Remove absl::optional from firestore::api (#8225)

Author: wu-hui

Firestore/Source/API/FIRFirestore.mm

@@ -435,14 +435,13 @@ - (FIRLoadBundleTask *)loadBundleStream:(NSInputStream *)bundleStream
 
 - (void)getQueryNamed:(NSString *)name completion:(void (^)(FIRQuery *_Nullable query))completion {
   auto firestore = _firestore;
-  auto callback = [completion, firestore](absl::optional<core::Query> query) {
+  auto callback = [completion, firestore](core::Query query, bool found) {
     if (!completion) {
       return;
     }
 
-    if (query.has_value()) {
-      FIRQuery *firQuery = [[FIRQuery alloc] initWithQuery:std::move(query.value())
-                                                 firestore:firestore];
+    if (found) {
+      FIRQuery *firQuery = [[FIRQuery alloc] initWithQuery:std::move(query) firestore:firestore];
       completion(firQuery);
     } else {
       completion(nil);

Firestore/core/src/api/api_fwd.h

@@ -53,7 +53,7 @@ using DocumentSnapshotListener =
 using QuerySnapshotListener =
     std::unique_ptr<core::EventListener<QuerySnapshot>>;
 
-using QueryCallback = std::function<void(absl::optional<core::Query>)>;
+using QueryCallback = std::function<void(core::Query, bool)>;
 
 }  // namespace api
 }  // namespace firestore

Firestore/core/src/core/firestore_client.cc

@@ -535,10 +535,12 @@ void FirestoreClient::GetNamedQuery(const std::string& name,
                         target.filters(), target.order_bys(), target.limit(),
                         named_query.value().bundled_query().limit_type(),
                         target.start_at(), target.end_at());
-            user_executor_->Execute(
-                [query, callback] { callback(std::move(query)); });
+            user_executor_->Execute([query, callback] {
+              callback(std::move(query), /*found=*/true);
+            });
           } else {
-            user_executor_->Execute([callback] { callback(absl::nullopt); });
+            user_executor_->Execute(
+                [callback] { callback(Query(), /*found=*/false); });
           }
         }
       };