Add an option to enable an experimental UI

By enabling this option (default is off), a new, still experimental
UI will be used. As it is developped from scratch, this commit simply
implements a UI that does not produce any output at all.

--
Change-Id: I895c0e0744c008212efc7bdfca1457f7907c9b64
Reviewed-on: https://bazel-review.googlesource.com/#/c/3009/
MOS_MIGRATED_REVID=115441032

3 files changed, 65 insertions, 2 deletions

diff --git a/src/main/java/com/google/devtools/build/lib/runtime/BlazeCommandDispatcher.java b/src/main/java/com/google/devtools/build/lib/runtime/BlazeCommandDispatcher.java
index 8daee39a0a..262c796db9 100644
--- a/src/main/java/com/google/devtools/build/lib/runtime/BlazeCommandDispatcher.java
+++ b/src/main/java/com/google/devtools/build/lib/runtime/BlazeCommandDispatcher.java
@@ -624,7 +624,10 @@ public class BlazeCommandDispatcher {
   private EventHandler createEventHandler(OutErr outErr,
       BlazeCommandEventHandler.Options eventOptions) {
     EventHandler eventHandler;
-    if ((eventOptions.useColor() || eventOptions.useCursorControl())) {
+    if (eventOptions.experimentalUi) {
+      // The experimental event handler is not to be rate limited.
+      return new ExperimentalEventHandler(outErr, eventOptions);
+    } else if ((eventOptions.useColor() || eventOptions.useCursorControl())) {
       eventHandler = new FancyTerminalEventHandler(outErr, eventOptions);
     } else {
       eventHandler = new BlazeCommandEventHandler(outErr, eventOptions);
@@ -640,7 +643,10 @@ public class BlazeCommandDispatcher {
     if (eventHandler instanceof FancyTerminalEventHandler) {
       // Make sure that the terminal state of the old event handler is clear
       // before creating a new one.
-      ((FancyTerminalEventHandler)eventHandler).resetTerminal();
+      ((FancyTerminalEventHandler) eventHandler).resetTerminal();
+    }
+    if (eventHandler instanceof ExperimentalEventHandler) {
+      ((ExperimentalEventHandler) eventHandler).resetTerminal();
     }
   }
 
diff --git a/src/main/java/com/google/devtools/build/lib/runtime/BlazeCommandEventHandler.java b/src/main/java/com/google/devtools/build/lib/runtime/BlazeCommandEventHandler.java
index 9aadac8bb8..11f3e8e627 100644
--- a/src/main/java/com/google/devtools/build/lib/runtime/BlazeCommandEventHandler.java
+++ b/src/main/java/com/google/devtools/build/lib/runtime/BlazeCommandEventHandler.java
@@ -141,6 +141,14 @@ public class BlazeCommandEventHandler implements EventHandler {
         help = "Forces --experimental_external_repositories.")
     public boolean forceExternalRepositories;
 
+    @Option(
+      name = "experimental_ui",
+      defaultValue = "false",
+      category = "hidden",
+      help = "Enable the experimental new Bazel UI."
+    )
+    public boolean experimentalUi;
+
     public boolean useColor() {
       return useColorEnum == UseColor.YES || (useColorEnum == UseColor.AUTO && isATty);
     }
diff --git a/src/main/java/com/google/devtools/build/lib/runtime/ExperimentalEventHandler.java b/src/main/java/com/google/devtools/build/lib/runtime/ExperimentalEventHandler.java
new file mode 100644
index 0000000000..b81fddb4ae
--- /dev/null
+++ b/src/main/java/com/google/devtools/build/lib/runtime/ExperimentalEventHandler.java
@@ -0,0 +1,49 @@
+// Copyright 2015 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.devtools.build.lib.events.Event;
+import com.google.devtools.build.lib.util.io.AnsiTerminal;
+import com.google.devtools.build.lib.util.io.OutErr;
+
+import java.io.IOException;
+import java.util.logging.Logger;
+
+/**
+ * An experimental new output stream.
+ */
+public class ExperimentalEventHandler extends BlazeCommandEventHandler {
+  private static Logger LOG = Logger.getLogger(ExperimentalEventHandler.class.getName());
+
+  private final AnsiTerminal terminal;
+
+  public final int terminalWidth;
+
+  public ExperimentalEventHandler(OutErr outErr, BlazeCommandEventHandler.Options options) {
+    super(outErr, options);
+    this.terminal = new AnsiTerminal(outErr.getErrorStream());
+    this.terminalWidth = (options.terminalColumns > 0 ? options.terminalColumns : 80);
+  }
+
+  @Override
+  public void handle(Event event) {}
+
+  public void resetTerminal() {
+    try {
+      terminal.resetTerminal();
+    } catch (IOException e) {
+      LOG.warning("IO Error writing to user terminal: " + e);
+    }
+  }
+}