Support --incompatible_enable_proto_toolchain_resolution

.github/workflows/test_bazel.yml

@@ -29,14 +29,21 @@ jobs:
         runner: [ ubuntu, windows, macos ]
         bazelversion: [ '7.1.2' ]
         bzlmod: [true, false ]
+        toolchain_resolution: [false ]
         include:
           - runner: ubuntu
             bazelversion: '6.4.0'
             # Not running Bazel 6 with bzlmod, because it doesn't support use_repo_rule in rules_jvm_external
             bzlmod: false
             continuous-only: true
+          - runner: ubuntu
+            bzlmod: false
+            toolchain_resolution: true
+          - runner: ubuntu
+            bzlmod: true
+            toolchain_resolution: true
     runs-on: ${{ matrix.runner }}-latest
-    name: ${{ matrix.continuous-only && inputs.continuous-prefix || '' }} Examples ${{ matrix.runner }} ${{ matrix.bazelversion }}${{ matrix.bzlmod && ' (bzlmod)' || '' }}
+    name: ${{ matrix.continuous-only && inputs.continuous-prefix || '' }} Examples ${{ matrix.runner }} ${{ matrix.bazelversion }}${{ matrix.bzlmod && ' (bzlmod)' || '' }} ${{ matrix.toolchain_resolution && ' (toolchain resolution)' || '' }}
     steps:
       - name: Checkout pending changes
         if: ${{ !matrix.continuous-only || inputs.continuous-run }}
@@ -63,4 +70,4 @@ jobs:
           credentials: ${{ secrets.GAR_SERVICE_ACCOUNT }}
           bazel-cache: examples
           version: ${{ matrix.bazelversion }}
-          bash: cd examples && bazel build //... $BAZEL_FLAGS --enable_bzlmod=${{ matrix.bzlmod }}
+          bash: cd examples && bazel build //... $BAZEL_FLAGS --enable_bzlmod=${{ matrix.bzlmod }} --incompatible_enable_proto_toolchain_resolution=${{ matrix.toolchain_resolution }}

MODULE.bazel

@@ -89,6 +89,9 @@ bazel_dep(
     repo_name = "proto_bazel_features",
 )
 
+# Proto toolchains
+register_toolchains("//bazel/private/toolchains:all")
+
 SUPPORTED_PYTHON_VERSIONS = [
     "3.8",
     "3.9",

bazel/common/proto_common.bzl

@@ -9,6 +9,7 @@
 
 load("@proto_bazel_features//:features.bzl", "bazel_features")
 load("//bazel/common:proto_lang_toolchain_info.bzl", "ProtoLangToolchainInfo")
+load("//bazel/private:native.bzl", "native_proto_common")
 load("//bazel/private:toolchain_helpers.bzl", "toolchains")
 
 def _import_virtual_proto_path(path):
@@ -347,5 +348,8 @@ proto_common = struct(
     get_import_path = _get_import_path,
     ProtoLangToolchainInfo = ProtoLangToolchainInfo,
     INCOMPATIBLE_ENABLE_PROTO_TOOLCHAIN_RESOLUTION = toolchains.INCOMPATIBLE_ENABLE_PROTO_TOOLCHAIN_RESOLUTION,
-    INCOMPATIBLE_PASS_TOOLCHAIN_TYPE = True,
+    INCOMPATIBLE_PASS_TOOLCHAIN_TYPE = (
+        getattr(native_proto_common, "INCOMPATIBLE_PASS_TOOLCHAIN_TYPE", False) or
+        not hasattr(native_proto_common, "ProtoLangToolchainInfo")
+    ),
 )

bazel/private/BUILD

@@ -5,6 +5,22 @@ package(default_applicable_licenses = ["//:license"])
 
 toolchain_type(
     name = "proto_toolchain_type",
+    visibility = ["//visibility:public"],
+)
+
+toolchain_type(
+    name = "cc_toolchain_type",
+    visibility = ["//visibility:public"],
+)
+
+toolchain_type(
+    name = "java_toolchain_type",
+    visibility = ["//visibility:public"],
+)
+
+toolchain_type(
+    name = "javalite_toolchain_type",
+    visibility = ["//visibility:public"],
 )
 
 toolchain_type(

bazel/private/bazel_cc_proto_library.bzl

@@ -13,7 +13,7 @@ load("//bazel/common:proto_info.bzl", "ProtoInfo")
 load("//bazel/private:cc_proto_support.bzl", "cc_proto_compile_and_link")
 load("//bazel/private:toolchain_helpers.bzl", "toolchains")
 
