LUCENE-8908: return def val from objectVal when exists returns false

* This behavior is similar to floatVal in QueryValueSource

lucene/CHANGES.txt

@@ -139,6 +139,9 @@ Bug Fixes
 * LUCENE-9164: Ensure IW processes all internal events before it closes itself on a rollback.
   (Simon Willnauer, Nhat Nguyen, Dawid Weiss, Mike Mccandless)
 
+* LUCENE-8908: Return default value from objectVal when doc doesn't match the query in QueryValueSource
+  (Bill Bell, hossman, Munendra S N, Michele Palmia)
+
 Other
 ---------------------
 

lucene/queries/src/java/org/apache/lucene/queries/function/valuesource/QueryValueSource.java

@@ -166,11 +166,7 @@ class QueryDocValues extends FloatDocValues {
 
   @Override
   public Object objectVal(int doc) {
-    try {
-      return exists(doc) ? scorer.score() : null;
-    } catch (IOException e) {
-      throw new RuntimeException("caught exception in QueryDocVals(" + q + ") doc=" + doc, e);
-    }
+    return floatVal(doc);
   }
 
   @Override

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

@@ -41,6 +41,7 @@ import org.apache.lucene.queries.function.valuesource.*;
 import org.apache.lucene.search.CheckHits;
 import org.apache.lucene.search.DoubleValuesSource;
 import org.apache.lucene.search.IndexSearcher;
+import org.apache.lucene.search.MatchNoDocsQuery;
 import org.apache.lucene.search.Query;
 import org.apache.lucene.search.ScoreDoc;
 import org.apache.lucene.search.ScoreMode;
@@ -424,6 +425,16 @@ public class TestValueSources extends LuceneTestCase {
       vs = new QueryValueSource(new TermQuery(new Term("bogus","does not exist")), 0F);
       assertNoneExist(vs);
 
+      // doc doesn't match the query, so default value should be returned
+      vs = new QueryValueSource(new MatchNoDocsQuery(), 5.0f);
+      final LeafReaderContext leaf = searcher.getIndexReader().leaves().get(0);
+      FunctionValues fv = vs.getValues(ValueSource.newContext(searcher), leaf);
+      assertEquals(5.0f, fv.objectVal(1));
+
+      // test with def value but doc matches the query, so def value shouldn't be returned
+      vs = new QueryValueSource(new TermQuery(new Term("text","test")), 2F);
+      fv = vs.getValues(ValueSource.newContext(searcher), leaf);
+      assertNotEquals(2f, fv.objectVal(1));
     } finally {
       searcher.setSimilarity(saved);
     }
@@ -516,7 +527,7 @@ public class TestValueSources extends LuceneTestCase {
     assertEquals("test(const(4.1),const(1.2),double(some_double)=0.0)", fv.toString(1));
 
   }
-  
+
   public void testTF() throws Exception {
     Similarity saved = searcher.getSimilarity();
     try {

solr/core/src/test/org/apache/solr/search/function/TestFunctionQuery.java

@@ -1039,6 +1039,38 @@ public class TestFunctionQuery extends SolrTestCaseJ4 {
                /*id*/1, /*score*/2);
   }
 
+  @Test
+  public void testQueryAsFlParam() {
+    clearIndex();
+
+    assertU(adoc("id", "1", "age_i", "35"));
+    assertU(adoc("id", "2", "age_i", "25"));
+    assertU(commit());
+
+    // some docs match the query func but some doesn't
+    // if doc doesn't match, it should use default value
+    assertQ(req("q", "*:*", "fl", "*,score,bleh:query($qq,5.0)", "qq", "id:2"),
+        "//*[@numFound='2']",
+        "//result/doc[1]/str[@name='id'][.='1']",
+        "//result/doc[2]/str[@name='id'][.='2']",
+        "//result/doc[1]/float[@name='bleh'][.='5.0']",
+        "count(//result/doc[2]/float[@name='bleh'][.='5.0'])=0",
+        "//result/doc[2]/float[@name='bleh']" // since score can't be known, doing existing match
+        );
+
+    // when the doc match the query func condition default value shouldn't be used
+    // when no def val is passed in query func, 0.0 would be used
+    assertQ(req("q", "*:*", "fl", "*,score,bleh:query($qq)", "qq", "id:*"),
+        "//*[@numFound='2']",
+        "//result/doc[1]/str[@name='id'][.='1']",
+        "//result/doc[2]/str[@name='id'][.='2']",
+        "count(//result/doc[1]/float[@name='bleh'][.='0.0'])=0",
+        "count(//result/doc[2]/float[@name='bleh'][.='0.0'])=0",
+        "//result/doc[1]/float[@name='bleh']",
+        "//result/doc[2]/float[@name='bleh']"
+    );
+  }
+
   @Test
   public void testEqualFunction() {
     clearIndex();