From d5905834569d2d3c53e80722e4389cf03d689132 Mon Sep 17 00:00:00 2001
From: Yash Tibrewal <yashkt@google.com>
Date: Tue, 18 Dec 2018 12:10:20 -0800
Subject: Allow interceptor creators to return nullptr

---
 include/grpcpp/impl/codegen/client_interceptor.h | 15 +++++++++++++--
 include/grpcpp/impl/codegen/server_interceptor.h | 15 +++++++++++++--
 2 files changed, 26 insertions(+), 4 deletions(-)

(limited to 'include')

diff --git a/include/grpcpp/impl/codegen/client_interceptor.h b/include/grpcpp/impl/codegen/client_interceptor.h
index 2bae11a251..da75bde499 100644
--- a/include/grpcpp/impl/codegen/client_interceptor.h
+++ b/include/grpcpp/impl/codegen/client_interceptor.h
@@ -38,9 +38,17 @@ class InterceptorBatchMethodsImpl;
 namespace experimental {
 class ClientRpcInfo;
 
+// A factory interface for creation of client interceptors. A vector of
+// factories can be provided at channel creation which will be used to create a
+// new vector of client interceptors per RPC. Client interceptor authors should
+// create a subclass of ClientInterceptorFactorInterface which creates objects
+// of their interceptors.
 class ClientInterceptorFactoryInterface {
  public:
   virtual ~ClientInterceptorFactoryInterface() {}
+  // Returns a pointer to an Interceptor object on successful creation, nullptr
+  // otherwise. If nullptr is returned, this server interceptor factory is
+  // ignored for the purposes of that RPC.
   virtual Interceptor* CreateClientInterceptor(ClientRpcInfo* info) = 0;
 };
 }  // namespace experimental
@@ -120,8 +128,11 @@ class ClientRpcInfo {
     }
     for (auto it = creators.begin() + interceptor_pos; it != creators.end();
          ++it) {
-      interceptors_.push_back(std::unique_ptr<experimental::Interceptor>(
-          (*it)->CreateClientInterceptor(this)));
+      auto* interceptor = (*it)->CreateClientInterceptor(this);
+      if (interceptor != nullptr) {
+        interceptors_.push_back(
+            std::unique_ptr<experimental::Interceptor>(interceptor));
+      }
     }
     if (internal::g_global_client_interceptor_factory != nullptr) {
       interceptors_.push_back(std::unique_ptr<experimental::Interceptor>(
diff --git a/include/grpcpp/impl/codegen/server_interceptor.h b/include/grpcpp/impl/codegen/server_interceptor.h
index afc3c198cc..8652ec5c64 100644
--- a/include/grpcpp/impl/codegen/server_interceptor.h
+++ b/include/grpcpp/impl/codegen/server_interceptor.h
@@ -37,9 +37,17 @@ class InterceptorBatchMethodsImpl;
 namespace experimental {
 class ServerRpcInfo;
 
+// A factory interface for creation of server interceptors. A vector of
+// factories can be provided to ServerBuilder which will be used to create a new
+// vector of server interceptors per RPC. Server interceptor authors should
+// create a subclass of ServerInterceptorFactorInterface which creates objects
+// of their interceptors.
 class ServerInterceptorFactoryInterface {
  public:
   virtual ~ServerInterceptorFactoryInterface() {}
+  // Returns a pointer to an Interceptor object on successful creation, nullptr
+  // otherwise. If nullptr is returned, this server interceptor factory is
+  // ignored for the purposes of that RPC.
   virtual Interceptor* CreateServerInterceptor(ServerRpcInfo* info) = 0;
 };
 
@@ -90,8 +98,11 @@ class ServerRpcInfo {
           std::unique_ptr<experimental::ServerInterceptorFactoryInterface>>&
           creators) {
     for (const auto& creator : creators) {
-      interceptors_.push_back(std::unique_ptr<experimental::Interceptor>(
-          creator->CreateServerInterceptor(this)));
+      auto* interceptor = creator->CreateServerInterceptor(this);
+      if (interceptor != nullptr) {
+        interceptors_.push_back(
+            std::unique_ptr<experimental::Interceptor>(interceptor));
+      }
     }
   }
 
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