-_CC_PROTO_TOOLCHAIN = "@rules_cc//cc/proto:toolchain_type"
+_CC_PROTO_TOOLCHAIN = "//bazel/private:cc_toolchain_type"
 
 _ProtoCcFilesInfo = provider(fields = ["files"], doc = "Provide cc proto files.")
 _ProtoCcHeaderInfo = provider(fields = ["headers"], doc = "Provide cc proto headers.")

bazel/private/bazel_java_proto_library_rule.bzl

@@ -12,8 +12,7 @@ load("//bazel/common:proto_info.bzl", "ProtoInfo")
 load("//bazel/private:java_proto_support.bzl", "java_compile_for_protos", "java_info_merge_for_protos")
 load("//bazel/private:toolchain_helpers.bzl", "toolchains")
 
-# TODO: replace with toolchain type located in protobuf
-_JAVA_PROTO_TOOLCHAIN = "@rules_java//java/proto:toolchain_type"
+_JAVA_PROTO_TOOLCHAIN = "//bazel/private:java_toolchain_type"
 
 # The provider is used to collect source and runtime jars in the `proto_library` dependency graph.
 JavaProtoAspectInfo = provider("JavaProtoAspectInfo", fields = ["jars"])

bazel/private/java_lite_proto_library.bzl

@@ -16,8 +16,7 @@ load("//bazel/private:toolchain_helpers.bzl", "toolchains")
 
 _PROTO_TOOLCHAIN_ATTR = "_aspect_proto_toolchain_for_javalite"
 
-# TODO: replace with toolchain type located in protobuf
-_JAVA_LITE_PROTO_TOOLCHAIN = "@rules_java//java/proto:lite_toolchain_type"
+_JAVA_LITE_PROTO_TOOLCHAIN = "//bazel/private:javalite_toolchain_type"
 
 def _aspect_impl(target, ctx):
     """Generates and compiles Java code for a proto_library dependency graph.

bazel/private/proto_toolchain_rule.bzl

@@ -7,6 +7,7 @@
 #
 """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")
 
@@ -26,7 +27,7 @@ def _impl(ctx):
                 protoc_opts = ctx.fragments.proto.experimental_protoc_opts,
                 progress_message = ctx.attr.progress_message,
                 mnemonic = ctx.attr.mnemonic,
-                toolchain_type = toolchains.PROTO_TOOLCHAIN,
+                **(dict(toolchain_type = toolchains.PROTO_TOOLCHAIN) if proto_common.INCOMPATIBLE_PASS_TOOLCHAIN_TYPE else {})
             ),
         ),
     ]

bazel/private/toolchains/BUILD.bazel

@@ -0,0 +1,48 @@
+load("//bazel/toolchains:proto_lang_toolchain.bzl", "proto_lang_toolchain")
+load("//bazel/toolchains:proto_toolchain.bzl", "proto_toolchain")
+
+# Keep this file as small as possible and free of any unnecessary loads
+# It is loaded by every use of protobuf repository, and loads here can force
+# fetching of additional external repositories
+
+# It's also intentionally using toolchain instead of proto_lang_toolchain,
+# because the former does not resolve dependencies until toolchain resolution
+# needs them
+
+proto_toolchain(
+    name = "protoc_sources",
+    exec_compatible_with = [],
+    proto_compiler = "//:protoc",
+)
+
+toolchain(
+    name = "cc_source_toolchain",
+    exec_compatible_with = [],
+    target_compatible_with = [],
+    toolchain = "//:cc_toolchain",
+    toolchain_type = "//bazel/private:cc_toolchain_type",
+)
+
+toolchain(
+    name = "java_source_toolchain",
+    exec_compatible_with = [],
+    target_compatible_with = [],
+    toolchain = "//java/core:toolchain",
+    toolchain_type = "//bazel/private:java_toolchain_type",
+)
+
+toolchain(
+    name = "javalite_source_toolchain",
+    exec_compatible_with = [],
+    target_compatible_with = [],
+    toolchain = "//java/lite:toolchain",
+    toolchain_type = "//bazel/private:javalite_toolchain_type",
+)
+
+toolchain(
+    name = "python_source_toolchain",
+    exec_compatible_with = [],
+    target_compatible_with = [],
+    toolchain = "//python:python_toolchain",
+    toolchain_type = "//bazel/private:python_toolchain_type",
+)

protobuf_deps.bzl

@@ -200,3 +200,4 @@ def protobuf_deps():
         name = "nuget_python_x86-64_3.10.0",
         sha256 = "4474c83c25625d93e772e926f95f4cd398a0abbb52793625fa30f39af3d2cc00",
     )
+    native.register_toolchains("//bazel/private/toolchains:all")