SOLR-9740: fix macro expansion of multi-valued parameters

solr/CHANGES.txt

@@ -136,6 +136,11 @@ Bug Fixes
   of matching something due to filter exclusions (which can widen the domain again).
   (Michael Sun, yonik)
 
+* SOLR-9740: A bug in macro expansion of multi-valued parameters caused non-expanded values
+  after the first expanded value in the same multi-valued parameter to be dropped.
+  (Erik Hatcher, yonik)
+
+
 Other Changes
 ----------------------
 

solr/core/src/java/org/apache/solr/request/macro/MacroExpander.java

@@ -71,6 +71,8 @@ public class MacroExpander {
               newValues.add(vv);
             }
           }
+        }
+        if (newValues != null) {
           newValues.add(newV);
         }
       }

solr/core/src/test/org/apache/solr/request/macro/TestMacroExpander.java

@@ -113,4 +113,17 @@ public class TestMacroExpander extends LuceneTestCase {
     }
   }
 
+  @Test
+  public void testMap() { // see SOLR-9740, the second fq param was being dropped.
+    final Map<String,String[]> request = new HashMap<>();
+    request.put("fq", new String[] {"zero", "${one_ref}", "two", "${three_ref}"});
+    request.put("one_ref",new String[] {"one"});
+    request.put("three_ref",new String[] {"three"});
+    Map expanded = MacroExpander.expand(request);
+    assertEquals("zero", ((String[])expanded.get("fq"))[0]);
+    assertEquals("one", ((String[])expanded.get("fq"))[1]);
+    assertEquals("two", ((String[]) expanded.get("fq"))[2]);
+    assertEquals("three", ((String[]) expanded.get("fq"))[3]);
+  }
+
 }