Adds codecs for more list variants.

PiperOrigin-RevId: 189417853

2 files changed, 99 insertions, 26 deletions

diff --git a/src/main/java/com/google/devtools/build/lib/skyframe/serialization/ArrayListCodec.java b/src/main/java/com/google/devtools/build/lib/skyframe/serialization/ArrayListCodec.java
index e768e8426c..03453f6784 100644
--- a/src/main/java/com/google/devtools/build/lib/skyframe/serialization/ArrayListCodec.java
+++ b/src/main/java/com/google/devtools/build/lib/skyframe/serialization/ArrayListCodec.java
@@ -14,40 +14,24 @@
 
 package com.google.devtools.build.lib.skyframe.serialization;
 
-import com.google.protobuf.CodedInputStream;
-import com.google.protobuf.CodedOutputStream;
-import java.io.IOException;
+import com.google.common.collect.ImmutableList;
 import java.util.ArrayList;
+import java.util.List;
 
-@SuppressWarnings("rawtypes")
-class ArrayListCodec implements ObjectCodec<ArrayList> {
-
+class ArrayListCodec<T> extends NullableListCodec<T> {
+  @SuppressWarnings("unchecked")
   @Override
-  public Class<ArrayList> getEncodedClass() {
-    return ArrayList.class;
+  public Class<List<T>> getEncodedClass() {
+    return (Class<List<T>>) (Class<?>) ArrayList.class;
   }
 
   @Override
-  public void serialize(SerializationContext context, ArrayList list, CodedOutputStream codedOut)
-      throws IOException, SerializationException {
-    codedOut.writeInt32NoTag(list.size());
-    for (Object obj : list) {
-      context.serialize(obj, codedOut);
-    }
+  public List<Class<? extends List<T>>> additionalEncodedClasses() {
+    return ImmutableList.of();
   }
 
   @Override
-  public ArrayList deserialize(DeserializationContext context, CodedInputStream codedIn)
-      throws SerializationException, IOException {
-    int length = codedIn.readInt32();
-    if (length < 0) {
-      throw new SerializationException("Expected non-negative length: " + length);
-    }
-
-    ArrayList<Object> list = new ArrayList<>(length);
-    for (int i = 0; i < length; ++i) {
-      list.add(context.deserialize(codedIn));
-    }
-    return list;
+  protected List<T> maybeTransform(ArrayList<T> startingList) {
+    return startingList;
   }
 }
diff --git a/src/main/java/com/google/devtools/build/lib/skyframe/serialization/NullableListCodec.java b/src/main/java/com/google/devtools/build/lib/skyframe/serialization/NullableListCodec.java
new file mode 100644
index 0000000000..bd3cf2c30e
--- /dev/null
+++ b/src/main/java/com/google/devtools/build/lib/skyframe/serialization/NullableListCodec.java
@@ -0,0 +1,89 @@
+// Copyright 2018 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.skyframe.serialization;
+
+import com.google.common.collect.ImmutableList;
+import com.google.protobuf.CodedInputStream;
+import com.google.protobuf.CodedOutputStream;
+import java.io.IOException;
+import java.util.AbstractList;
+import java.util.ArrayList;
+import java.util.Collections;
+import java.util.LinkedList;
+import java.util.List;
+
+/**
+ * Encodes a list of elements, each of which may be null. Unless explicitly specified as the codec,
+ * lists will only use this codec if they extend {@link AbstractList} or are one of {@link
+ * #RANDOM_ACCESS_TYPE} or {@link #SEQUENTIAL_ACCESS_TYPE} (intented to capture unmodifiable
+ * versions of normal lists).
+ */
+class NullableListCodec<T> implements ObjectCodec<List<T>> {
+  @SuppressWarnings("unchecked")
+  private static final Class<? extends List<?>> RANDOM_ACCESS_TYPE =
+      (Class<? extends List<?>>) Collections.unmodifiableList(new ArrayList<>()).getClass();
+  // Need linked list to get sequential access class type.
+  @SuppressWarnings({"unchecked", "JdkObsolete"})
+  private static final Class<? extends List<?>> SEQUENTIAL_ACCESS_TYPE =
+      (Class<? extends List<?>>) Collections.unmodifiableList(new LinkedList<>()).getClass();
+
+  // Needed due to generics / type erasure.
+  @SuppressWarnings("unchecked")
+  @Override
+  public Class<List<T>> getEncodedClass() {
+    // We return AbstractList here because List is an interface, so it will never be hit in the
+    // ancestor traversal of a concrete class.
+    return cast(AbstractList.class);
+  }
+
+  @SuppressWarnings("unchecked")
+  @Override
+  public List<Class<? extends List<T>>> additionalEncodedClasses() {
+    return ImmutableList.of(cast(RANDOM_ACCESS_TYPE), cast(SEQUENTIAL_ACCESS_TYPE));
+  }
+
+  @Override
+  public void serialize(SerializationContext context, List<T> list, CodedOutputStream codedOut)
+      throws SerializationException, IOException {
+    codedOut.writeInt32NoTag(list.size());
+    for (T item : list) {
+      context.serialize(item, codedOut);
+    }
+  }
+
+  @Override
+  public List<T> deserialize(DeserializationContext context, CodedInputStream codedIn)
+      throws SerializationException, IOException {
+    int length = codedIn.readInt32();
+    if (length < 0) {
+      throw new SerializationException("Expected non-negative length: " + length);
+    }
+
+    ArrayList<T> list = new ArrayList<>(length);
+    for (int i = 0; i < length; i++) {
+      list.add(context.deserialize(codedIn));
+    }
+    return maybeTransform(list);
+  }
+
+  protected List<T> maybeTransform(ArrayList<T> startingList) {
+    return Collections.unmodifiableList(startingList);
+  }
+
+  @SuppressWarnings({"unchecked", "rawtypes"}) // Raw List.
+  private Class<List<T>> cast(Class<? extends List> clazz) {
+    return (Class<List<T>>) clazz;
+  }
+}