Create an "WorkspaceConfig" event to report the local Blaze exec_root to BEP, primarily for local consumers.

Going forward, we may add more workspace/output information to the message. For now it just contains the exec_root.

RELNOTES: None
PiperOrigin-RevId: 251459139
diff --git a/src/main/java/com/google/devtools/build/lib/buildeventstream/BuildEventId.java b/src/main/java/com/google/devtools/build/lib/buildeventstream/BuildEventId.java
index 7266d9d..899c224 100644
--- a/src/main/java/com/google/devtools/build/lib/buildeventstream/BuildEventId.java
+++ b/src/main/java/com/google/devtools/build/lib/buildeventstream/BuildEventId.java
@@ -126,6 +126,13 @@
             .build());
   }
 
+  public static BuildEventId workspaceConfigId() {
+    BuildEventStreamProtos.BuildEventId.WorkspaceConfigId workspaceConfigId =
+        BuildEventStreamProtos.BuildEventId.WorkspaceConfigId.getDefaultInstance();
+    return new BuildEventId(
+        BuildEventStreamProtos.BuildEventId.newBuilder().setWorkspace(workspaceConfigId).build());
+  }
+
   public static BuildEventId fetchId(String url) {
     BuildEventStreamProtos.BuildEventId.FetchId fetchId =
         BuildEventStreamProtos.BuildEventId.FetchId.newBuilder().setUrl(url).build();
diff --git a/src/main/java/com/google/devtools/build/lib/buildeventstream/proto/build_event_stream.proto b/src/main/java/com/google/devtools/build/lib/buildeventstream/proto/build_event_stream.proto
index 79f4882..79e1144 100644
--- a/src/main/java/com/google/devtools/build/lib/buildeventstream/proto/build_event_stream.proto
+++ b/src/main/java/com/google/devtools/build/lib/buildeventstream/proto/build_event_stream.proto
@@ -88,6 +88,8 @@
     repeated string pattern = 1;
   }
 
+  message WorkspaceConfigId {}
+
   // Identifier of an event indicating that a target has been expanded by
   // identifying for which configurations it should be build.
   message TargetConfiguredId {
@@ -209,6 +211,7 @@
     BuildFinishedId build_finished = 9;
     BuildToolLogsId build_tool_logs = 20;
     BuildMetricsId build_metrics = 22;
+    WorkspaceConfigId workspace = 23;
   }
 }
 
@@ -303,6 +306,13 @@
   int64 server_pid = 8;
 }
 
+// Configuration related to the blaze workspace and output tree.
+message WorkspaceConfig {
+  // The root of the local blaze exec root. All output files live underneath
+  // this at "blaze-out/".
+  string local_exec_root = 1;
+}
+
 // Payload of an event reporting the command-line of the invocation as
 // originally received by the server. Note that this is not the command-line
 // given by the user, as the client adds information about the invocation,
@@ -698,5 +708,6 @@
     BuildFinished finished = 14;
     BuildToolLogs build_tool_logs = 23;
     BuildMetrics build_metrics = 24;
+    WorkspaceConfig workspace_info = 25;
   }
 }
diff --git a/src/main/java/com/google/devtools/build/lib/runtime/CommandEnvironment.java b/src/main/java/com/google/devtools/build/lib/runtime/CommandEnvironment.java
index 17851c0..eaf0153 100644
--- a/src/main/java/com/google/devtools/build/lib/runtime/CommandEnvironment.java
+++ b/src/main/java/com/google/devtools/build/lib/runtime/CommandEnvironment.java
@@ -427,6 +427,7 @@
   public void setWorkspaceName(String workspaceName) {
     Preconditions.checkState(this.workspaceName == null, "workspace name can only be set once");
     this.workspaceName = workspaceName;
+    eventBus.post(new ExecRootEvent(getExecRoot()));
   }
   /**
    * Returns if the client passed a valid workspace to be used for the build.
diff --git a/src/main/java/com/google/devtools/build/lib/runtime/ExecRootEvent.java b/src/main/java/com/google/devtools/build/lib/runtime/ExecRootEvent.java
new file mode 100644
index 0000000..d6588bb
--- /dev/null
+++ b/src/main/java/com/google/devtools/build/lib/runtime/ExecRootEvent.java
@@ -0,0 +1,55 @@
+// 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.runtime;
+
+import com.google.common.collect.ImmutableList;
+import com.google.devtools.build.lib.buildeventstream.BuildEvent;
+import com.google.devtools.build.lib.buildeventstream.BuildEventContext;
+import com.google.devtools.build.lib.buildeventstream.BuildEventId;
+import com.google.devtools.build.lib.buildeventstream.BuildEventStreamProtos;
+import com.google.devtools.build.lib.vfs.Path;
+import java.util.Collection;
+
+/** An event that receives the execRoot of this blaze invocation. */
+public class ExecRootEvent implements BuildEvent {
+
+  private final Path execRoot;
+
+  public ExecRootEvent(Path execRoot) {
+    this.execRoot = execRoot;
+  }
+
+  @Override
+  public BuildEventStreamProtos.BuildEvent asStreamProto(BuildEventContext context) {
+    BuildEventStreamProtos.WorkspaceConfig workspaceConfigEvent =
+        BuildEventStreamProtos.WorkspaceConfig.newBuilder()
+            .setLocalExecRoot(execRoot.getPathString())
+            .build();
+    return BuildEventStreamProtos.BuildEvent.newBuilder()
+        .setId(getEventId().asStreamProto())
+        .setWorkspaceInfo(workspaceConfigEvent)
+        .build();
+  }
+
+  @Override
+  public BuildEventId getEventId() {
+    return BuildEventId.workspaceConfigId();
+  }
+
+  @Override
+  public Collection<BuildEventId> getChildrenEvents() {
+    return ImmutableList.of();
+  }
+}