fix: fix page breaking in case page starts with group (#253)

Signed-off-by: Panos Vagenas <[email protected]>

Author: vagenas

docling_core/experimental/serializer/common.py

@@ -69,7 +69,9 @@ def _iterate_items(
     node: Optional[NodeItem] = None,
     traverse_pictures: bool = False,
     add_page_breaks: bool = False,
+    visited: Optional[set[str]] = None,
 ):
+    my_visited: set[str] = visited if visited is not None else set()
     prev_page_nr: Optional[int] = None
     page_break_i = 0
     for item, _ in doc.iterate_items(
@@ -78,10 +80,33 @@ def _iterate_items(
         included_content_layers=layers,
         traverse_pictures=traverse_pictures,
     ):
-        if isinstance(item, DocItem):
-            if item.prov:
+        if add_page_breaks:
+            if (
+                isinstance(item, (UnorderedList, OrderedList, InlineGroup))
+                and item.self_ref not in my_visited
+            ):
+                # if group starts with new page, yield page break before group node
+                my_visited.add(item.self_ref)
+                for it in _iterate_items(
+                    doc=doc,
+                    layers=layers,
+                    node=item,
+                    traverse_pictures=traverse_pictures,
+                    add_page_breaks=add_page_breaks,
+                    visited=my_visited,
+                ):
+                    if isinstance(it, DocItem) and it.prov:
+                        page_no = it.prov[0].page_no
+                        if prev_page_nr is not None and page_no > prev_page_nr:
+                            yield _PageBreakNode(
+                                self_ref=f"#/pb/{page_break_i}",
+                                prev_page=prev_page_nr,
+                                next_page=page_no,
+                            )
+                        break
+            elif isinstance(item, DocItem) and item.prov:
                 page_no = item.prov[0].page_no
-                if add_page_breaks and (prev_page_nr is None or page_no > prev_page_nr):
+                if prev_page_nr is None or page_no > prev_page_nr:
                     if prev_page_nr is not None:  # close previous range
                         yield _PageBreakNode(
                             self_ref=f"#/pb/{page_break_i}",

test/data/doc/activities.gt.html

@@ -147,6 +147,11 @@ <h2>Let's swim!</h2>
 <li>-Yet another one</li>
 <li>-Stopping it here</li>
 </ul>
+<p>Some text.</p>
+<ul>
+<li>-Starting the next page with a list item.</li>
+<li>-Second item.</li>
+</ul>
 </div>
 </body>
 </html>

test/data/doc/activities.gt.md

@@ -26,3 +26,10 @@ Hmm, what else…
 <!-- page break -->
 - -Yet another one
 - -Stopping it here
+
+Some text.
+
+<!-- page break -->
+
+- -Starting the next page with a list item.
+- -Second item.