From 84b0bb3d1c5b76188ceebcbc4c244878f84c52c1 Mon Sep 17 00:00:00 2001
From: Craig Tiller <ctiller@google.com>
Date: Thu, 22 Feb 2024 08:39:53 -0800
Subject: [PATCH] [call-v3] Add an opt-out for call-v3 stack instantiation
 (#35956)

We've got a few filters in prod that are going to be awful to convert, and are getting pulled into some unit tests in hard to disable ways -- buuut we don't need them for chaotic good in the reality in which we're deploying it -- so I want an escape hatch for the moment.

Closes #35956

COPYBARA_INTEGRATE_REVIEW=https://github.com/grpc/grpc/pull/35956 from ctiller:not-now-thanks f5d331b9233437e19880ac92f857a1076e7a1a18
PiperOrigin-RevId: 609384999
---
 src/core/lib/channel/promise_based_filter.h | 60 +++++++++++++++++++--
 1 file changed, 57 insertions(+), 3 deletions(-)

diff --git a/src/core/lib/channel/promise_based_filter.h b/src/core/lib/channel/promise_based_filter.h
index cef590ef4ef..bb642bc7f21 100644
--- a/src/core/lib/channel/promise_based_filter.h
+++ b/src/core/lib/channel/promise_based_filter.h
@@ -74,6 +74,12 @@
 
 namespace grpc_core {
 
+// HACK: If a filter has this type as a base class it will be skipped in
+// v3 filter stacks. This is a temporary measure to allow the v3 filter stack
+// to be bought up whilst some tests inadvertently rely on hard to convert
+// filters.
+class HackyHackyHackySkipInV3FilterStacks {};
+
 class ChannelFilter {
  public:
   class Args {
@@ -1906,9 +1912,11 @@ struct ChannelFilterWithFlagsMethods {
 //       ChannelArgs channel_args, ChannelFilter::Args filter_args);
 // };
 template <typename F, FilterEndpoint kEndpoint, uint8_t kFlags = 0>
-absl::enable_if_t<std::is_base_of<ChannelFilter, F>::value &&
-                      !std::is_base_of<ImplementChannelFilter<F>, F>::value,
-                  grpc_channel_filter>
+absl::enable_if_t<
+    std::is_base_of<ChannelFilter, F>::value &&
+        !std::is_base_of<ImplementChannelFilter<F>, F>::value &&
+        !std::is_base_of<HackyHackyHackySkipInV3FilterStacks, F>::value,
+    grpc_channel_filter>
 MakePromiseBasedFilter(const char* name) {
   using CallData = promise_filter_detail::CallData<kEndpoint>;
 
@@ -1946,6 +1954,52 @@ MakePromiseBasedFilter(const char* name) {
   };
 }
 
+template <typename F, FilterEndpoint kEndpoint, uint8_t kFlags = 0>
+absl::enable_if_t<
+    std::is_base_of<HackyHackyHackySkipInV3FilterStacks, F>::value,
+    grpc_channel_filter>
+MakePromiseBasedFilter(const char* name) {
+  using CallData = promise_filter_detail::CallData<kEndpoint>;
+
+  return grpc_channel_filter{
+      // start_transport_stream_op_batch
+      promise_filter_detail::BaseCallDataMethods::StartTransportStreamOpBatch,
+      // make_call_promise
+      promise_filter_detail::ChannelFilterMethods::MakeCallPromise,
+      [](grpc_channel_element* elem, CallSpineInterface*) {
+        GRPC_LOG_EVERY_N_SEC(
+            1, GPR_ERROR,
+            "gRPC V3 call stack in use, with a filter ('%s') that is not V3.",
+            elem->filter->name);
+      },
+      // start_transport_op
+      promise_filter_detail::ChannelFilterMethods::StartTransportOp,
+      // sizeof_call_data
+      sizeof(CallData),
+      // init_call_elem
+      promise_filter_detail::CallDataFilterWithFlagsMethods<
+          CallData, kFlags>::InitCallElem,
+      // set_pollset_or_pollset_set
+      promise_filter_detail::BaseCallDataMethods::SetPollsetOrPollsetSet,
+      // destroy_call_elem
+      promise_filter_detail::CallDataFilterWithFlagsMethods<
+          CallData, kFlags>::DestroyCallElem,
+      // sizeof_channel_data
+      sizeof(F),
+      // init_channel_elem
+      promise_filter_detail::ChannelFilterWithFlagsMethods<
+          F, kFlags>::InitChannelElem,
+      // post_init_channel_elem
+      promise_filter_detail::ChannelFilterMethods::PostInitChannelElem,
+      // destroy_channel_elem
+      promise_filter_detail::ChannelFilterMethods::DestroyChannelElem,
+      // get_channel_info
+      promise_filter_detail::ChannelFilterMethods::GetChannelInfo,
+      // name
+      name,
+  };
+}
+
 template <typename F, FilterEndpoint kEndpoint, uint8_t kFlags = 0>
 absl::enable_if_t<std::is_base_of<ImplementChannelFilter<F>, F>::value,
                   grpc_channel_filter>