1 files changed, 44 insertions, 0 deletions
diff --git a/src/main/java/com/google/devtools/build/lib/syntax/SkylarkCallbackFunction.java b/src/main/java/com/google/devtools/build/lib/syntax/SkylarkCallbackFunction.java
new file mode 100644
index 0000000000..2e94be8706
--- /dev/null
+++ b/src/main/java/com/google/devtools/build/lib/syntax/SkylarkCallbackFunction.java
@@ -0,0 +1,44 @@
+// 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.syntax;
+
+import com.google.common.collect.ImmutableList;
+
+
+/**
+ * A helper class for calling Skylark functions from Java.
+ */
+public class SkylarkCallbackFunction {
+
+  private final UserDefinedFunction callback;
+  private final FuncallExpression ast;
+  private final SkylarkEnvironment funcallEnv;
+
+  public SkylarkCallbackFunction(UserDefinedFunction callback, FuncallExpression ast,
+      SkylarkEnvironment funcallEnv) {
+    this.callback = callback;
+    this.ast = ast;
+    this.funcallEnv = funcallEnv;
+  }
+
+  public Object call(ClassObject ctx, Object... arguments) throws EvalException {
+    try {
+      return callback.call(
+          ImmutableList.<Object>builder().add(ctx).add(arguments).build(), null, ast, funcallEnv);
+    } catch (InterruptedException | ClassCastException
+        | IllegalArgumentException e) {
+      throw new EvalException(ast.getLocation(), e.getMessage());
+    }
+  }
+}