1 files changed, 41 insertions, 0 deletions
diff --git a/src/main/java/com/google/devtools/build/lib/syntax/SkylarkValue.java b/src/main/java/com/google/devtools/build/lib/syntax/SkylarkValue.java
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index 0000000000..b93b0cda18
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+++ b/src/main/java/com/google/devtools/build/lib/syntax/SkylarkValue.java
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+// Copyright 2015 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;
+
+/**
+ * Java objects that are also Skylark values.
+ *
+ * <p>This is used for extending the Skylark interpreted with domain-specific values.
+ */
+public interface SkylarkValue {
+
+  /**
+   * Returns if the value is immutable and thus suitable for being used as a dictionary key.
+   *
+   * <p>Immutability is deep, i.e. in order for a value to be immutable, all values it is composed
+   * of must be immutable, too.
+   */
+  boolean isImmutable();
+
+  /**
+   * Print an official representation of object x.
+   *
+   * <p>For regular data structures, the value should be parsable back into an equal data structure.
+   *
+   * @param buffer the buffer to append the representation to
+   * @param quotationMark The quote style (" or ') to be used
+   */
+  void write(Appendable buffer, char quotationMark);
+}