@AutoCodec: allow CONSTRUCTOR strategy to be used with dependency ele…

…ment.

It's very common for a child to need a dependency that the parent does not.
This eliminates the need for a `@AutoCodec.Dependency D unusedDependency'
constructor parameter.

* Adds a marshaller for HashCode.

PiperOrigin-RevId: 180989432

src/main/java/com/google/devtools/build/lib/skyframe/serialization/autocodec/AutoCodec.java

@@ -92,7 +92,7 @@ public static enum Strategy {
    * com.google.devtools.build.lib.skyframe.serialization.InjectingObjectCodec#deserialize}.
    *
    * <p>A compiler error will result if more than one constructor parameter has the
-   * {@code @Dependency} annotation.
+   * {@code @Dependency} annotation or if the annotation itself has a dependency element.
    */
   @Target(ElementType.PARAMETER)
   public static @interface Dependency {}
@@ -106,8 +106,7 @@ public static enum Strategy {
    * {@link com.google.devtools.build.lib.skyframe.serialization.ObjectCodec} with the dependency
    * type parameter matching the returned type.
    *
-   * <p>This is for use with {@code PUBLIC_FIELDS}, and {@code POLYMORPHIC} strategies. It is an
-   * error to use this with the {@code CONSTRUCTOR} strategy.
+   * <p>It is an error to use this in conjunction with {@code @AutoCodec.Dependency}.
    */
   Class<?> dependency() default Void.class;
 }

src/main/java/com/google/devtools/build/lib/skyframe/serialization/autocodec/AutoCodecProcessor.java

@@ -97,13 +97,7 @@ public boolean process(Set<? extends TypeElement> annotations, RoundEnvironment
       TypeSpec.Builder codecClassBuilder = null;
       switch (annotation.strategy()) {
         case CONSTRUCTOR:
-          if (dependencyType != null) {
-            throw new IllegalArgumentException(
-                encodedType.getQualifiedName()
-                    + " uses the CONSTRUCTOR strategy and has a non-Void dependency "
-                    + dependencyType.getQualifiedName());
-          }
-          codecClassBuilder = buildClassWithConstructorStrategy(encodedType);
+          codecClassBuilder = buildClassWithConstructorStrategy(encodedType, dependencyType);
           break;
         case PUBLIC_FIELDS:
           codecClassBuilder = buildClassWithPublicFieldsStrategy(encodedType, dependencyType);
@@ -150,9 +144,20 @@ private TypeElement getDependencyType(AutoCodec annotation) {
     }
   }
 
-  private TypeSpec.Builder buildClassWithConstructorStrategy(TypeElement encodedType) {
+  private TypeSpec.Builder buildClassWithConstructorStrategy(
+      TypeElement encodedType, @Nullable TypeElement dependency) {
     ExecutableElement constructor = selectConstructorForConstructorStrategy(encodedType);
     PartitionedParameters parameters = isolateDependency(constructor);
+    if (dependency != null) {
+      if (parameters.dependency != null) {
+        throw new IllegalArgumentException(
+            encodedType.getQualifiedName()
+                + " has both a @Dependency annotated constructor parameter "
+                + "and a non-Void dependency element "
+                + dependency.getQualifiedName());
+      }
+      parameters.dependency = dependency;
+    }
 
     TypeSpec.Builder codecClassBuilder =
         AutoCodecUtil.initializeCodecClassBuilder(encodedType, parameters.dependency);
@@ -174,11 +179,7 @@ private TypeSpec.Builder buildClassWithConstructorStrategy(TypeElement encodedTy
   private static class PartitionedParameters {
     /** Non-dependency parameters. */
     List<VariableElement> fields;
-    /**
-     * Parameter having the {@link AutoCodec.Dependency} annotation.
-     *
-     * <p>Null if no such parameter exists.
-     */
+    /** Dependency for this codec or null if no such dependency exists. */
     @Nullable TypeElement dependency;
   }
 

src/main/java/com/google/devtools/build/lib/skyframe/serialization/autocodec/Marshallers.java

@@ -22,6 +22,7 @@
 import com.google.common.collect.ImmutableSortedMap;
 import com.google.common.collect.ImmutableSortedSet;
 import com.google.common.collect.Maps;
+import com.google.common.hash.HashCode;
 import com.google.devtools.build.lib.skyframe.serialization.InjectingObjectCodec;
 import com.google.devtools.build.lib.skyframe.serialization.ObjectCodec;
 import com.google.devtools.build.lib.skyframe.serialization.autocodec.Marshaller.Context;
@@ -421,6 +422,26 @@ public void addDeserializationCode(Context context) {
         }
       };
 
+  /** Since we cannot add a codec to {@link HashCode}, it needs to be supported natively. */
+  private final Marshaller hashCodeMarshaller =
+      new Marshaller() {
+        @Override
+        public boolean matches(DeclaredType type) {
+          return matchesType(type, HashCode.class);
+        }
+
+        @Override
+        public void addSerializationCode(Context context) {
+          context.builder.addStatement("codedOut.writeByteArrayNoTag($L.asBytes())", context.name);
+        }
+
+        @Override
+        public void addDeserializationCode(Context context) {
+          context.builder.addStatement(
+              "$L = $T.fromBytes(codedIn.readByteArray())", context.name, HashCode.class);
+        }
+      };
+
   private final Marshaller protoMarshaller =
       new Marshaller() {
         @Override
@@ -484,6 +505,7 @@ public void addDeserializationCode(Context context) {
           mapMarshaller,
           multimapMarshaller,
           patternMarshaller,
+          hashCodeMarshaller,
           protoMarshaller,
           codecMarshaller);