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fix: HTML serialization of nested lists #359

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Jul 23, 2025
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fix: HTML serialization of nested lists #359

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6d236d8
fix(serializer): the HTML serializer should append nested lists to li…
ceberam Jul 22, 2025
175e5f6
test: address several warning messages
ceberam Jul 22, 2025
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17 changes: 17 additions & 0 deletions docling_core/transforms/serializer/html.py
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Original file line number Diff line number Diff line change
Expand Up @@ -713,6 +713,23 @@ def serialize(
**kwargs,
)

# Append nested list to parent list item:
i = 0
while i < len(parts):
prt = parts[i]
if prt.text.startswith(("<ul>", "<ol>")):
for j in range(i - 1, -1, -1):
if parts[j].text.startswith(("<li>", "<li ")) and parts[
j
].text.endswith("</li>"):
before, _, _ = parts[j].text.rpartition("</li>")
parts[j].text = f"{before}\n{prt.text}\n</li>"
break
if j > -1:
parts.pop(i)
else:
i += 1

# Add all child parts
text_res = "\n".join(
[
Expand Down
15 changes: 10 additions & 5 deletions test/data/doc/constructed_doc.embedded.html.gt
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Original file line number Diff line number Diff line change
Expand Up @@ -135,15 +135,17 @@
<ul>
<li style="list-style-type: '■ ';">list item 1</li>
<li style="list-style-type: '■ ';">list item 2</li>
<li style="list-style-type: '■ ';">list item 3</li>
<li style="list-style-type: '■ ';">list item 3
<ol>
<li>list item 3.a</li>
<li>list item 3.b</li>
<li>list item 3.c</li>
<li>list item 3.c
<ol>
<li>list item 3.c.i</li>
</ol>
</li>
</ol>
</li>
<li style="list-style-type: '■ ';">list item 4</li>
</ul>
<table><caption><div class="caption">This is the caption of table 1.</div></caption><tbody><tr><td rowspan="2">Product</td><td colspan="2">Years</td></tr><tr><td>2016</td><td>2017</td></tr><tr><td>Apple</td><td>49823</td><td>695944</td></tr></tbody></table>
Expand All @@ -158,12 +160,13 @@
</ul>
<ul>
<li style="list-style-type: '■ ';">item 1 of neighboring list</li>
<li style="list-style-type: '■ ';">item 2 of neighboring list</li>
<li style="list-style-type: '■ ';">item 2 of neighboring list
<ul>
<li style="list-style-type: '□ ';">item 1 of sub list</li>
<li style="list-style-type: '□ ';"><span class='inline-group'>Here a code snippet: <code>print("Hello world")</code> (to be displayed inline)</span></li>
<li style="list-style-type: '□ ';"><span class='inline-group'>Here a formula: <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><mi>E</mi><mo>&#x0003D;</mo><mi>m</mi><msup><mi>c</mi><mn>2</mn></msup></mrow><annotation encoding="TeX">E=mc^2</annotation></math> (to be displayed inline)</span></li>
</ul>
</li>
</ul>
<p>Here a code block:</p>
<pre><code>print("Hello world")</code></pre>
Expand All @@ -185,16 +188,18 @@
<ol>
<li style="list-style-type: '(i) ';">Item 1 in A</li>
<li style="list-style-type: '(ii) ';">Item 2 in A</li>
<li style="list-style-type: '(iii) ';">Item 3 in A</li>
<li style="list-style-type: '(iii) ';">Item 3 in A
<ol>
<li>Item 1 in B</li>
<li style="list-style-type: '42. ';">Item 2 in B</li>
<li style="list-style-type: '42. ';">Item 2 in B
<ol>
<li>Item 1 in C</li>
<li>Item 2 in C</li>
</ol>
</li>
<li>Item 3 in B</li>
</ol>
</li>
<li style="list-style-type: '(iv) ';">Item 4 in A</li>
</ol>
<ul>
Expand Down
