Enhancement: First field in repeating group as delimiter

quickfixj-core/src/main/doc/usermanual/usage/configuration.html

@@ -464,6 +464,14 @@ <H3>QuickFIX Settings</H3>
     <TD> Y<br>N</TD>
     <TD> Y </TD>
   </TR>
+  <TR ALIGN="left" VALIGN="middle">
+      <TD><I>FirstFieldInGroupIsDelimiter</I></TD>
+      <TD>Session validation setting for enabling whether first found field in repeating group will be used as
+          delimiter. Values are "Y" or "N". Default is "N".</TD>
+      <TD>Y<br>
+          N</TD>
+      <TD>N</TD>
+  </TR>
 
   <TR ALIGN="center" VALIGN="middle">
     <TD COLSPAN="4" class="subsection"><A NAME="Initiator">Initiator</A></TD>

quickfixj-core/src/main/java/quickfix/DataDictionary.java

@@ -93,6 +93,7 @@ private static Supplier<DocumentBuilderFactory> createDocumentBuilderFactorySupp
     private boolean checkUserDefinedFields = true;
     private boolean checkUnorderedGroupFields = true;
     private boolean allowUnknownMessageFields = false;
+    private boolean firstFieldInGroupIsDelimiter = false;
     private String beginString;
     private String fullVersion;
     private String majorVersion;
@@ -561,6 +562,25 @@ public boolean isAllowUnknownMessageFields() {
         return allowUnknownMessageFields;
     }
 
+    public boolean isFirstFieldInGroupIsDelimiter() {
+        return firstFieldInGroupIsDelimiter;
+    }
+    /**
+     * Controls whether any field which is
+     * first in the group would be used as delimiter
+     *
+     * @param flag true = use first field from message, false = follow data dictionary
+     * Must be used with enabled {@link #setCheckUnorderedGroupFields(boolean)}
+     */
+    public void setFirstFieldInGroupIsDelimiter(boolean flag) {
+        firstFieldInGroupIsDelimiter = flag;
+        for (Map<Integer, GroupInfo> gm : groups.values()) {
+            for (GroupInfo gi : gm.values()) {
+                gi.getDataDictionary().setFirstFieldInGroupIsDelimiter(flag);
+            }
+        }
+    }
+
     /**
      * Controls whether group fields are in the same order
      *
@@ -638,6 +658,7 @@ private void copyFrom(DataDictionary rhs) {
         setCheckUserDefinedFields(rhs.checkUserDefinedFields);
         setCheckUnorderedGroupFields(rhs.checkUnorderedGroupFields);
         setAllowUnknownMessageFields(rhs.allowUnknownMessageFields);
+        setFirstFieldInGroupIsDelimiter(rhs.firstFieldInGroupIsDelimiter);
 
         calculateOrderedFields();
     }

quickfixj-core/src/main/java/quickfix/DefaultSessionFactory.java

@@ -309,6 +309,11 @@ private DataDictionary createDataDictionary(SessionID sessionID, SessionSettings
                     Session.SETTING_ALLOW_UNKNOWN_MSG_FIELDS));
         }
 
+        if (settings.isSetting(sessionID, Session.SETTING_FIRST_FIELD_IN_GROUP_IS_DELIMITER)) {
+            dataDictionary.setFirstFieldInGroupIsDelimiter(settings.getBool(sessionID,
+                    Session.SETTING_FIRST_FIELD_IN_GROUP_IS_DELIMITER));
+        }
+
         return dataDictionary;
     }
 

quickfixj-core/src/main/java/quickfix/Message.java

@@ -723,7 +723,7 @@ private void parseGroup(String msgType, StringField field, DataDictionary dd, Da
             throw MessageUtils.newInvalidMessageException("Repeating group count requires an Integer but found '" + field.getValue() + "' in " + messageData, this);
         }
         parent.setField(groupCountTag, field);
-        final int firstField = rg.getDelimiterField();
+        int firstField = groupDataDictionary.isFirstFieldInGroupIsDelimiter() ? -1 : rg.getDelimiterField();
         Group group = null;
         boolean inGroupParse = true;
         while (inGroupParse) {
@@ -733,7 +733,9 @@ private void parseGroup(String msgType, StringField field, DataDictionary dd, Da
                 break;
             }
             int tag = field.getTag();
-            if (tag == firstField) {
+            boolean shouldCreateNewGroup = tag == firstField || (groupDataDictionary.isFirstFieldInGroupIsDelimiter() && firstField < 0);
+            if (shouldCreateNewGroup) {
+                firstField = tag;
                 addGroupRefToParent(group, parent);
                 group = new Group(groupCountTag, firstField, groupDataDictionary.getOrderedFields());
                 group.setField(field);

quickfixj-core/src/main/java/quickfix/Session.java

@@ -376,6 +376,12 @@ public class Session implements Closeable {
      */
     public static final String SETTING_RESEND_REQUEST_CHUNK_SIZE = "ResendRequestChunkSize";
 
