SOLR-13783: Add space after comma in NamedList.toString() (#979)

solr/CHANGES.txt

@@ -31,6 +31,10 @@ Jetty 9.4.19.v20190610
 Upgrade Notes
 ----------------------
 
+* SOLR-13783: In situations where a NamedList must be output as plain text, commas between key-value pairs will now be
+  followed by a space (e.g. {shape=square, color=yellow} rather than {shape=square,color=yellow}) for consistency with
+  other java.util.Map implementations based on AbstractMap (Chris Hennick).
+
 * LUCENE-8738: Move to Java 11 as minimum Java version.
   (Adrien Grand, Uwe Schindler)
 

solr/solrj/src/java/org/apache/solr/common/util/NamedList.java

@@ -401,7 +401,7 @@ public class NamedList<T> implements Cloneable, Serializable, Iterable<Map.Entry
     sb.append('{');
     int sz = size();
     for (int i=0; i<sz; i++) {
-      if (i != 0) sb.append(',');
+      if (i != 0) sb.append(", ");
       sb.append(getName(i));
       sb.append('=');
       sb.append(getVal(i));

solr/solrj/src/test/org/apache/solr/common/util/NamedListTest.java

@@ -26,6 +26,16 @@ import org.junit.Test;
 
 public class NamedListTest extends SolrTestCase {
 
+  @Test
+  public void testToString() {
+    NamedList<String> nl = new NamedList<>();
+    assertEquals("{}", nl.toString());
+    nl.add("key1", "value1");
+    assertEquals("{key1=value1}", nl.toString());
+    nl.add("key2", "value2");
+    assertEquals("{key1=value1, key2=value2}", nl.toString());
+  }
+
   public void testRemove() {
     NamedList<String> nl = new NamedList<>();
     nl.add("key1", "value1");