Accept an empty string as the label value

smack-extensions/src/main/java/org/jivesoftware/smackx/xdata/FormField.java

@@ -33,6 +33,7 @@ import org.jivesoftware.smack.util.CollectionUtil;
 import org.jivesoftware.smack.util.EqualsUtil;
 import org.jivesoftware.smack.util.HashCode;
 import org.jivesoftware.smack.util.MultiMap;
+import org.jivesoftware.smack.util.Objects;
 import org.jivesoftware.smack.util.StringUtils;
 import org.jivesoftware.smack.util.XmlStringBuilder;
 
@@ -600,7 +601,7 @@ public abstract class FormField implements XmlElement {
          * @return a reference to this builder.
          */
         public B setLabel(String label) {
-            this.label = StringUtils.requireNotNullNorEmpty(label, "label must not be null or empty");
+            this.label = Objects.requireNonNull(label, "label must not be null");
             return getThis();
         }
 

smack-extensions/src/test/java/org/jivesoftware/smackx/xdata/FormFieldTest.java

@@ -17,6 +17,8 @@
 package org.jivesoftware.smackx.xdata;
 
 import static org.jivesoftware.smack.test.util.XmlAssertUtil.assertXmlSimilar;
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertThrows;
 
 import org.junit.jupiter.api.Test;
 import org.jxmpp.jid.JidTestUtil;
@@ -35,4 +37,18 @@ class FormFieldTest {
         assertXmlSimilar(expectedXml, xml);
     }
 
+    @Test
+    public void testEmptyLabel() {
+        TextSingleFormField.Builder builder = FormField.textSingleBuilder("type");
+        builder.setLabel("");
+        TextSingleFormField formField = builder.build();
+
+        assertEquals("", formField.getLabel());
+    }
+
+    @Test
+    public void testThrowExceptionWhenNullLabel() {
+        TextSingleFormField.Builder builder = FormField.textSingleBuilder("type");
+        assertThrows(IllegalArgumentException.class, () -> builder.setLabel(null));
+    }
 }

smack-extensions/src/test/java/org/jivesoftware/smackx/xdata/provider/DataFormProviderTest.java

@@ -115,4 +115,33 @@ public class DataFormProviderTest {
         assertEquals(2, items.size());
     }
 
+    @Test
+    public void testRetrieveFieldWithEmptyLabel() throws XmlPullParserException, IOException, SmackParsingException {
+
+        String form =
+                "<x xmlns='jabber:x:data' type='form'>" +
+                        "  <title>Advanced User Search</title>" +
+                        "  <instructions>The following fields are available for searching. Wildcard (*) characters are allowed as part of the query.</instructions>" +
+                        "  <field var='FORM_TYPE' label='' type='hidden'>" +
+                        "    <value>jabber:iq:search</value>" +
+                        "  </field>" +
+                        "  <field label='Search' var='search'>" +
+                        "    <required/>" +
+                        "  </field>" +
+                        "  <field label='Username' var='Username' type='boolean'>" +
+                        "    <value>true</value>" +
+                        "  </field>" +
+                        "  <field label='Name' var='Name' type='boolean'>" +
+                        "    <value>true</value>" +
+                        "  </field>" +
+                        "  <field label='Email' var='Email' type='boolean'>" +
+                        "    <value>true</value>" +
+                        "  </field>" +
+                        "</x>";
+        XmlPullParser parser = PacketParserUtils.getParserFor(form);
+        DataForm dataForm = DataFormProvider.INSTANCE.parse(parser);
+        FormField usernameFormField = dataForm.getField("FORM_TYPE");
+        assertEquals(FormField.Type.hidden, usernameFormField.getType());
+        assertEquals("", usernameFormField.getLabel());
+    }
 }