fix(markdown): ensure correct parsing of nested lists (#1995)

* fix(markdown): ensure correct parsing of nested lists

Signed-off-by: Cesar Berrospi Ramis <75900930+ceberam@users.noreply.github.com>

* chore: update dependencies in uv.lock file

Signed-off-by: Cesar Berrospi Ramis <75900930+ceberam@users.noreply.github.com>

---------

Signed-off-by: Cesar Berrospi Ramis <75900930+ceberam@users.noreply.github.com>

docling/backend/md_backend.py

@@ -5,7 +5,7 @@ from copy import deepcopy
 from enum import Enum
 from io import BytesIO
 from pathlib import Path
-from typing import List, Literal, Optional, Set, Union
+from typing import Literal, Optional, Union, cast
 
 import marko
 import marko.element
@@ -14,6 +14,7 @@ from docling_core.types.doc import (
     DocItemLabel,
     DoclingDocument,
     DocumentOrigin,
+    ListItem,
     NodeItem,
     TableCell,
     TableData,
@@ -89,7 +90,7 @@ class MarkdownDocumentBackend(DeclarativeDocumentBackend):
     def __init__(self, in_doc: "InputDocument", path_or_stream: Union[BytesIO, Path]):
         super().__init__(in_doc, path_or_stream)
 
-        _log.debug("MD INIT!!!")
+        _log.debug("Starting MarkdownDocumentBackend...")
 
         # Markdown file:
         self.path_or_stream = path_or_stream
@@ -131,7 +132,7 @@ class MarkdownDocumentBackend(DeclarativeDocumentBackend):
             for md_table_row in self.md_table_buffer:
                 _log.debug(md_table_row)
             _log.debug("=== TABLE END ===")
-            tcells: List[TableCell] = []
+            tcells: list[TableCell] = []
             result_table = []
             for n, md_table_row in enumerate(self.md_table_buffer):
                 data = []
@@ -232,11 +233,12 @@ class MarkdownDocumentBackend(DeclarativeDocumentBackend):
         element: marko.element.Element,
         depth: int,
         doc: DoclingDocument,
-        visited: Set[marko.element.Element],
+        visited: set[marko.element.Element],
         creation_stack: list[
             _CreationPayload
         ],  # stack for lazy item creation triggered deep in marko's AST (on RawText)
         list_ordered_flag_by_ref: dict[str, bool],
+        list_last_item_by_ref: dict[str, ListItem],
         parent_item: Optional[NodeItem] = None,
         formatting: Optional[Formatting] = None,
         hyperlink: Optional[Union[AnyUrl, Path]] = None,
@@ -279,7 +281,7 @@ class MarkdownDocumentBackend(DeclarativeDocumentBackend):
 
         elif (
             isinstance(element, marko.block.ListItem)
-            and len(element.children) == 1
+            and len(element.children) > 0
             and isinstance((child := element.children[0]), marko.block.Paragraph)
             and len(child.children) > 0
         ):
@@ -291,7 +293,15 @@ class MarkdownDocumentBackend(DeclarativeDocumentBackend):
                 if parent_item
                 else False
             )
-            if len(child.children) > 1:  # inline group will be created further down
+            non_list_children: list[marko.element.Element] = [
+                item
+                for item in child.children
+                if not isinstance(item, marko.block.ListItem)
+            ]
+            if len(non_list_children) > 1:  # inline group will be created further down
+                parent_ref: Optional[str] = (
+                    parent_item.self_ref if parent_item else None
+                )
                 parent_item = self._create_list_item(
                     doc=doc,
                     parent_item=parent_item,
@@ -300,6 +310,8 @@ class MarkdownDocumentBackend(DeclarativeDocumentBackend):
                     formatting=formatting,
                     hyperlink=hyperlink,
                 )
+                if parent_ref:
+                    list_last_item_by_ref[parent_ref] = cast(ListItem, parent_item)
             else:
                 creation_stack.append(_ListItemCreationPayload(enumerated=enumerated))
 
@@ -334,9 +346,11 @@ class MarkdownDocumentBackend(DeclarativeDocumentBackend):
                 element.dest
             )
 
