1 files changed, 53 insertions, 0 deletions
diff --git a/src/main/java/com/google/devtools/build/lib/query2/ErrorPrintingTargetEdgeErrorObserver.java b/src/main/java/com/google/devtools/build/lib/query2/ErrorPrintingTargetEdgeErrorObserver.java
new file mode 100644
index 0000000000..d47b8f3b4f
--- /dev/null
+++ b/src/main/java/com/google/devtools/build/lib/query2/ErrorPrintingTargetEdgeErrorObserver.java
@@ -0,0 +1,53 @@
+// 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.query2;
+
+import com.google.devtools.build.lib.concurrent.ThreadSafety;
+import com.google.devtools.build.lib.events.Event;
+import com.google.devtools.build.lib.events.EventHandler;
+import com.google.devtools.build.lib.packages.NoSuchThingException;
+import com.google.devtools.build.lib.packages.Target;
+import com.google.devtools.build.lib.packages.TargetUtils;
+import com.google.devtools.build.lib.syntax.Label;
+
+/**
+ * Record errors, such as missing package/target or rules containing errors,
+ * encountered during visitation. Emit an error message upon encountering
+ * missing edges
+ *
+ * The accessor {@link #hasErrors}) may not be called until the concurrent phase
+ * is over, i.e. all external calls to visit() methods have completed.
+ */
+@ThreadSafety.ConditionallyThreadSafe // condition: only call hasErrors
+                                      // once the visitation is complete.
+class ErrorPrintingTargetEdgeErrorObserver extends TargetEdgeErrorObserver {
+
+  private final EventHandler eventHandler;
+
+  /**
+   * @param eventHandler eventHandler to route exceptions to as errors.
+   */
+  public ErrorPrintingTargetEdgeErrorObserver(EventHandler eventHandler) {
+    this.eventHandler = eventHandler;
+  }
+
+  @ThreadSafety.ThreadSafe
+  @Override
+  public void missingEdge(Target target, Label label, NoSuchThingException e) {
+    eventHandler.handle(Event.error(TargetUtils.getLocationMaybe(target),
+        TargetUtils.formatMissingEdge(target, label, e)));
+    super.missingEdge(target, label, e);
+  }
+}