Create proto_toolchain rule

This change adds a new `proto_toolchain` rule which we will use later to resolve
tools and options required to compile Protocol Buffers, thus eventually replacing
some of the command-line options from `ProtoConfiguration`.

To preclude inconsistencies in the migration period, we will start with a
`proto_toolchain` rule that doesn't have any arguments and populate
its provider from the existing command-line options. After all consumers
have been migrated to resolve the tools from the toolchain instead of
reading the command-line, we will replace all proto-specific flags with
attributes on `proto_toolchain` (or similar, language-specific toolchains
for flags that only affect a specific language).

Updates bazelbuild#10005

src/main/java/com/google/devtools/build/lib/bazel/rules/BazelRuleClassProvider.java

@@ -106,6 +106,7 @@
 import com.google.devtools.build.lib.rules.proto.ProtoConfiguration;
 import com.google.devtools.build.lib.rules.proto.ProtoInfo;
 import com.google.devtools.build.lib.rules.proto.ProtoLangToolchainRule;
+import com.google.devtools.build.lib.rules.proto.ProtoToolchainRule;
 import com.google.devtools.build.lib.rules.python.PyInfo;
 import com.google.devtools.build.lib.rules.python.PyRuleClasses.PySymlink;
 import com.google.devtools.build.lib.rules.python.PyRuntimeInfo;
@@ -291,6 +292,7 @@ public void init(ConfiguredRuleClassProvider.Builder builder) {
           builder.addConfigurationFragment(new ProtoConfiguration.Loader());
           builder.addRuleDefinition(new BazelProtoLibraryRule());
           builder.addRuleDefinition(new ProtoLangToolchainRule());
+          builder.addRuleDefinition(new ProtoToolchainRule());
 
           ProtoBootstrap bootstrap =
               new ProtoBootstrap(

src/main/java/com/google/devtools/build/lib/bazel/rules/BazelRulesModule.java

@@ -476,6 +476,8 @@ public void initializeRuleClasses(ConfiguredRuleClassProvider.Builder builder) {
           ResourceFileLoader.loadResource(BazelRulesModule.class, "xcode_configure.WORKSPACE"));
       builder.addWorkspaceFileSuffix(
           ResourceFileLoader.loadResource(BazelShRuleClasses.class, "sh_configure.WORKSPACE"));
+      builder.addWorkspaceFileSuffix(
+          ResourceFileLoader.loadResource(BazelRulesModule.class, "proto.WORKSPACE"));
     } catch (IOException e) {
       throw new IllegalStateException(e);
     }

src/main/java/com/google/devtools/build/lib/bazel/rules/proto.WORKSPACE

@@ -0,0 +1 @@
+register_toolchains("@bazel_tools//tools/proto:toolchain")

src/main/java/com/google/devtools/build/lib/rules/proto/BUILD

@@ -40,6 +40,7 @@ java_library(
         "//src/main/java/com/google/devtools/build/lib/analysis:rule_definition_environment",
         "//src/main/java/com/google/devtools/build/lib/analysis:transitive_info_collection",
         "//src/main/java/com/google/devtools/build/lib/analysis:transitive_info_provider",
+        "//src/main/java/com/google/devtools/build/lib/analysis/platform",
         "//src/main/java/com/google/devtools/build/lib/analysis/stringtemplate",
         "//src/main/java/com/google/devtools/build/lib/cmdline",
         "//src/main/java/com/google/devtools/build/lib/collect/nestedset",

src/main/java/com/google/devtools/build/lib/rules/proto/ProtoToolchain.java

@@ -0,0 +1,38 @@
+// Copyright 2020 The Bazel Authors. All rights reserved.
+//
+// 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 com.google.devtools.build.lib.rules.proto;
+
+import com.google.devtools.build.lib.actions.MutableActionGraph.ActionConflictException;
+import com.google.devtools.build.lib.analysis.ConfiguredTarget;
+import com.google.devtools.build.lib.analysis.RuleConfiguredTargetBuilder;
+import com.google.devtools.build.lib.analysis.RuleConfiguredTargetFactory;
+import com.google.devtools.build.lib.analysis.RuleContext;
+import com.google.devtools.build.lib.analysis.Runfiles;
+import com.google.devtools.build.lib.analysis.RunfilesProvider;
+
+/** The implementation of the <code>proto_toolchain</code> rule. */
+public class ProtoToolchain implements RuleConfiguredTargetFactory {
+  @Override
+  public ConfiguredTarget create(RuleContext ruleContext)
+      throws ActionConflictException, RuleErrorException, InterruptedException {
+    ProtoToolchainInfo toolchain = new ProtoToolchainInfo();
+    RuleConfiguredTargetBuilder builder =
+        new RuleConfiguredTargetBuilder(ruleContext)
+            .addNativeDeclaredProvider(toolchain)
+            .addProvider(RunfilesProvider.class, RunfilesProvider.simple(Runfiles.EMPTY));
+
+    return builder.build();
+  }
+}

