
+            'Cache size, if specified, must be either CACHE_SIZE_UNLIMITED or between 1048576 bytes (inclusive) and 104857600 bytes (inclusive).',
+          );
+        }
+
+        // Happy paths
+        expect(() => configureCache(null), returnsNormally);
+        expect(
+          () => configureCache(Settings.CACHE_SIZE_UNLIMITED),
+          returnsNormally,
+        );
+        expect(() => configureCache(5000000), returnsNormally);
+        expect(() => configureCache(1048577), returnsNormally);
+        expect(() => configureCache(104857600), returnsNormally);
+        expect(() => configureCache(104857500), returnsNormally);
+
+        // Assertion triggers
+        expect(() => configureCache(1), throwsA(isA<AssertionError>()));
+        expect(() => configureCache(1000), throwsA(isA<AssertionError>()));
+        expect(() => configureCache(200000000), throwsA(isA<AssertionError>()));
+        expect(() => configureCache(500000), throwsA(isA<AssertionError>()));
+      });
+    });
   });
 }

packages/cloud_firestore/cloud_firestore_platform_interface/lib/src/settings.dart

@@ -69,15 +69,23 @@ class Settings {
     bool? sslEnabled,
     int? cacheSizeBytes,
     bool? ignoreUndefinedProperties,
-  }) =>
-      Settings(
-        persistenceEnabled: persistenceEnabled ?? this.persistenceEnabled,
-        host: host ?? this.host,
-        sslEnabled: sslEnabled ?? this.sslEnabled,
-        cacheSizeBytes: cacheSizeBytes ?? this.cacheSizeBytes,
-        ignoreUndefinedProperties:
-            ignoreUndefinedProperties ?? this.ignoreUndefinedProperties,
-      );
+  }) {
+    assert(
+        cacheSizeBytes == null ||
+            cacheSizeBytes == CACHE_SIZE_UNLIMITED ||
+            // 1mb and 100mb. minimum and maximum inclusive range.
+            (cacheSizeBytes >= 1048576 && cacheSizeBytes <= 104857600),
+        'Cache size must be between 1048576 bytes (inclusive) and 104857600 bytes (inclusive)');
+
+    return Settings(
+      persistenceEnabled: persistenceEnabled ?? this.persistenceEnabled,
+      host: host ?? this.host,
+      sslEnabled: sslEnabled ?? this.sslEnabled,
+      cacheSizeBytes: cacheSizeBytes ?? this.cacheSizeBytes,
+      ignoreUndefinedProperties:
+          ignoreUndefinedProperties ?? this.ignoreUndefinedProperties,
+    );
+  }
 
   @override
   bool operator ==(Object other) =>