Expose proto fragment fields necessary for writing proto_toolchain to Starlark

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

@@ -982,6 +982,7 @@ java_library(
         ":util",
         "//src/main/java/com/google/devtools/build/lib/actions",
         "//src/main/java/com/google/devtools/build/lib/actions:commandline_item",
+        "//src/main/java/com/google/devtools/build/lib/analysis/skylark/annotations",
         "//src/main/java/com/google/devtools/build/lib/collect/nestedset",
         "//src/main/java/com/google/devtools/build/lib/concurrent",
         "//src/main/java/com/google/devtools/build/lib/skyframe/serialization/autocodec",

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

@@ -14,6 +14,7 @@
 
 package com.google.devtools.build.lib.rules.proto;
 
+import com.google.common.base.Preconditions;
 import com.google.common.collect.ImmutableList;
 import com.google.common.collect.ImmutableSet;
 import com.google.devtools.build.lib.analysis.config.BuildConfiguration.Fragment;
@@ -23,6 +24,7 @@
 import com.google.devtools.build.lib.analysis.config.CoreOptionConverters.StrictDepsMode;
 import com.google.devtools.build.lib.analysis.config.FragmentOptions;
 import com.google.devtools.build.lib.analysis.config.InvalidConfigurationException;
+import com.google.devtools.build.lib.analysis.skylark.annotations.SkylarkConfigurationField;
 import com.google.devtools.build.lib.cmdline.Label;
 import com.google.devtools.build.lib.concurrent.ThreadSafety.Immutable;
 import com.google.devtools.build.lib.skylarkbuildapi.ProtoConfigurationApi;
@@ -230,6 +232,7 @@ private ProtoConfiguration(Options options) {
     this.options = options;
   }
 
+  @Override
   public ImmutableList<String> protocOpts() {
     return protocOpts;
   }
@@ -243,6 +246,20 @@ public boolean runExperimentalProtoExtraActions() {
     return options.experimentalProtoExtraActions;
   }
 
+  @SkylarkConfigurationField(
+      // Must match the value of `_protoc_key`
+      // in `@rules_proto//proto/private/rules:proto_toolchain.bzl`.
+      name = "protoc_do_not_use_or_we_will_break_you_without_mercy",
+      doc = "Exposes the value of `--proto_compiler`."
+                + "<p><b>Do not use this field directly</b>, its only purpose is to help with "
+                + "migration of Protobuf rules to Starlark.</p>"
+                + "<p>Instead, you can access the value through proto_toolchain</p>"
+                + "<p><pre class=\"language-python\">\n"
+                + "def _my_rule_impl(ctx):"
+                + "    proto_toolchain = ctx.toolchains[\"@rules_proto//proto:toolchain\"]\n"
+                + "    protoc = proto_toolchain.compiler\n"
+                + "</pre></p>"
+  )
   public Label protoCompiler() {
     return options.protoCompiler;
   }
@@ -267,6 +284,23 @@ public StrictDepsMode strictProtoDeps() {
     return options.strictProtoDeps;
   }
 
+  @Override
+  public String starlarkStrictDeps() {
+    switch (strictProtoDeps()) {
+      case OFF:  // fall-through
+      case DEFAULT:
+        return "OFF";
+
+      case WARN:
+        return "WARN";
+
+      case ERROR:  // fall-through
+      case STRICT:
+        return "ERROR";
+    }
+    throw new IllegalStateException();
+  }
+
   public List<String> ccProtoLibraryHeaderSuffixes() {
     return ccProtoLibraryHeaderSuffixes;
   }

src/main/java/com/google/devtools/build/lib/skylarkbuildapi/ProtoConfigurationApi.java

@@ -14,6 +14,8 @@
 
 package com.google.devtools.build.lib.skylarkbuildapi;
 
