Add EnumMapCodec. Some hackery necessary to get Class for Enum when map is empty.

Since EnumMap.equals() ignores the key type when the maps are empty [1], we could just return a canonical empty EnumMap, but that seems to depend on implementation details in a hacky and potentially subtly broken way. The Unsafe method will hopefully break spectacularly if it goes wrong.

[1] http://hg.openjdk.java.net/jdk8/jdk8/jdk/file/687fd7c7986d/src/share/classes/java/util/EnumMap.java#l685

PiperOrigin-RevId: 189803280

1 files changed, 64 insertions, 0 deletions

diff --git a/src/test/java/com/google/devtools/build/lib/skyframe/serialization/EnumMapCodecTest.java b/src/test/java/com/google/devtools/build/lib/skyframe/serialization/EnumMapCodecTest.java
new file mode 100644
index 0000000000..93400620cb
--- /dev/null
+++ b/src/test/java/com/google/devtools/build/lib/skyframe/serialization/EnumMapCodecTest.java
@@ -0,0 +1,64 @@
+// 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 static com.google.common.truth.Truth.assertThat;
+import static com.google.devtools.build.lib.testutil.MoreAsserts.assertThrows;
+
+import com.google.common.collect.ImmutableMap;
+import com.google.devtools.build.lib.skyframe.serialization.testutils.SerializationTester;
+import com.google.devtools.build.lib.skyframe.serialization.testutils.TestUtils;
+import java.util.EnumMap;
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.junit.runners.JUnit4;
+
+/** Tests for {@link EnumMapCodec}. */
+@RunWith(JUnit4.class)
+public class EnumMapCodecTest {
+  @Test
+  public void smoke() throws Exception {
+    new SerializationTester(
+            new EnumMap<>(
+                ImmutableMap.of(
+                    TestEnum.FIRST, "first", TestEnum.THIRD, "third", TestEnum.SECOND, "second")),
+            new EnumMap<>(TestEnum.class),
+            new EnumMap<>(EmptyEnum.class))
+        .runTests();
+  }
+
+  @Test
+  public void throwsOnSubclass() {
+    SerializationException exception =
+        assertThrows(
+            SerializationException.class,
+            () -> TestUtils.toBytes(new SubEnum<>(TestEnum.class), ImmutableMap.of()));
+    assertThat(exception).hasMessageThat().contains("Cannot serialize subclasses of EnumMap");
+  }
+
+  private enum TestEnum {
+    FIRST,
+    SECOND,
+    THIRD
+  }
+
+  private enum EmptyEnum {}
+
+  private static class SubEnum<E extends Enum<E>, V> extends EnumMap<E, V> {
+    public SubEnum(Class<E> keyType) {
+      super(keyType);
+    }
+  }
+}