feat(firestore): add client language support for Firestore plugin on Android and iOS

packages/cloud_firestore/cloud_firestore/android/src/main/java/io/flutter/plugins/firebase/firestore/FlutterFirebaseFirestorePlugin.java

@@ -8,6 +8,7 @@
 import static com.google.firebase.firestore.AggregateField.count;
 import static com.google.firebase.firestore.AggregateField.sum;
 
+import android.annotation.SuppressLint;
 import android.app.Activity;
 import android.util.Log;
 import androidx.annotation.NonNull;
@@ -33,6 +34,7 @@
 import com.google.firebase.firestore.Source;
 import com.google.firebase.firestore.Transaction;
 import com.google.firebase.firestore.WriteBatch;
+import com.google.firebase.firestore.remote.FirestoreChannel;
 import io.flutter.embedding.engine.plugins.FlutterPlugin;
 import io.flutter.embedding.engine.plugins.activity.ActivityAware;
 import io.flutter.embedding.engine.plugins.activity.ActivityPluginBinding;
@@ -129,9 +131,12 @@ private static void destroyCachedFirebaseFirestoreInstanceForKey(FirebaseFiresto
     }
   }
 
+  @SuppressLint("RestrictedApi")
   @Override
   public void onAttachedToEngine(@NonNull FlutterPluginBinding binding) {
     initInstance(binding.getBinaryMessenger());
+    FirestoreChannel.setClientLanguage(
+        "gl-dart/" + io.flutter.plugins.firebase.firestore.BuildConfig.LIBRARY_VERSION);
   }
 
   @Override

packages/cloud_firestore/cloud_firestore/ios/cloud_firestore.podspec

@@ -24,7 +24,7 @@ Pod::Spec.new do |s|
   s.license          = { :file => '../LICENSE' }
   s.authors          = 'The Chromium Authors'
   s.source           = { :path => '.' }
-  s.source_files     = 'cloud_firestore/Sources/cloud_firestore/**/*.{h,m}'
+  s.source_files     = 'cloud_firestore/Sources/cloud_firestore/**/*.{h,m,mm}'
   s.public_header_files = 'cloud_firestore/Sources/cloud_firestore/include/Public/**/*.h'
   s.private_header_files = 'cloud_firestore/Sources/cloud_firestore/include/Private/**/*.h'
 

packages/cloud_firestore/cloud_firestore/ios/cloud_firestore/Sources/cloud_firestore/FLTFirebaseFirestorePlugin.m

@@ -33,6 +33,10 @@
 NSString *const kFLTFirebaseFirestoreLoadBundleChannelName =
     @"plugins.flutter.io/firebase_firestore/loadBundle";
 
+@interface FLTFirestoreClientLanguage : NSObject
++ (void)setClientLanguage:(NSString *)language;
+@end
+
 @interface FLTFirebaseFirestorePlugin ()
 @property(nonatomic, retain) NSMutableDictionary *transactions;
 
@@ -122,6 +126,10 @@ - (instancetype)init:(NSObject<FlutterBinaryMessenger> *)messenger {
 + (void)registerWithRegistrar:(NSObject<FlutterPluginRegistrar> *)registrar {
   FLTFirebaseFirestorePlugin *instance =
       [[FLTFirebaseFirestorePlugin alloc] init:[registrar messenger]];
+#if TARGET_OS_IPHONE
+  [FLTFirestoreClientLanguage
+      setClientLanguage:[NSString stringWithFormat:@"gl-dart/%@", @LIBRARY_VERSION]];
+#endif
 
 #if TARGET_OS_OSX
 // TODO(Salakar): Publish does not exist on MacOS version of FlutterPluginRegistrar.

packages/cloud_firestore/cloud_firestore/ios/cloud_firestore/Sources/cloud_firestore/FLTFirestoreClientLanguage.mm

@@ -0,0 +1,33 @@
+// Copyright 2025 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#import <Foundation/Foundation.h>
+#import <string>
+
+namespace firebase {
+namespace firestore {
+namespace api {
+
+class Firestore {
+ public:
+  static void SetClientLanguage(std::string language_token);
+};
+
+}  // namespace api
+}  // namespace firestore
+}  // namespace firebase
+
+@interface FLTFirestoreClientLanguage : NSObject
++ (void)setClientLanguage:(NSString *)language;
+@end
+
+@implementation FLTFirestoreClientLanguage
++ (void)setClientLanguage:(NSString *)language {
+  if (language == nil) {
+    return;
+  }
+  std::string token = std::string([language UTF8String]);
+  firebase::firestore::api::Firestore::SetClientLanguage(token);
+}
+@end