Add bazel help builtin-symbols-as-proto

RELNOTES: The new `bazel help builtin-symbols-as-proto` subcommand emits a base64-encoded proto message describing the built-in Starlark types and global symbols. See `src/main/protobuf/builtin.proto` for the message definition.

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

@@ -213,13 +213,21 @@ java_library(
     ],
 )
 
+java_library(
+    name = "builtin_symbols_proto",
+    resources = [
+        "//src/main/java/com/google/devtools/build/lib:gen_api_proto",
+    ],
+)
+
 java_binary(
     name = "BazelServer",
     javacopts = [
         "-Xlint:all",
     ],
     main_class = "com.google.devtools.build.lib.bazel.Bazel",
     runtime_deps = [
+        ":builtin_symbols_proto",  # Adding this to :main would create a cycle
         ":main",
         "//src/main/java/com/google/devtools/build/lib/server",
         "//src/main/java/com/google/devtools/build/lib/util:simple_log_handler",  # See startup_options.cc

src/main/java/com/google/devtools/build/lib/runtime/commands/HelpCommand.java

@@ -27,6 +27,7 @@
 import com.google.devtools.build.lib.analysis.ConfiguredRuleClassProvider;
 import com.google.devtools.build.lib.analysis.NoBuildEvent;
 import com.google.devtools.build.lib.events.Event;
+import com.google.devtools.build.lib.events.Reporter;
 import com.google.devtools.build.lib.runtime.BlazeCommand;
 import com.google.devtools.build.lib.runtime.BlazeCommandResult;
 import com.google.devtools.build.lib.runtime.BlazeCommandUtils;
@@ -52,6 +53,8 @@
 import com.google.devtools.common.options.OptionsParser;
 import com.google.devtools.common.options.OptionsParser.HelpVerbosity;
 import com.google.devtools.common.options.OptionsParsingResult;
+import java.io.BufferedInputStream;
+import java.io.IOException;
 import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.Base64;
@@ -155,6 +158,8 @@ public BlazeCommandResult exec(CommandEnvironment env, OptionsParsingResult opti
       case "flags-as-proto":
         emitFlagsAsProtoHelp(runtime, outErr);
         return BlazeCommandResult.success();
+      case "builtin-symbols-as-proto":
+        return emitBuiltinSymbolsAsProtoHelp(env.getReporter(), outErr);
       case "everything-as-html":
         new HtmlEmitter(runtime).emit(outErr);
         return BlazeCommandResult.success();
@@ -263,6 +268,29 @@ private static void emitFlagsAsProtoHelp(BlazeRuntime runtime, OutErr outErr) {
     outErr.printOut(Base64.getEncoder().encodeToString(collectionBuilder.build().toByteArray()));
   }
 
+  private BlazeCommandResult emitBuiltinSymbolsAsProtoHelp(Reporter reporter, OutErr outErr) {
+    try {
+      byte[] builtinsProtoBytes;
+      try (var in =
+          HelpCommand.class
+              .getClassLoader()
+              .getResourceAsStream("com/google/devtools/build/lib/builtin.pb")) {
+        if (in == null) {
+          throw new IOException("Could not find built-in symbols proto file");
+        }
+        try (var bufferedIn = new BufferedInputStream(in)) {
+          builtinsProtoBytes = bufferedIn.readAllBytes();
+        }
+      }
+      outErr.printOut(Base64.getEncoder().encodeToString(builtinsProtoBytes));
+    } catch (IOException e) {
+      String message = "Failed to get built-in symbols proto: " + e.getMessage();
+      reporter.handle(Event.error(null, message));
+      return createFailureResult(message, Code.COMMAND_NOT_FOUND);
+    }
+    return BlazeCommandResult.success();
+  }
+
   private static BazelFlagsProto.FlagInfo.Builder createFlagInfo(OptionDefinition option) {
     BazelFlagsProto.FlagInfo.Builder flagBuilder = BazelFlagsProto.FlagInfo.newBuilder();
     flagBuilder.setName(option.getOptionName());

