feat(markdown): add footnote serialization support

docling_core/transforms/serializer/markdown.py

@@ -566,6 +566,13 @@ def serialize(
             if table_text:
                 res_parts.append(create_ser_result(text=table_text, span_source=item))
 
+        ftn_res = doc_serializer.serialize_footnotes(
+            item=item,
+            **kwargs,
+        )
+        if ftn_res.text:
+            res_parts.append(ftn_res)
+
         text_res = "\n\n".join([r.text for r in res_parts])
 
         return create_ser_result(text=text_res, span_source=res_parts)
@@ -626,6 +633,14 @@ def serialize(
                 md_table_content = temp_table.export_to_markdown(temp_doc)
                 if len(md_table_content) > 0:
                     res_parts.append(create_ser_result(text=md_table_content, span_source=item))
+
+        ftn_res = doc_serializer.serialize_footnotes(
+            item=item,
+            **kwargs,
+        )
+        if ftn_res.text:
+            res_parts.append(ftn_res)
+
         text_res = "\n\n".join([r.text for r in res_parts if r.text])
 
         return create_ser_result(text=text_res, span_source=res_parts)
@@ -842,6 +857,34 @@ class MarkdownDocSerializer(DocSerializer):
 
     params: MarkdownParams = MarkdownParams()
 
+    @override
+    def serialize_footnotes(
+        self,
+        item: FloatingItem,
+        **kwargs: Any,
+    ) -> SerializationResult:
+        params: MarkdownParams = self.params.merge_with_patch(patch=kwargs)
+        results: list[SerializationResult] = []
+        if DocItemLabel.FOOTNOTE in params.labels:
+            results = []
+            for footnote in item.footnotes:
+                if isinstance(ftn := footnote.resolve(self.doc), TextItem):
+                    parts = ftn.text.split(" ", 1)
+
+                    if len(parts) == 2:
+                        formatted_text = f"[^{parts[0]}]: {parts[1]}\n"
+                    else:
+                        formatted_text = f"[^{parts[0]}]:\n"
+
+                    results.append(create_ser_result(text=formatted_text, span_source=ftn))
+
+            text_res = "".join([r.text for r in results])
+
+        else:
+            text_res = ""
+
+        return create_ser_result(text=text_res, span_source=results)
+
     @override
     def serialize_bold(self, text: str, **kwargs: Any):
         """Apply Markdown-specific bold serialization."""

test/test_markdown_footnotes.py

@@ -0,0 +1,137 @@
+from docling_core.transforms.serializer.markdown import MarkdownDocSerializer
+from docling_core.types.doc import DocItemLabel, DoclingDocument, TableCell, TableData
+from docling_core.types.doc.document import (
+    CodeItem,
+    FieldHeadingItem,
+    FieldValueItem,
+    FormulaItem,
+    ListItem,
+    SectionHeaderItem,
+    TextItem,
+    TitleItem,
+)
+
+# Mock footnotes for pre-serialization
+numericFtnMock = "1 Note about data"
+wordFtnMock = "ID Note about data"
+idOnlyFtnMock = "ID"
+
+# Mock footnotes for post-serialization
+numericFtnSerialized = "[^1]: Note about data\n"
+wordFtnSerialized = "[^ID]: Note about data\n"
+idOnlyFtnSerialized = "[^ID]:\n"
+
+
+def test_table_with_footnotes_markdown():
+    doc = DoclingDocument(name="test")
+
+    table = doc.add_table(data=TableData())
+
+    # Test three types of footnotes on table
+    footnote1: TextItem = doc.add_text(label=DocItemLabel.FOOTNOTE, text=numericFtnMock)
+    footnote2: TextItem = doc.add_text(label=DocItemLabel.FOOTNOTE, text=wordFtnMock)
+    footnote3: TextItem = doc.add_text(label=DocItemLabel.FOOTNOTE, text=idOnlyFtnMock)
+
+    table.footnotes.append(footnote1.get_ref())
+    table.footnotes.append(footnote2.get_ref())
+    table.footnotes.append(footnote3.get_ref())
+
+    serializer = MarkdownDocSerializer(doc=doc)
+
+    result = serializer.serialize(item=table)
+
+    # Verify serialization result has formatted footnotes
+    assert numericFtnSerialized in result.text
+    assert wordFtnSerialized in result.text
+    assert idOnlyFtnSerialized in result.text
+
+
+def test_picture_with_footnotes_markdown():
+    doc = DoclingDocument(name="test")
+
+    picture = doc.add_picture()
+
+    # Test one footnote on picture
+    footnote1: TextItem = doc.add_text(label=DocItemLabel.FOOTNOTE, text=numericFtnMock)
+
+    picture.footnotes.append(footnote1.get_ref())
+
+    serializer = MarkdownDocSerializer(doc=doc)
+    result = serializer.serialize(item=picture)
+
+    # Verify serialization result has formatted footnote
+    assert numericFtnSerialized in result.text
+
+
+def test_table_export_to_markdown_with_footnotes():
+    doc = DoclingDocument(name="test")
+
+    # Create a table
+    table_data = TableData(
+        num_rows=2,
+        num_cols=2,
+        table_cells=[
+            TableCell(
+                text="Header 1",
+                row_span=1,
+                col_span=1,
+                start_row_offset_idx=0,
+                end_row_offset_idx=0,
+                start_col_offset_idx=0,
+                end_col_offset_idx=0,
+                column_header=True,
+            ),
+            TableCell(
+                text="Header 2",
+                row_span=1,
+                col_span=1,
+                start_row_offset_idx=0,
+                end_row_offset_idx=0,
+                start_col_offset_idx=1,
+                end_col_offset_idx=1,
+                column_header=True,
+            ),
+            TableCell(
+                text="Data 1",
+                row_span=1,
+                col_span=1,
+                start_row_offset_idx=1,
+                end_row_offset_idx=1,
+                start_col_offset_idx=0,
+                end_col_offset_idx=0,
+            ),
+            TableCell(
+                text="Data 2",
+                row_span=1,
+                col_span=1,
+                start_row_offset_idx=1,
+                end_row_offset_idx=1,
+                start_col_offset_idx=1,
+                end_col_offset_idx=1,
+            ),
+        ],
+    )
+
+    table = doc.add_table(data=table_data)
+
+    caption = doc.add_text(label=DocItemLabel.CAPTION, text="Table 1: Sample Data")
+    table.captions.append(caption.get_ref())
+
+    # Test one footnote on picture
+    footnote1 = doc.add_text(label=DocItemLabel.FOOTNOTE, text=numericFtnMock)
+
+    table.footnotes.append(footnote1.get_ref())
+
+    markdown = table.export_to_markdown(doc)
+
+    # Test Table is in exported markdown
+    assert "Table 1: Sample Data" in markdown
+
+    # Test Footnote is in exported markdown
+    assert numericFtnSerialized in markdown
+
+
+if __name__ == "__main__":
+    test_table_with_footnotes_markdown()
+    test_picture_with_footnotes_markdown()
+    test_table_export_to_markdown_with_footnotes()