1 files changed, 30 insertions, 0 deletions
diff --git a/src/main/java/com/google/devtools/build/lib/packages/PredicateWithMessage.java b/src/main/java/com/google/devtools/build/lib/packages/PredicateWithMessage.java
new file mode 100644
index 0000000000..4316f02992
--- /dev/null
+++ b/src/main/java/com/google/devtools/build/lib/packages/PredicateWithMessage.java
@@ -0,0 +1,30 @@
+// 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.packages;
+
+import com.google.common.base.Predicate;
+
+/**
+ * A predicate which supports error messages.
+ * @param <T> - the predicate is applied on T objects
+ */
+public interface PredicateWithMessage<T> extends Predicate<T> {
+
+  /**
+   * The error message to display when predicate checks param. Only makes sense to
+   * call this method is apply(param) returns false.
+   */
+  public String getErrorReason(T param);
+
+}