src/main/java/com/google/devtools/build/lib/rules/proto/ProtoToolchainInfo.java

@@ -0,0 +1,33 @@
+// Copyright 2020 The Bazel Authors. All rights reserved.
+//
+// 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 com.google.devtools.build.lib.rules.proto;
+
+import com.google.common.collect.ImmutableMap;
+import com.google.devtools.build.lib.analysis.platform.ToolchainInfo;
+import com.google.devtools.build.lib.concurrent.ThreadSafety.Immutable;
+import com.google.devtools.build.lib.skyframe.serialization.autocodec.AutoCodec;
+import com.google.devtools.build.lib.starlarkbuildapi.proto.ProtoToolchainInfoApi;
+
+/**
+ * Information about the tools used by the <code>proto_*</code> and <code>LANG_proto_*</code> rules.
+ */
+@Immutable
+@AutoCodec
+public class ProtoToolchainInfo extends ToolchainInfo implements ProtoToolchainInfoApi {
+  @AutoCodec.Instantiator
+  public ProtoToolchainInfo() {
+    super(ImmutableMap.of());
+  }
+}

src/main/java/com/google/devtools/build/lib/rules/proto/ProtoToolchainRule.java

@@ -0,0 +1,40 @@
+// Copyright 2020 The Bazel Authors. All rights reserved.
+//
+// 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 com.google.devtools.build.lib.rules.proto;
+
+import com.google.devtools.build.lib.analysis.BaseRuleClasses;
+import com.google.devtools.build.lib.analysis.RuleDefinition;
+import com.google.devtools.build.lib.analysis.RuleDefinitionEnvironment;
+import com.google.devtools.build.lib.packages.RuleClass;
+
+/** Rule definition of the <code>proto_toolchain</code> rule. */
+public class ProtoToolchainRule implements RuleDefinition {
+  @Override
+  public RuleClass build(RuleClass.Builder builder, final RuleDefinitionEnvironment env) {
+    return builder
+        .requiresConfigurationFragments(ProtoConfiguration.class)
+        .advertiseProvider(ProtoToolchainInfo.class)
+        .build();
+  }
+
+  @Override
+  public Metadata getMetadata() {
+    return RuleDefinition.Metadata.builder()
+        .name("proto_toolchain")
+        .ancestors(BaseRuleClasses.BaseRule.class)
+        .factoryClass(ProtoToolchain.class)
+        .build();
+  }
+}

src/main/java/com/google/devtools/build/lib/starlarkbuildapi/proto/BUILD

@@ -25,6 +25,7 @@ java_library(
         "//src/main/java/com/google/devtools/build/lib/packages/semantics",
         "//src/main/java/com/google/devtools/build/lib/starlarkbuildapi",
         "//src/main/java/com/google/devtools/build/lib/starlarkbuildapi/core",
+        "//src/main/java/com/google/devtools/build/lib/starlarkbuildapi/platform",
         "//src/main/java/net/starlark/java/annot",
         "//src/main/java/net/starlark/java/eval",
         "//third_party:guava",

src/main/java/com/google/devtools/build/lib/starlarkbuildapi/proto/ProtoToolchainInfoApi.java

@@ -0,0 +1,26 @@
+// Copyright 2020 The Bazel Authors. All rights reserved.
+//
+// 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 com.google.devtools.build.lib.starlarkbuildapi.proto;
+
+import com.google.devtools.build.docgen.annot.DocCategory;
+import com.google.devtools.build.lib.starlarkbuildapi.platform.ToolchainInfoApi;
+import net.starlark.java.annot.StarlarkBuiltin;
+
+/** Provides access to information about the Protobuf toolchain rule. */
+@StarlarkBuiltin(
+    name = "ProtoToolchainInfo",
+    category = DocCategory.PROVIDER,
+    doc = "Provides access to information about the Protobuf toolchain rule.")
+public interface ProtoToolchainInfoApi  extends ToolchainInfoApi {}

tools/BUILD

@@ -27,6 +27,7 @@ filegroup(
         "//tools/test:srcs",
         "//tools/test/CoverageOutputGenerator/java/com/google/devtools/coverageoutputgenerator:srcs",
         "//tools/test/CoverageOutputGenerator/javatests/com/google/devtools/coverageoutputgenerator:srcs",
+        "//tools/proto:srcs",
         "//tools/python:srcs",
         "//tools/runfiles:srcs",
         "//tools/sh:srcs",
@@ -56,6 +57,7 @@ filegroup(
         "//tools/def_parser:srcs",
         "//tools/platforms:srcs",
         "//tools/objc:srcs",
+        "//tools/proto:srcs",
         "//tools/python:embedded_tools",
         "//tools/runfiles:embedded_tools",
         "//tools/test:embedded_tools",

tools/proto/BUILD

@@ -0,0 +1,22 @@
+# Copyright 2020 The Bazel Authors. All rights reserved.
+#
+# 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(default_visibility = ["//visibility:public"])
+
+licenses(["notice"])  # Apache 2.0
+
+filegroup(
+    name = "srcs",
+    srcs = glob(["**"]),
+)

tools/proto/BUILD.tools

@@ -0,0 +1,34 @@
+# Copyright 2020 The Bazel Authors. All rights reserved.
+#
+# 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(default_visibility = ["//visibility:public"])
+
+licenses(["notice"])  # Apache 2.0
+
+# The toolchain type used to distinguish proto toolchains.
+toolchain_type(
+    name = "toolchain_type",
+    visibility = ["//visibility:public"],
+)
+
+# buildifier: disable=native-proto
+proto_toolchain(
+    name = "default_toolchain",
+)
+
+toolchain(
+    name = "toolchain",
+    toolchain = ":default_toolchain",
+    toolchain_type = ":toolchain_type",
+)