GITHUB#15480 Make SortField.comparatorSource final

lucene/CHANGES.txt

@@ -58,6 +58,8 @@ API Changes
 
 * GITHUB#15295 : Switched to a fixed CFS threshold (Shubham Sharma)
 
+* GITHUB#15480: Deprecate SortField#setMissingValue and add migration test toward immutability. (Syed Mohammad Saad)
+
 New Features
 ---------------------
 

lucene/core/src/java/org/apache/lucene/search/SortField.java

@@ -131,7 +131,7 @@ public enum Type {
   private FieldComparatorSource comparatorSource;
 
   // Used for 'sortMissingFirst/Last'
-  protected final Object missingValue;
+  protected Object missingValue;
 
   // Indicates if sort should be optimized with indexed data. Set to true by default.
   @Deprecated private boolean optimizeSortWithIndexedData = true;
@@ -332,6 +332,17 @@ public Object getMissingValue() {
     return missingValue;
   }
 
+  /**
+   * Sets the value to use for documents that don't have a value.
+   *
+   * @deprecated Use {@link #SortField(String, Type, boolean, Object)} to supply missing values at
+   *     construction time. This method will be removed in Lucene 11.
+   */
+  @Deprecated
+  public void setMissingValue(Object missingValue) {
+    this.missingValue = missingValue;
+  }
+
   // Sets field & type, and ensures field is not NULL unless
   // type is SCORE or DOC
   private void validateField(String field, Type type, Object missingValue) {

lucene/core/src/test/org/apache/lucene/search/TestSortFieldMissingValue.java

@@ -0,0 +1,42 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You 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 test.org.apache.lucene.search;
+
+import org.apache.lucene.search.SortField;
+import org.apache.lucene.tests.util.LuceneTestCase;
+
+public class TestSortFieldMissingValue extends LuceneTestCase {
+
+  @SuppressWarnings("deprecation")
+  public void testDeprecatedSetterStillWorks() {
+    SortField a = new SortField("age", SortField.Type.INT);
+    a.setMissingValue(0);
+
+    SortField b = new SortField("age", SortField.Type.INT, false, 0);
+
+    assertEquals(b, a);
+    assertEquals(a.hashCode(), b.hashCode());
+  }
+
+  public void testNullMissingValue() {
+    SortField a = new SortField("age", SortField.Type.INT);
+    SortField b = new SortField("age", SortField.Type.INT, false, null);
+
+    assertEquals(b, a);
+  }
+}