Move proto_toolchain from rules_proto to protobuf

The toolchain type is consumed by proto_library and produced by proto_toolchain rule. As such it's a private dependency, because both rules are now part of protobuf repo.

There are some early adopters of --incompatible_enable_proto_toolchain_resolution that might be broken from this: grpc, rules_go, rules_ts, rules_rust, rules_lint, because they have implementation that is not using proto_common. Those repositories need to define their own proto_lang_toolchain and consume it with proto_common.compile.

PiperOrigin-RevId: 654897871

MODULE.bazel

@@ -27,9 +27,6 @@ bazel_dep(name = "platforms", version = "0.0.8")
 bazel_dep(name = "zlib", version = "1.3.1")
 bazel_dep(name = "bazel_features", version = "1.13.0", repo_name = "proto_bazel_features")
 
-# TODO: remove after toolchain types are moved to protobuf
-bazel_dep(name = "rules_proto", version = "4.0.0")
-
 SUPPORTED_PYTHON_VERSIONS = [
     "3.8",
     "3.9",
@@ -99,3 +96,5 @@ use_repo(maven, "maven")
 # Development dependencies
 bazel_dep(name = "googletest", version = "1.14.0", repo_name = "com_google_googletest", dev_dependency = True)
 bazel_dep(name = "rules_testing", version = "0.6.0", dev_dependency = True)
+# rules_proto are needed for @com_google_protobuf_v25.0 used in //compatibility/... tests
+bazel_dep(name = "rules_proto", version = "4.0.0", dev_dependency = True)

bazel/private/BUILD.bazel

@@ -10,6 +10,10 @@ load("//bazel/private:native_bool_flag.bzl", "native_bool_flag")
 
 licenses(["notice"])
 
+toolchain_type(
+    name = "proto_toolchain_type",
+)
+
 bzl_library(
     name = "upb_proto_library_internal_bzl",
     srcs = [
@@ -40,6 +44,11 @@ bzl_library(
         "proto_toolchain_rule.bzl",
     ],
     visibility = ["//bazel:__subpackages__"],
+    deps = [
+        ":toolchain_helpers_bzl",
+        "//bazel/common:proto_common_bzl",
+        "//bazel/common:proto_lang_toolchain_info_bzl",
+    ],
 )
 
 bzl_library(

bazel/private/proto_toolchain_rule.bzl

@@ -1,13 +1,9 @@
 """A Starlark implementation of the proto_toolchain rule."""
 
-load("//bazel/common:proto_common.bzl", "proto_common")
 load("//bazel/common:proto_lang_toolchain_info.bzl", "ProtoLangToolchainInfo")
+load("//bazel/private:toolchain_helpers.bzl", "toolchains")
 
 def _impl(ctx):
-    kwargs = {}
-    if getattr(proto_common, "INCOMPATIBLE_PASS_TOOLCHAIN_TYPE", False):
-        kwargs["toolchain_type"] = "@rules_proto//proto:toolchain_type"
-
     return [
         DefaultInfo(
             files = depset(),
@@ -23,7 +19,7 @@ def _impl(ctx):
                 protoc_opts = ctx.fragments.proto.experimental_protoc_opts,
                 progress_message = ctx.attr.progress_message,
                 mnemonic = ctx.attr.mnemonic,
-                **kwargs
+                toolchain_type = toolchains.PROTO_TOOLCHAIN,
             ),
         ),
     ]

bazel/private/toolchain_helpers.bzl

@@ -45,5 +45,5 @@ toolchains = struct(
     find_toolchain = _find_toolchain,
     if_legacy_toolchain = _if_legacy_toolchain,
     INCOMPATIBLE_ENABLE_PROTO_TOOLCHAIN_RESOLUTION = _incompatible_toolchain_resolution,
-    PROTO_TOOLCHAIN = "@rules_proto//proto:toolchain_type",
+    PROTO_TOOLCHAIN = "//bazel/private:proto_toolchain_type",
 )

bazel/toolchains/BUILD.bazel

@@ -8,6 +8,7 @@ bzl_library(
     visibility = ["//visibility:public"],
     deps = [
         "//bazel/private:proto_toolchain_rule_bzl",
+        "//bazel/private:toolchain_helpers_bzl",
     ],
 )
 

bazel/toolchains/proto_toolchain.bzl

@@ -4,6 +4,7 @@ The macro additionally creates toolchain target when toolchain_type is given.
 """
 
 load("//bazel/private:proto_toolchain_rule.bzl", _proto_toolchain_rule = "proto_toolchain")
+load("//bazel/private:toolchain_helpers.bzl", "toolchains")
 
 def proto_toolchain(*, name, proto_compiler, exec_compatible_with = []):
     """Creates a proto_toolchain and toolchain target for proto_library.
@@ -19,7 +20,7 @@ def proto_toolchain(*, name, proto_compiler, exec_compatible_with = []):
 
     native.toolchain(
         name = name + "_toolchain",
-        toolchain_type = "@rules_proto//proto:toolchain_type",
+        toolchain_type = toolchains.PROTO_TOOLCHAIN,
         exec_compatible_with = exec_compatible_with,
         target_compatible_with = [],
         toolchain = name,

protobuf_deps.bzl

@@ -120,17 +120,6 @@ def protobuf_deps():
                 sha256 = "160d1ebf33763124766fb35316329d907ca67f733238aa47624a8e3ff3cf2ef4",
             )
 
-    # TODO: remove after toolchain types are moved to protobuf
-    if not native.existing_rule("rules_proto"):
-        http_archive(
-            name = "rules_proto",
-            sha256 = "dc3fb206a2cb3441b485eb1e423165b231235a1ea9b031b4433cf7bc1fa460dd",
-            strip_prefix = "rules_proto-5.3.0-21.7",
-            urls = [
-                "https://github.com/bazelbuild/rules_proto/archive/refs/tags/5.3.0-21.7.tar.gz",
-            ],
-        )
-
     if not native.existing_rule("proto_bazel_features"):
         proto_bazel_features(name = "proto_bazel_features")