15 changes: 10 additions & 5 deletions test/data/doc/constructed_doc.html
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Original file line number Diff line number Diff line change
Expand Up @@ -134,15 +134,17 @@ <h2>1. Introduction</h2>
<ul>
<li>list item 1</li>
<li>list item 2</li>
<li>list item 3</li>
<li>list item 3
<ol>
<li>list item 3.a</li>
<li>list item 3.b</li>
<li>list item 3.c</li>
<li>list item 3.c
<ol>
<li>list item 3.c.i</li>
</ol>
</li>
</ol>
</li>
<li>list item 4</li>
</ul>
<table><caption>This is the caption of table 1.</caption><tbody><tr><td rowspan="2">Product</td><td colspan="2">Years</td></tr><tr><td>2016</td><td>2017</td></tr><tr><td>Apple</td><td>49823</td><td>695944</td></tr></tbody></table>
Expand All @@ -157,12 +159,13 @@ <h2>1. Introduction</h2>
</ul>
<ul>
<li>item 1 of neighboring list</li>
<li>item 2 of neighboring list</li>
<li>item 2 of neighboring list
<ul>
<li>item 1 of sub list</li>
<li><span class='inline-group'>Here a code snippet: <code>&lt;p&gt;Hello world&lt;/p&gt;</code> (to be displayed inline)</span></li>
<li><span class='inline-group'>Here a formula: <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><mi>E</mi><mo>&#x0003D;</mo><mi>m</mi><msup><mi>c</mi><mn>2</mn></msup></mrow><annotation encoding="TeX">E=mc^2</annotation></math> (to be displayed inline)</span></li>
</ul>
</li>
</ul>
<p>Here a code block:</p>
<pre><code>print("Hello world")</code></pre>
Expand All @@ -186,16 +189,18 @@ <h2>1. Introduction</h2>
<ol>
<li>Item 1 in A</li>
<li>Item 2 in A</li>
<li>Item 3 in A</li>
<li>Item 3 in A
<ol>
<li>Item 1 in B</li>
<li>Item 2 in B</li>
<li>Item 2 in B
<ol>
<li>Item 1 in C</li>
<li>Item 2 in C</li>
</ol>
</li>
<li>Item 3 in B</li>
</ol>
</li>
<li>Item 4 in A</li>
</ol>
<p>The end.</p>
Expand Down
15 changes: 10 additions & 5 deletions test/data/doc/constructed_doc.placeholder.html.gt
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Original file line number Diff line number Diff line change
Expand Up @@ -135,15 +135,17 @@
<ul>
<li style="list-style-type: '■ ';">list item 1</li>
<li style="list-style-type: '■ ';">list item 2</li>
<li style="list-style-type: '■ ';">list item 3</li>
<li style="list-style-type: '■ ';">list item 3
<ol>
<li>list item 3.a</li>
<li>list item 3.b</li>
<li>list item 3.c</li>
<li>list item 3.c
<ol>
<li>list item 3.c.i</li>
</ol>
</li>
</ol>
</li>
<li style="list-style-type: '■ ';">list item 4</li>
</ul>
<table><caption><div class="caption">This is the caption of table 1.</div></caption><tbody><tr><td rowspan="2">Product</td><td colspan="2">Years</td></tr><tr><td>2016</td><td>2017</td></tr><tr><td>Apple</td><td>49823</td><td>695944</td></tr></tbody></table>
Expand All @@ -158,12 +160,13 @@
</ul>
<ul>
<li style="list-style-type: '■ ';">item 1 of neighboring list</li>
<li style="list-style-type: '■ ';">item 2 of neighboring list</li>
<li style="list-style-type: '■ ';">item 2 of neighboring list
<ul>
<li style="list-style-type: '□ ';">item 1 of sub list</li>
<li style="list-style-type: '□ ';"><span class='inline-group'>Here a code snippet: <code>print("Hello world")</code> (to be displayed inline)</span></li>
<li style="list-style-type: '□ ';"><span class='inline-group'>Here a formula: <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><mi>E</mi><mo>&#x0003D;</mo><mi>m</mi><msup><mi>c</mi><mn>2</mn></msup></mrow><annotation encoding="TeX">E=mc^2</annotation></math> (to be displayed inline)</span></li>
</ul>
</li>
</ul>
<p>Here a code block:</p>
<pre><code>print("Hello world")</code></pre>