-        elif isinstance(element, marko.inline.RawText):
-            _log.debug(f" - Paragraph (raw text): {element.children}")
-            snippet_text = element.children.strip()
+        elif isinstance(element, (marko.inline.RawText, marko.inline.Literal)):
+            _log.debug(f" - RawText/Literal: {element.children}")
+            snippet_text = (
+                element.children.strip() if isinstance(element.children, str) else ""
+            )
             # Detect start of the table:
             if "|" in snippet_text or self.in_table:
                 # most likely part of the markdown table
@@ -359,6 +373,7 @@ class MarkdownDocumentBackend(DeclarativeDocumentBackend):
                                 if parent_item
                                 else False
                             )
+                            parent_ref = parent_item.self_ref if parent_item else None
                             parent_item = self._create_list_item(
                                 doc=doc,
                                 parent_item=parent_item,
@@ -367,6 +382,11 @@ class MarkdownDocumentBackend(DeclarativeDocumentBackend):
                                 formatting=formatting,
                                 hyperlink=hyperlink,
                             )
+                            if parent_ref:
+                                list_last_item_by_ref[parent_ref] = cast(
+                                    ListItem, parent_item
+                                )
+
                         elif isinstance(to_create, _HeadingCreationPayload):
                             # not keeping as parent_item as logic for correctly tracking
                             # that not implemented yet (section components not captured
@@ -458,6 +478,17 @@ class MarkdownDocumentBackend(DeclarativeDocumentBackend):
             element, processed_block_types
         ):
             for child in element.children:
+                if (
+                    isinstance(element, marko.block.ListItem)
+                    and isinstance(child, marko.block.List)
+                    and parent_item
+                    and list_last_item_by_ref.get(parent_item.self_ref, None)
+                ):
+                    _log.debug(
+                        f"walking into new List hanging from item of parent list {parent_item.self_ref}"
+                    )
+                    parent_item = list_last_item_by_ref[parent_item.self_ref]
+
                 self._iterate_elements(
                     element=child,
                     depth=depth + 1,
@@ -465,6 +496,7 @@ class MarkdownDocumentBackend(DeclarativeDocumentBackend):
                     visited=visited,
                     creation_stack=creation_stack,
                     list_ordered_flag_by_ref=list_ordered_flag_by_ref,
+                    list_last_item_by_ref=list_last_item_by_ref,
                     parent_item=parent_item,
                     formatting=formatting,
                     hyperlink=hyperlink,
@@ -483,7 +515,7 @@ class MarkdownDocumentBackend(DeclarativeDocumentBackend):
         return False
 
     @classmethod
-    def supported_formats(cls) -> Set[InputFormat]:
+    def supported_formats(cls) -> set[InputFormat]:
         return {InputFormat.MD}
 
     def convert(self) -> DoclingDocument:
@@ -510,6 +542,7 @@ class MarkdownDocumentBackend(DeclarativeDocumentBackend):
                 visited=set(),
                 creation_stack=[],
                 list_ordered_flag_by_ref={},
+                list_last_item_by_ref={},
             )
             self._close_table(doc=doc)  # handle any last hanging table
 
@@ -534,7 +567,6 @@ class MarkdownDocumentBackend(DeclarativeDocumentBackend):
                 ]:
                     html_str = _restore_original_html(txt=html_str, regex=regex)
                 self._html_blocks = 0
-
                 # delegate to HTML backend
                 stream = BytesIO(bytes(html_str, encoding="utf-8"))
                 in_doc = InputDocument(

tests/data/groundtruth/docling_v2/mixed_without_h1.md.md

@@ -3,6 +3,6 @@
 - A. first
     - subitem
 - B. second
-    1. strange
+- 2 . strange
 
 The end!

