Support automatic exec groups in proto_common.compile

Pass toolchain_type through ProtoLangToolchainInfo into proto_common.compile and use it on ctx.actions.run. Automatic exec groups require that toolchain type is set on the `ctx.actions.run`. This information is used to select correct execution platform.

Expose INCOMPATIBLE_ENABLE_PROTO_TOOLCHAIN_RESOLUTION in proto_common. This will be needed to support lang_proto_libraries that are not part of Bazel. For example py_proto_library. Other methods in `toolchains` struct in proto_common.bzl, are both temporary and can be written in Starlark, so don't expose them. It's possible to access the value in backward compatible manner (that is with `getattr(proto_common, ...)`).

Expose INCOMPATIBLE_PASS_TOOLCHAIN_TYPE in proto_common. Second "flag" is here to mark, that builtin `proto_lang_toolchain` rule has a `toolchain_type` attribute. This way `proto_lang_toolchain` macro can pass the value in a compatible fashion with older Bazel. This should make toolchainisation work with older versions of Bazel that don't know about automatic exec groups and don't need to pass in the value.

Issue: bazelbuild/rules_proto#179
PiperOrigin-RevId: 571876657
Change-Id: I543ab862b318c9062d40430160e33ad197973094

src/main/starlark/builtins_bzl/common/proto/proto_common.bzl

@@ -30,6 +30,7 @@ ProtoLangToolchainInfo = provider(
         protoc_opts = "(list[str]) Options to pass to proto compiler.",
         progress_message = "(str) Progress message to set on the proto compiler action.",
         mnemonic = "(str) Mnemonic to set on the proto compiler action.",
+        toolchain_type = """(Label) Toolchain type that was used to obtain this info""",
     ),
 )
 
@@ -154,6 +155,7 @@ def _compile(
         use_default_shell_env = True,
         resource_set = resource_set,
         exec_group = experimental_exec_group,
+        toolchain = getattr(proto_lang_toolchain_info, "toolchain_type", None),
     )
 
 _BAZEL_TOOLS_PREFIX = "external/bazel_tools/"
@@ -290,7 +292,6 @@ toolchains = struct(
     use_toolchain = _use_toolchain,
     find_toolchain = _find_toolchain,
     if_legacy_toolchain = _if_legacy_toolchain,
-    INCOMPATIBLE_ENABLE_PROTO_TOOLCHAIN_RESOLUTION = _builtins.toplevel.proto_common.incompatible_enable_proto_toolchain_resolution(),
 )
 
 proto_common_do_not_use = struct(
@@ -299,4 +300,6 @@ proto_common_do_not_use = struct(
     experimental_should_generate_code = _experimental_should_generate_code,
     experimental_filter_sources = _experimental_filter_sources,
     ProtoLangToolchainInfo = ProtoLangToolchainInfo,
+    INCOMPATIBLE_ENABLE_PROTO_TOOLCHAIN_RESOLUTION = _builtins.toplevel.proto_common.incompatible_enable_proto_toolchain_resolution(),
+    INCOMPATIBLE_PASS_TOOLCHAIN_TYPE = True,
 )

src/main/starlark/builtins_bzl/common/proto/proto_lang_toolchain.bzl

@@ -14,7 +14,7 @@
 
 """A Starlark implementation of the proto_lang_toolchain rule."""
 
-load(":common/proto/proto_common.bzl", "ProtoLangToolchainInfo", "toolchains")
+load(":common/proto/proto_common.bzl", "ProtoLangToolchainInfo", "toolchains", proto_common = "proto_common_do_not_use")
 load(":common/proto/proto_semantics.bzl", "semantics")
 
 ProtoInfo = _builtins.toplevel.ProtoInfo
@@ -31,7 +31,7 @@ def _rule_impl(ctx):
     if ctx.attr.plugin != None:
         plugin = ctx.attr.plugin[DefaultInfo].files_to_run
 
-    if toolchains.INCOMPATIBLE_ENABLE_PROTO_TOOLCHAIN_RESOLUTION:
+    if proto_common.INCOMPATIBLE_ENABLE_PROTO_TOOLCHAIN_RESOLUTION:
         proto_compiler = ctx.toolchains[semantics.PROTO_TOOLCHAIN].proto.proto_compiler
         protoc_opts = ctx.toolchains[semantics.PROTO_TOOLCHAIN].proto.protoc_opts
     else:
@@ -49,6 +49,7 @@ def _rule_impl(ctx):
         protoc_opts = protoc_opts,
         progress_message = ctx.attr.progress_message,
         mnemonic = ctx.attr.mnemonic,
+        toolchain_type = ctx.attr.toolchain_type.label if ctx.attr.toolchain_type else None,
     )
     return [
         DefaultInfo(files = depset(), runfiles = ctx.runfiles()),
@@ -74,7 +75,8 @@ proto_lang_toolchain = rule(
             "blacklisted_protos": attr.label_list(
                 providers = [ProtoInfo],
             ),
-        } | ({} if toolchains.INCOMPATIBLE_ENABLE_PROTO_TOOLCHAIN_RESOLUTION else {
+            "toolchain_type": attr.label(),
+        } | ({} if proto_common.INCOMPATIBLE_ENABLE_PROTO_TOOLCHAIN_RESOLUTION else {
             "_proto_compiler": attr.label(
                 cfg = "exec",
                 executable = True,

src/main/starlark/builtins_bzl/common/proto/proto_library.bzl

@@ -251,7 +251,7 @@ def _write_descriptor_set(ctx, direct_sources, deps, exports, proto_info, descri
             args.add("--allowed_public_imports=")
         else:
             args.add_joined("--allowed_public_imports", public_import_protos, map_each = _get_import_path, join_with = ":")
-    if toolchains.INCOMPATIBLE_ENABLE_PROTO_TOOLCHAIN_RESOLUTION:
+    if proto_common.INCOMPATIBLE_ENABLE_PROTO_TOOLCHAIN_RESOLUTION:
         toolchain = ctx.toolchains[semantics.PROTO_TOOLCHAIN]
         if not toolchain:
             fail("Protocol compiler toolchain could not be resolved.")

src/test/java/com/google/devtools/build/lib/packages/util/MockProtoSupport.java

@@ -268,6 +268,7 @@ public static void setupWorkspace(MockToolsConfig config) throws IOException {
         "        protoc_opts = ctx.fragments.proto.experimental_protoc_opts,",
         "        progress_message = ctx.attr.progress_message,",
         "        mnemonic = ctx.attr.mnemonic,",
+        "        toolchain_type = '//third_party/bazel_rules/rules_proto/proto:toolchain_type'",
         "      ),",
         "    ),",
         "  ]",
@@ -293,7 +294,7 @@ public static void setupWorkspace(MockToolsConfig config) throws IOException {
         "third_party/bazel_rules/rules_proto/proto/proto_lang_toolchain.bzl",
         "def proto_lang_toolchain(*, name, toolchain_type = None, exec_compatible_with = [],",
         "         target_compatible_with = [], **attrs):",
-        "  native.proto_lang_toolchain(name = name, **attrs)",
+        "  native.proto_lang_toolchain(name = name, toolchain_type = toolchain_type, **attrs)",
         "  if toolchain_type:",
         "    native.toolchain(",
         "      name = name + '_toolchain',",