docs/attachments/LUCENE-8908/SOLR-7845.patch

diff --git a/lucene/queries/src/java/org/apache/lucene/queries/function/valuesource/QueryValueSource.java b/lucene/queries/src/java/org/apache/lucene/queries/function/valuesource/QueryValueSource.java
index e535b55018f..a19665c4b31 100644
--- a/lucene/queries/src/java/org/apache/lucene/queries/function/valuesource/QueryValueSource.java
+++ b/lucene/queries/src/java/org/apache/lucene/queries/function/valuesource/QueryValueSource.java
@@ -185,10 +185,11 @@ class QueryDocValues extends FloatDocValues {
     }
   }
 
-   @Override
+  @Override
   public Object objectVal(int doc) {
      try {
-       return exists(doc) ? scorer.score() : null;
+       // shouldn't we just use floatVal(doc)?
+       return exists(doc) ? scorer.score() : defVal;
      } catch (IOException e) {
        throw new RuntimeException("caught exception in QueryDocVals("+q+") doc="+doc, e);
      }
diff --git a/lucene/queries/src/test/org/apache/lucene/queries/function/TestValueSources.java b/lucene/queries/src/test/org/apache/lucene/queries/function/TestValueSources.java
index ccdb0d34f87..2aed76f5464 100644
--- a/lucene/queries/src/test/org/apache/lucene/queries/function/TestValueSources.java
+++ b/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;
@@ -420,6 +421,16 @@ 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);
     }
@@ -512,7 +523,7 @@ 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 {
diff --git a/solr/core/src/test/org/apache/solr/search/function/TestFunctionQuery.java b/solr/core/src/test/org/apache/solr/search/function/TestFunctionQuery.java
index 499bb6eec2c..947c97c3cc5 100644
--- a/solr/core/src/test/org/apache/solr/search/function/TestFunctionQuery.java
+++ b/solr/core/src/test/org/apache/solr/search/function/TestFunctionQuery.java
@@ -1040,6 +1040,38 @@ 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();