tests/data/groundtruth/docling_v2/mixed_without_h1.md.yaml

@@ -0,0 +1,139 @@
+body:
+  children:
+  - $ref: '#/texts/0'
+  - $ref: '#/texts/1'
+  - $ref: '#/groups/0'
+  content_layer: body
+  label: unspecified
+  name: _root_
+  self_ref: '#/body'
+form_items: []
+furniture:
+  children: []
+  content_layer: furniture
+  label: unspecified
+  name: _root_
+  self_ref: '#/furniture'
+groups:
+- children:
+  - $ref: '#/texts/2'
+  content_layer: body
+  label: section
+  name: header-1
+  parent:
+    $ref: '#/body'
+  self_ref: '#/groups/0'
+- children:
+  - $ref: '#/texts/3'
+  - $ref: '#/texts/5'
+  - $ref: '#/texts/6'
+  content_layer: body
+  label: list
+  name: list
+  parent:
+    $ref: '#/texts/2'
+  self_ref: '#/groups/1'
+- children:
+  - $ref: '#/texts/4'
+  content_layer: body
+  label: list
+  name: list
+  parent:
+    $ref: '#/texts/3'
+  self_ref: '#/groups/2'
+key_value_items: []
+name: mixed_without_h1
+origin:
+  binary_hash: 7394721163373597328
+  filename: mixed_without_h1.md
+  mimetype: text/html
+pages: {}
+pictures: []
+schema_name: DoclingDocument
+tables: []
+texts:
+- children: []
+  content_layer: furniture
+  label: title
+  orig: mixed_without_h1
+  parent:
+    $ref: '#/body'
+  prov: []
+  self_ref: '#/texts/0'
+  text: mixed_without_h1
+- children: []
+  content_layer: furniture
+  label: text
+  orig: Content before first heading
+  parent:
+    $ref: '#/body'
+  prov: []
+  self_ref: '#/texts/1'
+  text: Content before first heading
+- children:
+  - $ref: '#/groups/1'
+  - $ref: '#/texts/7'
+  content_layer: body
+  label: section_header
+  level: 1
+  orig: Some heading
+  parent:
+    $ref: '#/groups/0'
+  prov: []
+  self_ref: '#/texts/2'
+  text: Some heading
+- children:
+  - $ref: '#/groups/2'
+  content_layer: body
+  enumerated: false
+  label: list_item
+  marker: ''
+  orig: A. first
+  parent:
+    $ref: '#/groups/1'
+  prov: []
+  self_ref: '#/texts/3'
+  text: A. first
+- children: []
+  content_layer: body
+  enumerated: false
+  label: list_item
+  marker: ''
+  orig: subitem
+  parent:
+    $ref: '#/groups/2'
+  prov: []
+  self_ref: '#/texts/4'
+  text: subitem
+- children: []
+  content_layer: body
+  enumerated: false
+  label: list_item
+  marker: ''
+  orig: B. second
+  parent:
+    $ref: '#/groups/1'
+  prov: []
+  self_ref: '#/texts/5'
+  text: B. second
+- children: []
+  content_layer: body
+  enumerated: false
+  label: list_item
+  marker: ''
+  orig: 2 . strange
+  parent:
+    $ref: '#/groups/1'
+  prov: []
+  self_ref: '#/texts/6'
+  text: 2 . strange
+- children: []
+  content_layer: body
+  label: text
+  orig: The end!
+  parent:
+    $ref: '#/texts/2'
+  prov: []
+  self_ref: '#/texts/7'
+  text: The end!
+version: 1.5.0

tests/data/md/mixed_without_h1.md

@@ -7,6 +7,6 @@ Content before first heading
 - A. first
     - subitem
 - B. second
-- 2. strange
+- 2\. strange
 
 The end!

tests/test_backend_markdown.py

@@ -16,7 +16,7 @@ def test_convert_valid():
     relevant_paths = sorted((root_path / "md").rglob("*.md"))
     assert len(relevant_paths) > 0
 
-    yaml_filter = ["inline_and_formatting"]
+    yaml_filter = ["inline_and_formatting", "mixed_without_h1"]
 
     for in_path in relevant_paths:
         md_gt_path = root_path / "groundtruth" / "docling_v2" / f"{in_path.name}.md"
@@ -41,7 +41,6 @@ def test_convert_valid():
                 f.write(f"{act_data}\n")
 
             if in_path.stem in yaml_filter:
-                with open(yaml_gt_path, mode="w", encoding="utf-8") as f:
                 act_doc.save_as_yaml(
                     yaml_gt_path,
                     coord_precision=COORD_PREC,
@@ -54,4 +53,4 @@ def test_convert_valid():
 
             if in_path.stem in yaml_filter:
                 exp_doc = DoclingDocument.load_from_yaml(yaml_gt_path)
-                assert act_doc == exp_doc
+                assert act_doc == exp_doc, f"export to yaml failed on {in_path}"