+import com.google.common.collect.ImmutableList;
+import com.google.devtools.build.lib.skylarkinterface.SkylarkCallable;
 import com.google.devtools.build.lib.skylarkinterface.SkylarkModule;
 import com.google.devtools.build.lib.skylarkinterface.SkylarkModuleCategory;
 import com.google.devtools.build.lib.syntax.StarlarkValue;
@@ -22,5 +24,65 @@
 @SkylarkModule(
     name = "proto",
     category = SkylarkModuleCategory.CONFIGURATION_FRAGMENT,
-    doc = "A configuration fragment representing protocol buffers.")
-public interface ProtoConfigurationApi extends StarlarkValue {}
+    doc = "A configuration fragment representing protocol buffers. "
+              + "<p><b>Do not use these fields directly<b>, they are considered an implementation "
+              + "detail and will be removed after migrating Protobuf rules to Starlark.</p>"
+              // TODO(yannic): Link to generated docs of `proto_toolchain`.
+              // https://github.com/bazelbuild/bazel/issues/9203
+              + "<p>Instead, you can access them through proto_toolchain</p>"
+              + "<p><pre class=\"language-python\">\n"
+              + "def _my_rule_impl(ctx):\n"
+              + "    proto_toolchain = ctx.toolchains[\"@rules_proto//proto:toolchain\"]\n"
+              + "\n"
+              + "    # Contains the protoc binary, as specified by `--proto_compiler`.\n"
+              + "    protoc = proto_toolchain.compiler\n"
+              + "\n"
+              + "    # Contains extra args to pass to protoc, as specified by `--protocopt`.\n"
+              + "    compiler_options = proto_toolchain.compiler_options\n"
+              + "\n"
+              + "    # Contains the strict-dependency mode to use for Protocol Buffers\n"
+              + "    # (i.e. 'OFF`, `WARN`, `ERROR`), as specified by `--strict_proto_deps`.\n"
+              + "    strict_deps = proto_toolchain.strict_deps\n"
+              + "\n"
+              + "my_rule = rule(\n"
+              + "    implementation = _my_rule_impl,\n"
+              + "    attrs = {},\n"
+              + "    toolchains = [\n"
+              + "        \"@rules_proto//proto:toolchain\",\n"
+              + "    ],\n"
+              + ")\n"
+              + "</pre></p>"
+)
+public interface ProtoConfigurationApi extends StarlarkValue {
+  @SkylarkCallable(
+      // Must match the value of `_protocopt_key`
+      // in `@rules_proto//proto/private/rules:proto_toolchain.bzl`.
+      name = "protocopt_do_not_use_or_we_will_break_you_without_mercy",
+      doc = "Exposes the value of `--protocopt`."
+                + "<p><b>Do not use this field directly</b>, its only purpose is to help with "
+                + "migration of Protobuf rules to Starlark.</p>"
+                + "<p>Instead, you can access the value through proto_toolchain</p>"
+                + "<p><pre class=\"language-python\">\n"
+                + "def _my_rule_impl(ctx):"
+                + "    proto_toolchain = ctx.toolchains[\"@rules_proto//proto:toolchain\"]\n"
+                + "    compiler_options = proto_toolchain.compiler_options\n"
+                + "</pre></p>",
+      structField = true)
+  ImmutableList<String> protocOpts();
+
+  @SkylarkCallable(
+      // Must match the value of `_strict_deps_key`
+      // in `@rules_proto//proto/private/rules:proto_toolchain.bzl`.
+      name = "strict_deps_do_not_use_or_we_will_break_you_without_mercy",
+      doc = "Exposes the value of `--strict_proto_deps`."
+                + "<p><b>Do not use this field directly</b>, its only purpose is to help with "
+                + "migration of Protobuf rules to Starlark.</p>"
+                + "<p>Instead, you can access the value through proto_toolchain</p>"
+                + "<p><pre class=\"language-python\">\n"
+                + "def _my_rule_impl(ctx):"
+                + "    proto_toolchain = ctx.toolchains[\"@rules_proto//proto:toolchain\"]\n"
+                + "    strict_deps = proto_toolchain.strict_deps\n"
+                + "</pre></p>",
+      structField = true)
+  String starlarkStrictDeps();
+}

src/main/java/com/google/devtools/build/lib/skylarkbuildapi/proto/ProtoModuleApi.java

@@ -14,6 +14,7 @@
 
 package com.google.devtools.build.lib.skylarkbuildapi.proto;
 
+import com.google.devtools.build.lib.skylarkinterface.SkylarkCallable;
 import com.google.devtools.build.lib.skylarkinterface.SkylarkModule;
 import com.google.devtools.build.lib.syntax.StarlarkValue;
 
@@ -31,4 +32,12 @@
             + "to load this symbol from <a href=\"https://github.com/bazelbuild/rules_proto\">"
             + "rules_proto</a>"
             + "</p>")
-public interface ProtoModuleApi extends StarlarkValue {}
+public interface ProtoModuleApi extends StarlarkValue {
+  @Deprecated
+  @SkylarkCallable(
+      name = "has_protoc_do_not_use_or_we_will_break_you_without_mercy",
+      doc = "Do not use this field, its only purpose is to help with migration of "
+                + "Protobuf rules to Starlark.",
+      structField = true)
+  default void configurationFieldProtocExists() {}
+}

src/test/java/com/google/devtools/build/lib/BUILD

@@ -1421,6 +1421,17 @@ java_test(
     ],
 )
 
+java_test(
+    name = "ProtoConfigurationTest",
+    srcs = ["rules/proto/ProtoConfigurationTest.java"],
+    deps = [
+        ":actions_testutil",
+        ":analysis_testutil",
+        ":guava_junit_truth",
+        "//src/main/java/com/google/devtools/build/lib/actions",
+    ],
+)
+
 java_test(
     name = "BazelProtoLibraryTest",
     srcs = ["rules/proto/BazelProtoLibraryTest.java"],

src/test/java/com/google/devtools/build/lib/rules/proto/ProtoConfigurationTest.java