+    /**
+     * Session validation setting for enabling whether first found field in repeating group will be used as
+     * delimiter. Values are "Y" or "N". Default is "N".
+     */
+    public static final String SETTING_FIRST_FIELD_IN_GROUP_IS_DELIMITER = "FirstFieldInGroupIsDelimiter";
+
     public static final String SETTING_MAX_SCHEDULED_WRITE_REQUESTS = "MaxScheduledWriteRequests";
 
     public static final String SETTING_VALIDATE_CHECKSUM = "ValidateChecksum";

quickfixj-core/src/test/java/quickfix/DataDictionaryTest.java

@@ -54,6 +54,7 @@
 import quickfix.field.TargetCompID;
 import quickfix.field.TimeInForce;
 import quickfix.field.TransactTime;
+import quickfix.fix44.NewOrderMultileg;
 import quickfix.fix44.NewOrderSingle;
 import quickfix.fix44.Quote;
 import quickfix.fix44.QuoteRequest;
@@ -78,6 +79,7 @@
 import static org.junit.Assert.assertNotNull;
 import static org.junit.Assert.assertTrue;
 import static org.junit.Assert.fail;
+import static org.junit.Assert.assertThrows;
 
 public class DataDictionaryTest {
 
@@ -1493,6 +1495,55 @@ private String getCommonDataDictionaryString(String data) {
         return data;
     }
 
+    @Test
+    public void testFirstFieldInGroupIsDelimiter() throws Exception {
+
+        final DataDictionary dataDictionary = new DataDictionary(getDictionary());
+        dataDictionary.setCheckUnorderedGroupFields(false);
+        dataDictionary.setFirstFieldInGroupIsDelimiter(true);
+
+        String fixMsg = "8=FIX.4.4\u00019=688\u000135=AB\u000149=AAA\u000156=BBB\u000134=21133\u000150=ABCABC" +
+                "\u000152=20230905-13:24:37.022\u000155=AAPL\u00011=ACC1\u000111=123456abcedf\u000121=1\u000138=5\u000154=1\u000140=2\u000144=-0.8" +
+                "\u000159=0\u000160=20230905-13:24:36.984\u0001100=ALGO\u0001167=MLEG\u0001555=3\u0001602=111\u0001600=AAA" +
+                "\u0001602=222\u0001654=231\u0001600=BBB\u0001602=333\u0001654=332\u0001600=CCC\u000158=TEXT\u000110=168\u0001";
+
+        String byDictFixMsg = "8=FIX.4.4\u00019=688\u000135=AB\u000149=AAA\u000156=BBB\u000134=21133\u000150=ABCABC" +
+                "\u000152=20230905-13:24:37.022\u000155=AAPL\u00011=ACC1\u000111=123456abcedf\u000121=1\u000138=5\u000154=1\u000140=2\u000144=-0.8" +
+                "\u000159=0\u000160=20230905-13:24:36.984\u0001100=ALGO\u0001167=MLEG\u0001555=3\u0001600=AAA\u0001602=111" +
+                "\u0001600=BBB\u0001602=222\u0001654=231\u0001600=CCC\u0001602=333\u0001654=332\u000158=TEXT\u000110=168\u0001";
+
+        //doValidation and firstFieldInGroupIsDelimiter -> should NOT fail
+        final NewOrderMultileg noml1 = new NewOrderMultileg();
+        noml1.fromString(fixMsg, dataDictionary, true);
+        dataDictionary.validate(noml1);
+        assertTrue(noml1.hasGroup(555));
+        assertEquals(3, noml1.getGroupCount(555));
+        //delimiter should be first tag in group
+        assertEquals(602, noml1.getGroup(1, 555).delim());
+
+        dataDictionary.setFirstFieldInGroupIsDelimiter(false);
+        dataDictionary.setCheckUnorderedGroupFields(true);
+        final NewOrderMultileg noml2 = new NewOrderMultileg();
+        noml2.fromString(fixMsg, dataDictionary, true);
+        //when firstFieldInGroupIsDelimiter = false and setCheckUnorderedGroupFields = true - exception is thrown
+        assertThrows(FieldException.class, () -> dataDictionary.validate(noml2));
+
+        final NewOrderMultileg noml3 = new NewOrderMultileg();
+        noml3.fromString(fixMsg, dataDictionary, true);
+        //when firstFieldInGroupIsDelimiter = true and setCheckUnorderedGroupFields = true - exception is thrown
+        assertThrows(FieldException.class, () -> dataDictionary.validate(noml3));
+
+        dataDictionary.setCheckUnorderedGroupFields(true);
+        final NewOrderMultileg noml4 = new NewOrderMultileg();
+        noml4.fromString(byDictFixMsg, dataDictionary, true);
+        //when firstFieldInGroupIsDelimiter = true and setCheckUnorderedGroupFields = true, message aligns with dictionary - do NOT fail
+        dataDictionary.validate(noml4);
+        assertTrue(noml4.hasGroup(555));
+        assertEquals(3, noml4.getGroupCount(555));
+        //delimiter should be dictionary first tag = 600
+        assertEquals(600, noml4.getGroup(1, 555).delim());
+    }
+
 
     //
     // Group Validation Tests in RepeatingGroupTest