fix: make it possible to add multiple mountingOverrideDelegates (#44927)

Summary:
PR changing the single mountingOverrideDelegate to a vector of those, so other listeners can operate on the transaction. Used by `react-native-screens` in software-mansion/react-native-screens#2134 and `react-native-reanimated` in software-mansion/react-native-reanimated#6055.

Till now, only one listener could be added there, meaning that e.g. `Layout Animations` from `react-native`,  `Layout Animations` from `react-native-reanimated` and listening for `Screen` removal in `react-native-screens` could not operate at the same time.

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[GENERAL] [FIXED] - Add option for multiple `mountingOverrideDelegates`

Pull Request resolved: #44927

Test Plan: The code of `LayoutAnimations` inside `react-native` should work the same since it will add just one listener then. For other cases, different libraries can read/mutate transactions.

Reviewed By: javache

Differential Revision: D58530278

Pulled By: sammy-SC

fbshipit-source-id: d6305963621000be11d51a50cffff64526cca934

packages/react-native/ReactCommon/react/renderer/mounting/MountingCoordinator.cpp

@@ -104,31 +104,33 @@ std::optional<MountingTransaction> MountingCoordinator::pullTransaction()
   }
 
   // Override case
-  auto mountingOverrideDelegate = mountingOverrideDelegate_.lock();
-  auto shouldOverridePullTransaction = mountingOverrideDelegate &&
-      mountingOverrideDelegate->shouldOverridePullTransaction();
-
-  if (shouldOverridePullTransaction) {
-    SystraceSection section2("MountingCoordinator::overridePullTransaction");
-
-    auto mutations = ShadowViewMutation::List{};
-    auto telemetry = TransactionTelemetry{};
-
-    if (transaction.has_value()) {
-      mutations = transaction->getMutations();
-      telemetry = transaction->getTelemetry();
-    } else {
-      number_++;
-      telemetry.willLayout();
-      telemetry.didLayout();
-      telemetry.willCommit();
-      telemetry.didCommit();
-      telemetry.willDiff();
-      telemetry.didDiff();
-    }
+  for (const auto& delegate : mountingOverrideDelegates_) {
+    auto mountingOverrideDelegate = delegate.lock();
+    auto shouldOverridePullTransaction = mountingOverrideDelegate &&
+        mountingOverrideDelegate->shouldOverridePullTransaction();
+
+    if (shouldOverridePullTransaction) {
+      SystraceSection section2("MountingCoordinator::overridePullTransaction");
+
+      auto mutations = ShadowViewMutation::List{};
+      auto telemetry = TransactionTelemetry{};
+
+      if (transaction.has_value()) {
+        mutations = transaction->getMutations();
+        telemetry = transaction->getTelemetry();
+      } else {
+        number_++;
+        telemetry.willLayout();
+        telemetry.didLayout();
+        telemetry.willCommit();
+        telemetry.didCommit();
+        telemetry.willDiff();
+        telemetry.didDiff();
+      }
 
-    transaction = mountingOverrideDelegate->pullTransaction(
-        surfaceId_, number_, telemetry, std::move(mutations));
+      transaction = mountingOverrideDelegate->pullTransaction(
+          surfaceId_, number_, telemetry, std::move(mutations));
+    }
   }
 
 #ifdef RN_SHADOW_TREE_INTROSPECTION
@@ -203,7 +205,8 @@ ShadowTreeRevision MountingCoordinator::getBaseRevision() const {
 void MountingCoordinator::setMountingOverrideDelegate(
     std::weak_ptr<const MountingOverrideDelegate> delegate) const {
   std::scoped_lock lock(mutex_);
-  mountingOverrideDelegate_ = std::move(delegate);
+  mountingOverrideDelegates_.insert(
+      mountingOverrideDelegates_.end(), std::move(delegate));
 }
 
 } // namespace facebook::react

packages/react-native/ReactCommon/react/renderer/mounting/MountingCoordinator.h

@@ -119,8 +119,8 @@ class MountingCoordinator final {
   mutable std::optional<ShadowTreeRevision> lastRevision_{};
   mutable MountingTransaction::Number number_{0};
   mutable std::condition_variable signal_;
-  mutable std::weak_ptr<const MountingOverrideDelegate>
-      mountingOverrideDelegate_;
+  mutable std::vector<std::weak_ptr<const MountingOverrideDelegate>>
+      mountingOverrideDelegates_;
 
   TelemetryController telemetryController_;