1 files changed, 43 insertions, 0 deletions
diff --git a/src/main/java/com/google/devtools/build/lib/analysis/skylark/SkylarkApiProvider.java b/src/main/java/com/google/devtools/build/lib/analysis/skylark/SkylarkApiProvider.java
new file mode 100644
index 0000000000..153f7beb61
--- /dev/null
+++ b/src/main/java/com/google/devtools/build/lib/analysis/skylark/SkylarkApiProvider.java
@@ -0,0 +1,43 @@
+// Copyright 2014 The Bazel Authors. 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.analysis.skylark;
+
+import com.google.devtools.build.lib.analysis.TransitiveInfoCollection;
+import com.google.devtools.build.lib.util.Preconditions;
+
+/**
+ * An abstract class for adding a Skylark API for the native providers.
+ * Derived classes should declare functions to be used from Skylark.
+ */
+public abstract class SkylarkApiProvider {
+  private TransitiveInfoCollection info;
+
+  protected TransitiveInfoCollection getInfo() {
+    return info;
+  }
+
+  public final void init(TransitiveInfoCollection info) {
+    if (this.info != null) {
+      // todo(dslomov): nuke this weird initialization mechanism.
+
+      // Allow multiple calls.
+      // It is possible for the Skylark rule to get a SkylarkApiProvider such as `target.java`
+      // from its dependency and pass it on. It does not make a whole lot of sense, but we
+      // shouldn't crash.
+      return;
+    }
+    this.info = Preconditions.checkNotNull(info);
+  }
+}