1 files changed, 143 insertions, 0 deletions
diff --git a/src/main/java/com/google/devtools/build/lib/runtime/EventHandlerPreconditions.java b/src/main/java/com/google/devtools/build/lib/runtime/EventHandlerPreconditions.java
new file mode 100644
index 0000000000..f4ef8e3f22
--- /dev/null
+++ b/src/main/java/com/google/devtools/build/lib/runtime/EventHandlerPreconditions.java
@@ -0,0 +1,143 @@
+// Copyright 2014 Google Inc. 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.base.Preconditions;
+import com.google.devtools.build.lib.events.ExceptionListener;
+import com.google.devtools.build.lib.util.LoggingUtil;
+
+import java.util.logging.Level;
+
+/**
+ * Reports precondition failures from within an event handler.
+ * Necessary because the EventBus silently ignores exceptions thrown from within a handler.
+ * This class logs the exceptions and creates some noise when a precondition check fails.
+ */
+public class EventHandlerPreconditions {
+
+  private final ExceptionListener listener;
+
+  /**
+   * Creates a new precondition helper which outputs errors to the given reporter.
+   */
+  public EventHandlerPreconditions(ExceptionListener listener) {
+    this.listener = listener;
+  }
+
+  /**
+   * Verifies that the given condition (a check on an argument) is true,
+   * throwing an IllegalArgumentException if not.
+   *
+   * @param condition a condition to check for truth.
+   * @throws IllegalArgumentException if the condition is false.
+   */
+  @SuppressWarnings("unused")
+  public void checkArgument(boolean condition) {
+    checkArgument(condition, null);
+  }
+
+  /**
+   * Verifies that the given condition (a check on an argument) is true,
+   * throwing an IllegalArgumentException with the given message if not.
+   *
+   * @param condition a condition to check for truth.
+   * @param message extra information to output if the condition is false.
+   * @throws IllegalArgumentException if the condition is false.
+   */
+  public void checkArgument(boolean condition, String message) {
+    try {
+      Preconditions.checkArgument(condition, message);
+    } catch (IllegalArgumentException iae) {
+      String error = "Event handler argument check failed";
+      LoggingUtil.logToRemote(Level.SEVERE, error, iae);
+      listener.error(null, error, iae);
+      throw iae; // Still terminate the handler.
+    }
+  }
+
+  /**
+   * Verifies that the given condition (a check against the program's current state) is true,
+   * throwing an IllegalStateException if not.
+   *
+   * @param condition a condition to check for truth.
+   * @throws IllegalStateException if the condition is false.
+   */
+  public void checkState(boolean condition) {
+    checkState(condition, null);
+  }
+
+  /**
+   * Verifies that the given condition (a check against the program's current state) is true,
+   * throwing an IllegalStateException with the given message if not.
+   *
+   * @param condition a condition to check for truth.
+   * @param message extra information to output if the condition is false.
+   * @throws IllegalStateException if the condition is false.
+   */
+  public void checkState(boolean condition, String message) {
+    try {
+      Preconditions.checkState(condition, message);
+    } catch (IllegalStateException ise) {
+      String error = "Event handler state check failed";
+      LoggingUtil.logToRemote(Level.SEVERE, error, ise);
+      listener.error(null, error, ise);
+      throw ise; // Still terminate the handler.
+    }
+  }
+
+  /**
+   * Fails with an IllegalStateException when invoked.
+   */
+  public void fail(String message) {
+    String error = "Event handler failed: " + message;
+    IllegalStateException ise = new IllegalStateException(message);
+    LoggingUtil.logToRemote(Level.SEVERE, error, ise);
+    listener.error(null, error, ise);
+    throw ise;
+  }
+
+  /**
+   * Verifies that the given argument is not null, throwing a NullPointerException if it is null.
+   * Returns the original argument or throws.
+   *
+   * @param object an object to test for null.
+   * @return the reference which was checked.
+   * @throws NullPointerException if the object is null.
+   */
+  public <T> T checkNotNull(T object) {
+    return checkNotNull(object, null);
+  }
+
+  /**
+   * Verifies that the given argument is not null, throwing a
+   * NullPointerException with the given message if it is null.
+   * Returns the original argument or throws.
+   *
+   * @param object an object to test for null.
+   * @param message extra information to output if the object is null.
+   * @return the reference which was checked.
+   * @throws NullPointerException if the object is null.
+   */
+  public <T> T checkNotNull(T object, String message) {
+    try {
+      return Preconditions.checkNotNull(object, message);
+    } catch (NullPointerException npe) {
+      String error = "Event handler not-null check failed";
+      LoggingUtil.logToRemote(Level.SEVERE, error, npe);
+      listener.error(null, error, npe);
+      throw npe;
+    }
+  }
+}