Expand All @@ -185,16 +188,18 @@
<ol>
<li style="list-style-type: '(i) ';">Item 1 in A</li>
<li style="list-style-type: '(ii) ';">Item 2 in A</li>
<li style="list-style-type: '(iii) ';">Item 3 in A</li>
<li style="list-style-type: '(iii) ';">Item 3 in A
<ol>
<li>Item 1 in B</li>
<li style="list-style-type: '42. ';">Item 2 in B</li>
<li style="list-style-type: '42. ';">Item 2 in B
<ol>
<li>Item 1 in C</li>
<li>Item 2 in C</li>
</ol>
</li>
<li>Item 3 in B</li>
</ol>
</li>
<li style="list-style-type: '(iv) ';">Item 4 in A</li>
</ol>
<ul>
Expand Down
15 changes: 10 additions & 5 deletions test/data/doc/constructed_doc.referenced.html.gt
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Original file line number Diff line number Diff line change
Expand Up @@ -135,15 +135,17 @@
<ul>
<li style="list-style-type: '■ ';">list item 1</li>
<li style="list-style-type: '■ ';">list item 2</li>
<li style="list-style-type: '■ ';">list item 3</li>
<li style="list-style-type: '■ ';">list item 3
<ol>
<li>list item 3.a</li>
<li>list item 3.b</li>
<li>list item 3.c</li>
<li>list item 3.c
<ol>
<li>list item 3.c.i</li>
</ol>
</li>
</ol>
</li>
<li style="list-style-type: '■ ';">list item 4</li>
</ul>
<table><caption><div class="caption">This is the caption of table 1.</div></caption><tbody><tr><td rowspan="2">Product</td><td colspan="2">Years</td></tr><tr><td>2016</td><td>2017</td></tr><tr><td>Apple</td><td>49823</td><td>695944</td></tr></tbody></table>
Expand All @@ -158,12 +160,13 @@
</ul>
<ul>
<li style="list-style-type: '■ ';">item 1 of neighboring list</li>
<li style="list-style-type: '■ ';">item 2 of neighboring list</li>
<li style="list-style-type: '■ ';">item 2 of neighboring list
<ul>
<li style="list-style-type: '□ ';">item 1 of sub list</li>
<li style="list-style-type: '□ ';"><span class='inline-group'>Here a code snippet: <code>print("Hello world")</code> (to be displayed inline)</span></li>
<li style="list-style-type: '□ ';"><span class='inline-group'>Here a formula: <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><mi>E</mi><mo>&#x0003D;</mo><mi>m</mi><msup><mi>c</mi><mn>2</mn></msup></mrow><annotation encoding="TeX">E=mc^2</annotation></math> (to be displayed inline)</span></li>
</ul>
</li>
</ul>
<p>Here a code block:</p>
<pre><code>print("Hello world")</code></pre>
Expand All @@ -185,16 +188,18 @@
<ol>
<li style="list-style-type: '(i) ';">Item 1 in A</li>
<li style="list-style-type: '(ii) ';">Item 2 in A</li>
<li style="list-style-type: '(iii) ';">Item 3 in A</li>
<li style="list-style-type: '(iii) ';">Item 3 in A
<ol>
<li>Item 1 in B</li>
<li style="list-style-type: '42. ';">Item 2 in B</li>
<li style="list-style-type: '42. ';">Item 2 in B
<ol>
<li>Item 1 in C</li>
<li>Item 2 in C</li>
</ol>
</li>
<li>Item 3 in B</li>
</ol>
</li>
<li style="list-style-type: '(iv) ';">Item 4 in A</li>
</ol>
<ul>
Expand Down
15 changes: 10 additions & 5 deletions test/data/doc/constructed_document.yaml.html
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Original file line number Diff line number Diff line change
Expand Up @@ -135,15 +135,17 @@ <h2>1. Introduction</h2>
<ul>
<li style="list-style-type: '■ ';">list item 1</li>
<li style="list-style-type: '■ ';">list item 2</li>
<li style="list-style-type: '■ ';">list item 3</li>
<li style="list-style-type: '■ ';">list item 3
<ol>
<li>list item 3.a</li>
<li>list item 3.b</li>
<li>list item 3.c</li>
<li>list item 3.c
<ol>
<li>list item 3.c.i</li>
</ol>
</li>
</ol>
</li>
<li style="list-style-type: '■ ';">list item 4</li>
</ul>
