Add an experimental gencode plugin

Makefile

@@ -154,9 +154,10 @@ checkgenerate:
 	@# Used in CI to verify that `make generate` doesn't produce a diff.
 	git --no-pager diff --exit-code >&2
 
-internal/gen/*/*.pb.go: $(BIN)/buf internal/proto/*/*/*.proto internal/proto/*/*/*/*.proto
+internal/gen/*/*.pb.go: $(BIN)/buf internal/proto/*/*/*.proto internal/proto/*/*/*/*.proto internal/gencode/* internal/gencode/generator/*
 	$(BIN)/buf generate --clean
 	$(BIN)/buf generate --template buf.gen.vt.yaml
+	$(BIN)/buf generate --template buf.gen.hyperpb.yaml
 
 .PHONY: $(BIN)/hypertest
 $(BIN)/hypertest: generate

buf.gen.hyperpb.yaml

@@ -0,0 +1,12 @@
+version: v2
+managed:
+  enabled: true
+  override:
+   - file_option: go_package_prefix
+     value: buf.build/go/hyperpb/internal/gen
+plugins:
+  - local: ["go", "run", "./cmd/protoc-gen-hyperpb"]
+    out: internal/gen
+    opt: paths=source_relative
+inputs:
+  - directory: internal/proto/test

cmd/protoc-gen-hyperpb/export/export.go

@@ -0,0 +1,43 @@
+// Copyright 2025 Buf Technologies, Inc.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+// Package export contains exported types and functions for use by gencode.
+//
+// Importing this package outside of the gencode voids any API compatibility
+// guarantees.
+package export
+
+import (
+	"google.golang.org/protobuf/reflect/protoreflect"
+
+	"buf.build/go/hyperpb/internal/gencode"
+	"buf.build/go/hyperpb/internal/tdp/repeated"
+	"buf.build/go/hyperpb/internal/xunsafe"
+)
+
+type (
+	DoNotImplement = gencode.DoNotImplement
+	Type           = gencode.Type
+	UnsafeMessage  = gencode.UnsafeMessage
+)
+
+func Reflect[P gencode.Message[M], M any](m P) protoreflect.Message { return gencode.Reflect(m) }
+
+func CastRepeatedEnum[E ~int32](r *repeated.Scalars[byte, protoreflect.EnumNumber]) *repeated.Scalars[byte, E] {
+	return xunsafe.Cast[repeated.Scalars[byte, E]](r)
+}
+
+func CastRepeatedMessage[P gencode.Message[M], M any](r *repeated.UntypedMessages) *repeated.Messages[M, P] {
+	return xunsafe.Cast[repeated.Messages[M, P]](r)
+}

cmd/protoc-gen-hyperpb/main.go

@@ -0,0 +1,34 @@
+// Copyright 2025 Buf Technologies, Inc.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+// Binary protoc-gen-hyperpb is a protoc plugin that generates Protobuf APIs for
+// working with specific hyperpb-compiled messages without reflection.
+//
+// The generated API follows, but is not a drop-in replacement for, the opaque
+// Go API, particularly returning non-slice values for accessing repeated
+// fields.
+//
+// All message types emitted by this generator export the full interface of
+// [hyperpb.Message], which can be used to access optimized operations, such
+// as [hyperpb.Message.Unmarshal].
+package main
+
+import (
+	"buf.build/go/hyperpb"
+	"buf.build/go/hyperpb/internal/gencode/generator"
+)
+
+func main() { generator.Main() }
+
+var _ hyperpb.Message // For documentation links.