Override ValueSource.FromDoubleValuesSource.getSortField (apache#14654)

Add ValueSource.FromDoubleValuesSource.getSortField
Thus reducing indirection and supporting needsScores correctly (fixes a bug).

Author: dsmiley

lucene/CHANGES.txt

@@ -113,7 +113,8 @@ Optimizations
 
 Bug Fixes
 ---------------------
-(No changes)
+* GITHUB#14654: ValueSource.fromDoubleValuesSource(dvs).getSortField() would throw errors when
+  used if the DoubleValuesSource needed scores. (David Smiley)
 
 Build
 ---------------------

lucene/queries/src/java/org/apache/lucene/queries/function/ValueSource.java

@@ -319,6 +319,12 @@ public boolean exists(int doc) throws IOException {
       };
     }
 
+    @Override
+    public SortField getSortField(boolean reverse) {
+      // avoids indirection and supports a better needsScores()
+      return in.getSortField(reverse);
+    }
+
     @Override
     public boolean equals(Object o) {
       if (this == o) return true;

lucene/queries/src/test/org/apache/lucene/queries/function/TestValueSources.java

@@ -876,6 +876,31 @@ public void testBuildingFromDoubleValues() throws Exception {
         new FunctionQuery(ValueSource.fromDoubleValuesSource(dvs)), new float[] {3.63f, 5.65f});
   }
 
+  public void testFromDoubleValuesSortWithScore() throws Exception {
+    // Create a query that matches all documents
+    var query = new TermQuery(new Term("text", "test"));
+
+    // Get the original scores
+    TopDocs originalDocs = searcher.search(query, documents.size());
+    ScoreDoc[] originalScoreDocs = originalDocs.scoreDocs;
+
+    // Use a DoubleValuesSource that references the score and convert it to a ValueSource
+    ValueSource scoreSource = ValueSource.fromDoubleValuesSource(DoubleValuesSource.SCORES);
+    SortField sortField = scoreSource.getSortField(true); // true for reverse (descending)
+    Sort sort = new Sort(sortField);
+
+    // Search with the sort.
+    //   note: used to fail with an assertion before fromDoubleValuesSource's impl was improved
+    TopDocs sortedDocs = searcher.search(query, documents.size(), sort);
+    ScoreDoc[] sortedScoreDocs = sortedDocs.scoreDocs;
+
+    // Verify we got the same docs in-order but don't check the scores
+    assertEquals(originalScoreDocs.length, sortedScoreDocs.length);
+    for (int i = 0; i < originalScoreDocs.length; i++) {
+      assertEquals(originalScoreDocs[i].doc, sortedScoreDocs[i].doc);
+    }
+  }
+
   /**
    * Asserts that for every doc, the {@link FunctionValues#exists} value from the {@link
    * ValueSource} is <b>true</b>.