Update from Google.

--
MOE_MIGRATED_REVID=85702957

1 files changed, 60 insertions, 0 deletions

diff --git a/src/main/java/com/google/devtools/build/lib/analysis/TransitiveInfoProvider.java b/src/main/java/com/google/devtools/build/lib/analysis/TransitiveInfoProvider.java
new file mode 100644
index 0000000000..37ec1910cb
--- /dev/null
+++ b/src/main/java/com/google/devtools/build/lib/analysis/TransitiveInfoProvider.java
@@ -0,0 +1,60 @@
+// 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.analysis;
+
+/**
+ * This marker interface must be extended by every interface that represents
+ * rolled-up data about the transitive closure of a configured target.
+ *
+ * TransitiveInfoProviders need to be serializable, and for that reason they must conform to
+ * the following restrictions:
+ *
+ * <ul>
+ * <li>The provider interface must directly extend {@code TransitiveInfoProvider}.
+ * <li>Every method must return immutable data.</li>
+ * <li>Every method must return the same object if called multiple times with the same
+ * arguments.</li>
+ * <li>Overloading a method name multiple times is forbidden.</li>
+ * <li>The return type of a method must satisfy one of the following conditions:
+ * <ul>
+ * <li>It must be from the set of {String, Integer, int, Boolean, bool, Label, PathFragment,
+ * Artifact}, OR</li>
+ * <li>it must be an ImmutableList/List/Collection/Iterable of T, where T is either
+ * one of the types above with a default serializer or T implements ValueSerializer), OR</li>
+ * <li>it must be serializable (TBD)</li>
+ * </ul>
+ * <li>If the method takes arguments, it must declare a custom serializer (TBD).</li>
+ * </ul>
+ *
+ * <p>Some typical uses of this interface are:
+ * <ul>
+ * <li>The set of Python source files in the transitive closure of this rule
+ * <li>The set of declared C++ header files in the transitive closure
+ * <li>The files that need to be built when the target is mentioned on the command line
+ * </ul>
+ *
+ * <p>Note that if implemented naively, this would result in the memory requirements
+ * being O(n^2): in a long dependency chain, if every target adds one single artifact, storing the
+ * transitive closures of every rule would take 1+2+3+...+n-1+n = O(n^2) memory.
+ *
+ * <p>In order to avoid this, we introduce the concept of nested sets. A nested set is an immutable
+ * data structure that can contain direct members and other nested sets (recursively). Nested sets
+ * are iterable and can be flattened into ordered sets, where the order depends on which
+ * implementation of NestedSet you pick.
+ *
+ * @see TransitiveInfoCollection
+ */
+public interface TransitiveInfoProvider {
+}