1 files changed, 58 insertions, 0 deletions
diff --git a/src/main/java/com/google/devtools/build/lib/query2/engine/QueryException.java b/src/main/java/com/google/devtools/build/lib/query2/engine/QueryException.java
new file mode 100644
index 0000000000..71c1a8a8a6
--- /dev/null
+++ b/src/main/java/com/google/devtools/build/lib/query2/engine/QueryException.java
@@ -0,0 +1,58 @@
+// 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.engine;
+
+/**
+ */
+public class QueryException extends Exception {
+
+  /**
+   * Returns a better error message for the query.
+   */
+  static String describeFailedQuery(QueryException e, QueryExpression toplevel) {
+    QueryExpression badQuery = e.getFailedExpression();
+    if (badQuery == null) {
+      return "Evaluation failed: " + e.getMessage();
+    }
+    return badQuery == toplevel
+        ? "Evaluation of query \"" + toplevel + "\" failed: " + e.getMessage()
+        : "Evaluation of subquery \"" + badQuery
+            + "\" failed (did you want to use --keep_going?): " + e.getMessage();
+  }
+
+  private final QueryExpression expression;
+
+  public QueryException(QueryException e, QueryExpression toplevel) {
+    super(describeFailedQuery(e, toplevel), e);
+    this.expression = null;
+  }
+
+  public QueryException(QueryExpression expression, String message) {
+    super(message);
+    this.expression = expression;
+  }
+
+  public QueryException(String message) {
+    this(null, message);
+  }
+
+  /**
+   * Returns the subexpression for which evaluation failed, or null if
+   * the failure occurred during lexing/parsing.
+   */
+  public QueryExpression getFailedExpression() {
+    return expression;
+  }
+
+}