Improve promise-based-filter APIs (#28839)

* Improve promise-based-filter APIs

* review feedback

* comment

* fix

src/core/ext/filters/http/client_authority_filter.cc

@@ -71,7 +71,8 @@ ArenaPromise<TrailingMetadata> ClientAuthorityFilter::MakeCallPromise(
 
 namespace {
 const grpc_channel_filter grpc_client_authority_filter =
-    MakePromiseBasedFilter<ClientAuthorityFilter>();
+    MakePromiseBasedFilter<ClientAuthorityFilter, FilterEndpoint::kClient>(
+        "authority");
 
 bool add_client_authority_filter(ChannelStackBuilder* builder) {
   const grpc_channel_args* channel_args = builder->channel_args();

src/core/ext/filters/http/client_authority_filter.h

@@ -36,9 +36,6 @@ class ClientAuthorityFilter {
   static absl::StatusOr<ClientAuthorityFilter> Create(
       const grpc_channel_args* args);
 
-  static constexpr bool is_client() { return true; }
-  static constexpr const char* name() { return "authority"; }
-
   // Construct a promise for one call.
   ArenaPromise<TrailingMetadata> MakeCallPromise(
       ClientInitialMetadata initial_metadata,

src/core/lib/channel/promise_based_filter.h

@@ -35,6 +35,14 @@
 
 namespace grpc_core {
 
+// Designator for whether a filter is client side or server side.
+// Please don't use this outside calls to MakePromiseBasedFilter - it's intended
+// to be deleted once the promise conversion is complete.
+enum class FilterEndpoint {
+  kClient,
+  kServer,
+};
+
 namespace promise_filter_detail {
 
 // Call data shared between all implementations of promise-based filters.
@@ -77,12 +85,12 @@ class BaseCallData {
 // Specific call data per channel filter.
 // Note that we further specialize for clients and servers since their
 // implementations are very different.
-template <class ChannelFilter, bool kIsClient = ChannelFilter::is_client()>
+template <class ChannelFilter, FilterEndpoint endpoint>
 class CallData;
 
 // Client implementation of call data.
 template <class ChannelFilter>
-class CallData<ChannelFilter, true> : public BaseCallData {
+class CallData<ChannelFilter, FilterEndpoint::kClient> : public BaseCallData {
  public:
   CallData(grpc_call_element* elem, const grpc_call_element_args* args)
       : BaseCallData(elem, args) {
@@ -386,7 +394,7 @@ class CallData<ChannelFilter, true> : public BaseCallData {
 
 // Server implementation of call data.
 template <class ChannelFilter>
-class CallData<ChannelFilter, false> : public BaseCallData {
+class CallData<ChannelFilter, FilterEndpoint::kServer> : public BaseCallData {
  public:
   CallData(grpc_call_element* elem, const grpc_call_element_args* args)
       : BaseCallData(elem, args) {
@@ -661,8 +669,6 @@ class CallData<ChannelFilter, false> : public BaseCallData {
 // ChannelFilter contains the following:
 // class SomeChannelFilter {
 //  public:
-//   static constexpr bool is_client();
-//   static constexpr const char* name();
 //   static absl::StatusOr<SomeChannelFilter> Create(
 //       const grpc_channel_args* args);
 //   ArenaPromise<TrailingMetadata> MakeCallPromise(
@@ -670,9 +676,9 @@ class CallData<ChannelFilter, false> : public BaseCallData {
 // };
 // TODO(ctiller): allow implementing get_channel_info, start_transport_op in
 // some way on ChannelFilter.
-template <typename ChannelFilter>
-grpc_channel_filter MakePromiseBasedFilter() {
-  using CallData = promise_filter_detail::CallData<ChannelFilter>;
+template <typename ChannelFilter, FilterEndpoint kEndpoint>
+grpc_channel_filter MakePromiseBasedFilter(const char* name) {
+  using CallData = promise_filter_detail::CallData<ChannelFilter, kEndpoint>;
 
   return grpc_channel_filter{
       // start_transport_stream_op_batch
@@ -718,7 +724,7 @@ grpc_channel_filter MakePromiseBasedFilter() {
       // get_channel_info
       grpc_channel_next_get_info,
       // name
-      ChannelFilter::name(),
+      name,
   };
 }
 

src/core/lib/security/authorization/sdk_server_authz_filter.cc

@@ -107,6 +107,7 @@ ArenaPromise<TrailingMetadata> SdkServerAuthzFilter::MakeCallPromise(
 }
 
 const grpc_channel_filter SdkServerAuthzFilter::kFilterVtable =
-    MakePromiseBasedFilter<SdkServerAuthzFilter>();
+    MakePromiseBasedFilter<SdkServerAuthzFilter, FilterEndpoint::kServer>(
+        "sdk-server-authz");
 
 }  // namespace grpc_core

src/core/lib/security/authorization/sdk_server_authz_filter.h

@@ -29,9 +29,6 @@ class SdkServerAuthzFilter {
   static absl::StatusOr<SdkServerAuthzFilter> Create(
       const grpc_channel_args* args);
 
-  static constexpr bool is_client() { return false; }
-  static constexpr const char* name() { return "sdk-server-authz"; }
-
   ArenaPromise<TrailingMetadata> MakeCallPromise(
       ClientInitialMetadata initial_metadata,
       NextPromiseFactory next_promise_factory);

test/core/transport/chttp2/streams_not_seen_test.cc

@@ -61,11 +61,6 @@ class TrailingMetadataRecordingFilter {
     return TrailingMetadataRecordingFilter();
   }
 
-  static constexpr bool is_client() { return true; }
-  static constexpr const char* name() {
-    return "trailing-metadata-recording-filter";
-  }
-
   ArenaPromise<TrailingMetadata> MakeCallPromise(
       ClientInitialMetadata initial_metadata,
       NextPromiseFactory next_promise_factory) {
@@ -93,7 +88,9 @@ class TrailingMetadataRecordingFilter {
 };
 
 grpc_channel_filter TrailingMetadataRecordingFilter::kFilterVtable =
-    MakePromiseBasedFilter<TrailingMetadataRecordingFilter>();
+    MakePromiseBasedFilter<TrailingMetadataRecordingFilter,
+                           FilterEndpoint::kClient>(
+        "trailing-metadata-recording-filter");
 absl::optional<GrpcStreamNetworkState::ValueType>
     TrailingMetadataRecordingFilter::stream_network_state_;