fix(markdown): add support for HTML content (#855)

Signed-off-by: Panos Vagenas <35837085+vagenas@users.noreply.github.com>

docling/backend/md_backend.py

@@ -24,11 +24,16 @@ from docling_core.types.doc import (
 from marko import Markdown
 
 from docling.backend.abstract_backend import DeclarativeDocumentBackend
+from docling.backend.html_backend import HTMLDocumentBackend
 from docling.datamodel.base_models import InputFormat
 from docling.datamodel.document import InputDocument
 
 _log = logging.getLogger(__name__)
 
+_MARKER_BODY = "DOCLING_DOC_MD_HTML_EXPORT"
+_START_MARKER = f"#_#_{_MARKER_BODY}_START_#_#"
+_STOP_MARKER = f"#_#_{_MARKER_BODY}_STOP_#_#"
+
 
 class MarkdownDocumentBackend(DeclarativeDocumentBackend):
     def shorten_underscore_sequences(self, markdown_text: str, max_length: int = 10):
@@ -67,6 +72,7 @@ class MarkdownDocumentBackend(DeclarativeDocumentBackend):
         self.in_table = False
         self.md_table_buffer: list[str] = []
         self.inline_texts: list[str] = []
+        self._html_blocks: int = 0
 
         try:
             if isinstance(self.path_or_stream, BytesIO):
@@ -295,16 +301,18 @@ class MarkdownDocumentBackend(DeclarativeDocumentBackend):
                 self.md_table_buffer.append("")
 
         elif isinstance(element, marko.block.HTMLBlock):
+            self._html_blocks += 1
             self.process_inline_text(parent_element, doc)
             self.close_table(doc)
             _log.debug("HTML Block: {}".format(element))
             if (
-                len(element.children) > 0
+                len(element.body) > 0
             ):  # If Marko doesn't return any content for HTML block, skip it
-                snippet_text = str(element.children).strip()
-                doc.add_text(
-                    label=DocItemLabel.CODE, parent=parent_element, text=snippet_text
-                )
+                html_block = element.body.strip()
+
+                # wrap in markers to enable post-processing in convert()
+                text_to_add = f"{_START_MARKER}{html_block}{_STOP_MARKER}"
+                doc.add_code(parent=parent_element, text=text_to_add)
         else:
             if not isinstance(element, str):
                 self.close_table(doc)
@@ -360,6 +368,42 @@ class MarkdownDocumentBackend(DeclarativeDocumentBackend):
             # Start iterating from the root of the AST
             self.iterate_elements(parsed_ast, 0, doc, None)
             self.process_inline_text(None, doc)  # handle last hanging inline text
+
+            # if HTML blocks were detected, export to HTML and delegate to HTML backend
+            if self._html_blocks > 0:
+
+                # export to HTML
+                html_backend_cls = HTMLDocumentBackend
+                html_str = doc.export_to_html()
+
+                def _restore_original_html(txt, regex):
+                    _txt, count = re.subn(regex, "", txt)
+                    if count != self._html_blocks:
+                        raise RuntimeError(
+                            "An internal error has occurred during Markdown conversion."
+                        )
+                    return _txt
+
+                # restore original HTML by removing previouly added markers
+                for regex in [
+                    rf"<pre>\s*<code>\s*{_START_MARKER}",
+                    rf"{_STOP_MARKER}\s*</code>\s*</pre>",
+                ]:
+                    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(
+                    path_or_stream=stream,
+                    format=InputFormat.HTML,
+                    backend=html_backend_cls,
+                    filename=self.file.name,
+                )
+                html_backend_obj = html_backend_cls(
+                    in_doc=in_doc, path_or_stream=stream
+                )
+                doc = html_backend_obj.convert()
         else:
             raise RuntimeError(
                 f"Cannot convert md with {self.document_hash} because the backend failed to init."

tests/data/groundtruth/docling_v2/mixed.md.md

@@ -0,0 +1,25 @@
+# Title
+
+Some text
+
+## Famous ducks
+
+Here is a table:
+
+| Character      | Name in German   | Name in French   | Name in Italian   |
+|----------------|------------------|------------------|-------------------|
+| Scrooge McDuck | Dagobert Duck    | Balthazar Picsou | Paperone          |
+| Huey           | Tick             | Riri             | Qui               |
+| Dewey          | Trick            | Fifi             | Quo               |
+| Louie          | Track            | Loulou           | Qua               |
+
+And here is more HTML:
+
+Some paragraph.
+
+Now a div — almost there...
+
+- foo
+- bar
+
+The end!

tests/data/groundtruth/docling_v2/word_tables.docx.html

@@ -53,6 +53,20 @@
     table tr:nth-child(even) td{
     background-color: LightGray;
     }
+    math annotation {
+    display: none;
+    }
+    .formula-not-decoded {
+    background: repeating-linear-gradient(
+    45deg, /* Angle of the stripes */
+    LightGray, /* First color */
+    LightGray 10px, /* Length of the first color */
+    White 10px, /* Second color */
+    White 20px /* Length of the second color */
+    );
+    margin: 0;
+    text-align: center;
+    }
     </style>
     </head>
 <h2>Test with tables</h2>

tests/data/md/mixed.md

@@ -0,0 +1,54 @@
+# Title
+
+Some text
+
+## Famous ducks
+
+Here is a table:
+
+<table>
+  <tr>
+    <th>Character</th>
+    <th>Name in German</th>
+    <th>Name in French</th>
+    <th>Name in Italian</th>
+  </tr>
+  <tr>
+    <td>Scrooge McDuck</td>
+    <td>Dagobert Duck</td>
+    <td>Balthazar Picsou</td>
+    <td>Paperone</td>
+  </tr>
+  <tr>
+    <td>Huey</td>
+    <td>Tick</td>
+    <td>Riri</td>
+    <td>Qui</td>
+  </tr>
+  <tr>
+    <td>Dewey</td>
+    <td>Trick</td>
+    <td>Fifi</td>
+    <td>Quo</td>
+  </tr>
+  <tr>
+    <td>Louie</td>
+    <td>Track</td>
+    <td>Loulou</td>
+    <td>Qua</td>
+  </tr>
+</table>
+
+And here is more HTML:
+
+<p>Some paragraph.</p>
+
+<div>
+    <p>Now a div — almost there...</p>
+    <ul>
+        <li>foo</li>
+        <li>bar</li>
+    </ul>
+</div>
+
+The end!