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

@@ -16,6 +16,7 @@ java_library(
         exclude = [
             "commands/ConfigCommandTest.java",
             "commands/DumpCommandTest.java",
+            "commands/HelpCommandTest.java",
         ],
     ),
     deps = [
@@ -161,6 +162,23 @@ java_test(
     ],
 )
 
+java_test(
+    name = "HelpCommandTest",
+    srcs = ["commands/HelpCommandTest.java"],
+    deps = [
+        "//src/main/java/com/google/devtools/build/lib:runtime",
+        "//src/main/java/com/google/devtools/build/lib:runtime/blaze_command_result",
+        "//src/main/java/com/google/devtools/build/lib/bazel:builtin_symbols_proto",
+        "//src/main/java/com/google/devtools/build/lib/runtime/commands",
+        "//src/main/java/com/google/devtools/build/lib/util/io:out-err",
+        "//src/main/protobuf:builtin_java_proto",
+        "//src/test/java/com/google/devtools/build/lib/buildtool/util",
+        "//third_party:guava",
+        "//third_party:junit4",
+        "//third_party:truth",
+    ],
+)
+
 java_test(
     name = "RuntimeTests",
     test_class = "com.google.devtools.build.lib.AllTests",

src/test/java/com/google/devtools/build/lib/runtime/commands/HelpCommandTest.java

@@ -0,0 +1,77 @@
+// Copyright 2022 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.runtime.commands;
+
+import static com.google.common.truth.Truth.assertThat;
+import static java.util.stream.Collectors.toMap;
+
+import com.google.common.collect.Lists;
+import com.google.devtools.build.docgen.builtin.BuiltinProtos;
+import com.google.devtools.build.lib.buildtool.util.BuildIntegrationTestCase;
+import com.google.devtools.build.lib.runtime.BlazeCommandDispatcher;
+import com.google.devtools.build.lib.runtime.BlazeCommandResult;
+import com.google.devtools.build.lib.runtime.BlazeRuntime;
+import com.google.devtools.build.lib.util.io.RecordingOutErr;
+import java.util.Base64;
+import java.util.Collections;
+import java.util.List;
+import org.junit.Before;
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.junit.runners.JUnit4;
+
+/** Tests for {@link HelpCommand}. */
+@RunWith(JUnit4.class)
+public final class HelpCommandTest extends BuildIntegrationTestCase {
+  private BlazeCommandDispatcher dispatcher;
+  private RecordingOutErr recordingOutErr;
+
+  @Before
+  public void createDispatcher() {
+    BlazeRuntime runtime = getRuntime();
+    runtime.getCommandMap().put("help", new HelpCommand());
+    dispatcher = new BlazeCommandDispatcher(runtime);
+  }
+
+  @Before
+  public void createRecording() {
+    recordingOutErr = new RecordingOutErr();
+  }
+
+  private BlazeCommandResult help(String... args) throws InterruptedException {
+    List<String> params = Lists.newArrayList("help");
+    Collections.addAll(params, args);
+    return dispatcher.exec(params, "test", recordingOutErr);
+  }
+
+  @Test
+  public void wellKnownCallablesInBuiltinSymbolsProto() throws Exception {
+    assertThat(help("builtin-symbols-as-proto").isSuccess()).isTrue();
+    assertThat(recordingOutErr.errAsLatin1()).isEmpty();
+    String base64Proto = recordingOutErr.outAsLatin1();
+    byte[] rawProto = Base64.getDecoder().decode(base64Proto);
+    var builtins = BuiltinProtos.Builtins.parseFrom(rawProto);
+
+    assertThat(
+            builtins.getGlobalList().stream()
+                .filter(BuiltinProtos.Value::hasCallable)
+                .filter(global -> !global.getCallable().getParamList().isEmpty())
+                .collect(toMap(BuiltinProtos.Value::getName, BuiltinProtos.Value::getApiContext)))
+        .containsAtLeast(
+            "range", BuiltinProtos.ApiContext.ALL,
+            "glob", BuiltinProtos.ApiContext.BUILD,
+            "DefaultInfo", BuiltinProtos.ApiContext.BZL);
+  }
+}