<table><caption><div class="caption">This is the caption of table 1.</div></caption><tbody><tr><td rowspan="2">Product</td><td colspan="2">Years</td></tr><tr><td>2016</td><td>2017</td></tr><tr><td>Apple</td><td>49823</td><td>695944</td></tr></tbody></table>
Expand All @@ -158,12 +160,13 @@ <h2>1. Introduction</h2>
</ul>
<ul>
<li style="list-style-type: '■ ';">item 1 of neighboring list</li>
<li style="list-style-type: '■ ';">item 2 of neighboring list</li>
<li style="list-style-type: '■ ';">item 2 of neighboring list
<ul>
<li style="list-style-type: '□ ';">item 1 of sub list</li>
<li style="list-style-type: '□ ';"><span class='inline-group'>Here a code snippet: <code>print("Hello world")</code> (to be displayed inline)</span></li>
<li style="list-style-type: '□ ';"><span class='inline-group'>Here a formula: <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><mi>E</mi><mo>&#x0003D;</mo><mi>m</mi><msup><mi>c</mi><mn>2</mn></msup></mrow><annotation encoding="TeX">E=mc^2</annotation></math> (to be displayed inline)</span></li>
</ul>
</li>
</ul>
<p>Here a code block:</p>
<pre><code>print("Hello world")</code></pre>
Expand All @@ -185,16 +188,18 @@ <h2>1. Introduction</h2>
<ol>
<li style="list-style-type: '(i) ';">Item 1 in A</li>
<li style="list-style-type: '(ii) ';">Item 2 in A</li>
<li style="list-style-type: '(iii) ';">Item 3 in A</li>
<li style="list-style-type: '(iii) ';">Item 3 in A
<ol>
<li>Item 1 in B</li>
<li style="list-style-type: '42. ';">Item 2 in B</li>
<li style="list-style-type: '42. ';">Item 2 in B
<ol>
<li>Item 1 in C</li>
<li>Item 2 in C</li>
</ol>
</li>
<li>Item 3 in B</li>
</ol>
</li>
<li style="list-style-type: '(iv) ';">Item 4 in A</li>
</ol>
<ul>
Expand Down
15 changes: 10 additions & 5 deletions test/data/doc/constructed_orig_false.gt.html
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Original file line number Diff line number Diff line change
Expand Up @@ -135,15 +135,17 @@ <h2>1. Introduction</h2>
<ul>
<li>list item 1</li>
<li>list item 2</li>
<li>list item 3</li>
<li>list item 3
<ol>
<li>list item 3.a</li>
<li>list item 3.b</li>
<li>list item 3.c</li>
<li>list item 3.c
<ol>
<li>list item 3.c.i</li>
</ol>
</li>
</ol>
</li>
<li>list item 4</li>
</ul>
<table><caption><div class="caption">This is the caption of table 1.</div></caption><tbody><tr><td rowspan="2">Product</td><td colspan="2">Years</td></tr><tr><td>2016</td><td>2017</td></tr><tr><td>Apple</td><td>49823</td><td>695944</td></tr></tbody></table>
Expand All @@ -158,12 +160,13 @@ <h2>1. Introduction</h2>
</ul>
<ul>
<li>item 1 of neighboring list</li>
<li>item 2 of neighboring list</li>
<li>item 2 of neighboring list
<ul>
<li>item 1 of sub list</li>
<li><span class='inline-group'>Here a code snippet: <code>print("Hello world")</code> (to be displayed inline)</span></li>
<li><span class='inline-group'>Here a formula: <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><mi>E</mi><mo>&#x0003D;</mo><mi>m</mi><msup><mi>c</mi><mn>2</mn></msup></mrow><annotation encoding="TeX">E=mc^2</annotation></math> (to be displayed inline)</span></li>
</ul>
</li>
</ul>
<p>Here a code block:</p>
<pre><code>print("Hello world")</code></pre>
Expand All @@ -185,16 +188,18 @@ <h2>1. Introduction</h2>
<ol>
<li>Item 1 in A</li>
<li>Item 2 in A</li>
<li>Item 3 in A</li>
<li>Item 3 in A
<ol>
<li>Item 1 in B</li>
<li>Item 2 in B</li>
<li>Item 2 in B
<ol>
<li>Item 1 in C</li>
<li>Item 2 in C</li>
</ol>
</li>
<li>Item 3 in B</li>
</ol>
</li>
<li>Item 4 in A</li>
</ol>
<ul>
Expand Down
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