@@ -0,0 +1,129 @@
+// Copyright 2019 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 static com.google.common.truth.Truth.assertThat;
+import static com.google.devtools.build.lib.actions.util.ActionsTestUtil.getFirstArtifactEndingWith;
+
+import com.google.devtools.build.lib.actions.Artifact;
+import com.google.devtools.build.lib.analysis.util.BuildViewTestCase;
+import org.junit.Before;
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.junit.runners.JUnit4;
+
+@RunWith(JUnit4.class)
+public class ProtoConfigurationTest extends BuildViewTestCase {
+  @Before
+  public void setUp() throws Exception {
+    scratch.file("proto/BUILD", "cc_binary(name='compiler')");
+    scratch.file(
+        "proto/defs.bzl",
+        "def check_proto_common():",
+        "    if not hasattr(proto_common,",
+        "                   'has_protoc_do_not_use_or_we_will_break_you_without_mercy'):",
+        "        fail('missing has_protoc_... attribute on proto_common')",
+        "check_proto_common()",
+        "",
+        "def _echo_protocopt_impl(ctx):",
+        "    opts = ctx.fragments.proto.protocopt_do_not_use_or_we_will_break_you_without_mercy",
+        "    f = ctx.actions.declare_file(ctx.attr.name)",
+        "    ctx.actions.run(executable='echo',outputs=[f], arguments=opts)",
+        "    return [DefaultInfo(files=depset([f]))]",
+        "echo_protocopt = rule(_echo_protocopt_impl, fragments=['proto'])",
+        "",
+        "def _echo_strict_deps_impl(ctx):",
+        "    s = ctx.fragments.proto.strict_deps_do_not_use_or_we_will_break_you_without_mercy",
+        "    f = ctx.actions.declare_file(ctx.attr.name)",
+        "    ctx.actions.run(executable='echo',outputs=[f], arguments=[s])",
+        "    return [DefaultInfo(files=depset([f]))]",
+        "echo_strict_deps = rule(_echo_strict_deps_impl, fragments=['proto'])",
+        "",
+        "def _echo_proto_compiler_impl(ctx):",
+        "    return [DefaultInfo(files=depset([ctx.executable._compiler]))]",
+        "_protoc_key = 'protoc_do_not_use_or_we_will_break_you_without_mercy'",
+        "echo_proto_compiler = rule(",
+        "    implementation = _echo_proto_compiler_impl,",
+        "    attrs = {",
+        "        '_compiler': attr.label(",
+        "            executable = True,",
+        "            cfg = 'host',",
+        "            default = configuration_field('proto', _protoc_key),",
+        "        ),",
+        "    },",
+        "    fragments=['proto']",
+        ")");
+  }
+
+  private Artifact getArtifact(String target, String file) throws Exception {
+    return getFirstArtifactEndingWith(getFilesToBuild(getConfiguredTarget(target)), file);
+  }
+
+  @Test
+  public void readProtocopt() throws Exception {
+    scratch.file(
+        "x/BUILD",
+        "load('//proto:defs.bzl', 'echo_protocopt')",
+        "echo_protocopt(name = 'x')");
+    assertThat(getGeneratingSpawnAction(getArtifact("//x", "x")).getRemainingArguments())
+        .isEmpty();
+
+    useConfiguration("--protocopt=--foo", "--protocopt=--bar=10");
+    assertThat(getGeneratingSpawnAction(getArtifact("//x", "x")).getRemainingArguments())
+        .containsExactly("--foo", "--bar=10");
+  }
+
+  @Test
+  public void readStrictDeps() throws Exception {
+    scratch.file(
+        "x/BUILD",
+        "load('//proto:defs.bzl', 'echo_strict_deps')",
+        "echo_strict_deps(name = 'x')");
+    assertThat(getGeneratingSpawnAction(getArtifact("//x", "x")).getRemainingArguments())
+        .containsExactly("ERROR");
+
+    useConfiguration("--strict_proto_deps=OFF");
+    assertThat(getGeneratingSpawnAction(getArtifact("//x", "x")).getRemainingArguments())
+        .containsExactly("OFF");
+
+    useConfiguration("--strict_proto_deps=DEFAULT");
+    assertThat(getGeneratingSpawnAction(getArtifact("//x", "x")).getRemainingArguments())
+        .containsExactly("OFF");
+
+    useConfiguration("--strict_proto_deps=WARN");
+    assertThat(getGeneratingSpawnAction(getArtifact("//x", "x")).getRemainingArguments())
+        .containsExactly("WARN");
+
+    useConfiguration("--strict_proto_deps=ERROR");
+    assertThat(getGeneratingSpawnAction(getArtifact("//x", "x")).getRemainingArguments())
+        .containsExactly("ERROR");
+
+    useConfiguration("--strict_proto_deps=DEFAULT");
+    assertThat(getGeneratingSpawnAction(getArtifact("//x", "x")).getRemainingArguments())
+        .containsExactly("OFF");
+  }
+
+  @Test
+  public void readProtoCompiler() throws Exception {
+    scratch.file(
+        "x/BUILD",
+        "load('//proto:defs.bzl', 'echo_proto_compiler')",
+        "echo_proto_compiler(name = 'x')");
+
+    useConfiguration("--proto_compiler=//proto:compiler");
+    assertThat(getArtifact("//x", "compiler").getRootRelativePathString())
+        .startsWith("proto/compiler");  // Ends with `.exe` on Windows.
+  }
+}