From 014e7ef150a860f06323692ceaa5a9f21874f678 Mon Sep 17 00:00:00 2001
From: Michael Williamson <mike@zwobble.org>
Date: Sun, 9 Aug 2026 15:03:03 +0100
Subject: Ignore numbering levels that use numStyleLink to refer to themselves

---
 .../zwobble/mammoth/internal/docx/Numbering.java    | 13 ++++++++++++-
 .../mammoth/tests/docx/NumberingXmlTests.java       | 21 +++++++++++++++++++++
 2 files changed, 33 insertions(+), 1 deletion(-)

(limited to 'src')

diff --git a/src/main/java/org/zwobble/mammoth/internal/docx/Numbering.java b/src/main/java/org/zwobble/mammoth/internal/docx/Numbering.java
index 1a39047..6213d13 100644
--- a/src/main/java/org/zwobble/mammoth/internal/docx/Numbering.java
+++ b/src/main/java/org/zwobble/mammoth/internal/docx/Numbering.java
@@ -4,8 +4,10 @@ import org.zwobble.mammoth.internal.documents.NumberingLevel;
 import org.zwobble.mammoth.internal.util.Iterables;
 import org.zwobble.mammoth.internal.util.Maps;
 
+import java.util.HashSet;
 import java.util.Map;
 import java.util.Optional;
+import java.util.Set;
 
 import static org.zwobble.mammoth.internal.util.Maps.lookup;
 import static org.zwobble.mammoth.internal.util.Maps.map;
@@ -86,6 +88,15 @@ public class Numbering {
     }
 
     public Optional<NumberingLevel> findLevel(String numId, String level) {
+        return findLevelWithSeenNumIds(numId, level, new HashSet<>());
+    }
+
+    public Optional<NumberingLevel> findLevelWithSeenNumIds(String numId, String level, Set<String> seenNumIds) {
+        if (seenNumIds.contains(numId)) {
+            return Optional.empty();
+        }
+        seenNumIds.add(numId);
+
         return lookup(nums, numId)
             .flatMap(num -> num.abstractNumId)
             .flatMap(abstractNumId -> lookup(this.abstractNums, abstractNumId))
@@ -94,7 +105,7 @@ public class Numbering {
                     return abstractNum.numStyleLink
                         .flatMap(numStyleLink -> styles.findNumberingStyleById(numStyleLink))
                         .flatMap(style -> style.getNumId())
-                        .flatMap(linkedNumId -> findLevel(linkedNumId, level));
+                        .flatMap(linkedNumId -> findLevelWithSeenNumIds(linkedNumId, level, seenNumIds));
                 } else {
                     return lookup(abstractNum.levels, level).map(value -> value.toNumberingLevel());
                 }
diff --git a/src/test/java/org/zwobble/mammoth/tests/docx/NumberingXmlTests.java b/src/test/java/org/zwobble/mammoth/tests/docx/NumberingXmlTests.java
index 676b654..a95e50e 100644
--- a/src/test/java/org/zwobble/mammoth/tests/docx/NumberingXmlTests.java
+++ b/src/test/java/org/zwobble/mammoth/tests/docx/NumberingXmlTests.java
@@ -167,6 +167,27 @@ public class NumberingXmlTests {
         assertEquals(true, numbering.findLevel("201", "0").get().isOrdered());
     }
 
+    @Test
+    public void whenAbstractNumHasSelfRecursiveNumStyleLinkThenLevelIsNotFound() {
+        Numbering numbering = readNumberingXmlElement(
+            element("w:numbering", list(
+                element("w:abstractNum", map("w:abstractNumId", "100"), list(
+                    element("w:numStyleLink", map("w:val", "List1"))
+                )),
+                element("w:num", map("w:numId", "200"), list(
+                    element("w:abstractNumId", map("w:val", "100"))
+                ))
+            )),
+            new Styles(
+                map(),
+                map(),
+                map(),
+                map("List1", new NumberingStyle(Optional.of("200")))
+            )
+        );
+        assertEquals(Optional.empty(), numbering.findLevel("200", "0"));
+    }
+
     // See: 17.9.23 pStyle (Paragraph Style's Associated Numbering Level) in ECMA-376, 4th Edition
     @Test
     public void numberingLevelCanBeFoundByParagraphStyleId() {
-- 
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