Strip TOC elements from article summaries

Automatically remove table of contents divs and toc-backref anchor links
from article summaries when displayed outside full article context
(e.g., on homepage, in RSS feeds).

ReStructuredText automatically generates anchor links in section headings
when a table of contents directive is present. These anchors work perfectly
on full article pages, but become broken links when article summaries appear
on homepage or in feeds - the anchor targets don't exist in that context.

This change adds a strip_toc_elements_from_html() function in pelican/utils.py
that uses regex to remove:
- TOC div blocks (<div class="contents">...</div>) containing broken navigation
- toc-backref anchor links from headings while preserving heading text

Both removals are necessary since TOC anchor targets don't exist in summary context.

The function is called automatically in Content.get_summary() so all
summaries are cleaned without requiring configuration or template changes.

Includes comprehensive unit tests covering various TOC formats, edge cases,
and case-insensitive matching.

pelican/contents.py

@@ -27,6 +27,7 @@ from pelican.utils import (
     sanitised_join,
     set_date_tzinfo,
     slugify,
+    strip_toc_elements_from_html,
     truncate_html_paragraphs,
     truncate_html_words,
 )
@@ -446,13 +447,19 @@ class Content:
             content = truncate_html_paragraphs(self.content, max_paragraphs)
 
         if self.settings["SUMMARY_MAX_LENGTH"] is None:
-            return content
+            summary = content
+        else:
+            summary = truncate_html_words(
+                content,
+                self.settings["SUMMARY_MAX_LENGTH"],
+                self.settings["SUMMARY_END_SUFFIX"],
+            )
 
-        return truncate_html_words(
-            content,
-            self.settings["SUMMARY_MAX_LENGTH"],
-            self.settings["SUMMARY_END_SUFFIX"],
-        )
+        # Strip TOC elements that would contain broken links in summary context
+        # TOC anchors only work in full article view, not in summaries/excerpts
+        summary = strip_toc_elements_from_html(summary)
+
+        return summary
 
     @property
     def summary(self) -> str:

pelican/tests/test_utils.py

@@ -420,6 +420,60 @@ class TestUtils(LoggedTestCase):
         self.assertEqual(utils.truncate_html_paragraphs(three, 3), three)
         self.assertEqual(utils.truncate_html_paragraphs(three, 4), three)
 
+    def test_strip_toc_elements_from_html(self):
+        # Test removing TOC div with various class names
+        html_with_toc = (
+            '<div class="contents topic" id="table-of-contents">'
+            '<p class="topic-title">Table of Contents</p>'
+            '<ul><li><a href="#section1">Section 1</a></li></ul>'
+            "</div>"
+            "<p>Some content here</p>"
+        )
+        result = utils.strip_toc_elements_from_html(html_with_toc)
+        self.assertNotIn('<div class="contents', result)
+        self.assertIn("<p>Some content here</p>", result)
+
+        # Test removing toc-backref anchors while preserving heading text
+        html_with_backref = (
+            '<h2><a class="toc-backref" href="#id1">Section Heading</a></h2>'
+            "<p>Some content</p>"
+        )
+        result = utils.strip_toc_elements_from_html(html_with_backref)
+        self.assertNotIn("toc-backref", result)
+        self.assertNotIn("<a class=", result)
+        self.assertIn("Section Heading", result)
+        self.assertIn("<h2>Section Heading</h2>", result)
+
+        # Test combined - remove both TOC div and backrefs
+        html_combined = (
+            '<div class="contents">'
+            "<p>TOC here</p>"
+            "</div>"
+            '<h2><a class="toc-backref" href="#id1">the design</a></h2>'
+            "<p>Article content</p>"
+            '<h2><a class="toc-backref" href="#id2">key features</a></h2>'
+            "<p>More content</p>"
+        )
+        result = utils.strip_toc_elements_from_html(html_combined)
+        self.assertNotIn('<div class="contents', result)
+        self.assertNotIn("toc-backref", result)
+        self.assertIn("the design", result)
+        self.assertIn("key features", result)
+        self.assertIn("<p>Article content</p>", result)
+
+        # Test empty input
+        self.assertEqual(utils.strip_toc_elements_from_html(""), "")
+
+        # Test HTML without TOC elements (should be unchanged)
+        plain_html = "<p>Just some plain content</p>"
+        self.assertEqual(utils.strip_toc_elements_from_html(plain_html), plain_html)
+
+        # Test case-insensitive matching
+        html_mixed_case = '<div CLASS="CONTENTS"><p>TOC</p></div><p>Content</p>'
+        result = utils.strip_toc_elements_from_html(html_mixed_case)
+        self.assertNotIn("CONTENTS", result)
+        self.assertIn("<p>Content</p>", result)
+
     def test_process_translations(self):
         fr_articles = []
         en_articles = []

pelican/utils.py

@@ -643,6 +643,37 @@ def truncate_html_paragraphs(s, count):
     return "".join(paragraphs)
 
 
+def strip_toc_elements_from_html(html: str) -> str:
+    """Strip table of contents elements from HTML summaries.
+
+    Removes TOC divs (with broken navigation links) and toc-backref anchor
+    links from headings. Both are necessary since TOC anchor targets don't
+    exist when summaries are displayed outside full article context
+    (e.g., homepage, RSS feeds).
+
+    :param html: HTML content to process
+    :return: Cleaned HTML with TOC elements removed
+    """
+    # Remove the entire <div class="contents"> ... </div> block
+    html = re.sub(
+        r'<div\s+class="contents[^"]*"[^>]*>.*?</div>',
+        "",
+        html,
+        flags=re.DOTALL | re.IGNORECASE,
+    )
+
+    # Remove anchor links from headings (e.g., <a class="toc-backref" href="#id1">text</a>)
+    # These links point to anchors that don't exist in summary context
+    html = re.sub(
+        r'<a[^>]*class="[^"]*toc-backref[^"]*"[^>]*>(.*?)</a>',
+        r"\1",
+        html,
+        flags=re.DOTALL | re.IGNORECASE,
+    )
+
+    return html
+
+
 def process_translations(
     content_list: list[Content],
     translation_id: str | Collection[str] | None = None,