docs/qapidoc: fix nested parsing under untagged sections

Sphinx does not like sections without titles, because it wants to
convert every section into a reference. When there is no title, it
struggles to do this and transforms the tree inproperly.

Depending on the rST used, this may result in an assertion error deep in
the docutils HTMLWriter.

(Observed when using ".. admonition:: Notes" under such a section - When
this is transformed with its own <title> element, Sphinx is fooled into
believing this title belongs to the section and incorrect mutates the
docutils tree, leading to errors during rendering time.)

When parsing an untagged section (free paragraphs), skip making a hollow
section and instead append the parse results to the prior section.

Many Bothans died to bring us this information.

The resulting output changes are basically invisible.

Signed-off-by: John Snow <jsnow@redhat.com>
Acked-by: Markus Armbruster <armbru@redhat.com>
Message-ID: <20240626222128.406106-8-jsnow@redhat.com>
[Mention output changes in commit message]
Signed-off-by: Markus Armbruster <armbru@redhat.com>

1 files changed, 11 insertions, 5 deletions

diff --git a/docs/sphinx/qapidoc.py b/docs/sphinx/qapidoc.py
index f9683444b1..efcd84656f 100644
--- a/docs/sphinx/qapidoc.py
+++ b/docs/sphinx/qapidoc.py
@@ -272,14 +272,20 @@ class QAPISchemaGenRSTVisitor(QAPISchemaVisitor):
             if section.tag and section.tag == 'TODO':
                 # Hide TODO: sections
                 continue
+
+            if not section.tag:
+                # Sphinx cannot handle sectionless titles;
+                # Instead, just append the results to the prior section.
+                container = nodes.container()
+                self._parse_text_into_node(section.text, container)
+                nodelist += container.children
+                continue
+
             snode = self._make_section(section.tag)
-            if section.tag and section.tag.startswith('Example'):
+            if section.tag.startswith('Example'):
                 snode += self._nodes_for_example(dedent(section.text))
             else:
-                self._parse_text_into_node(
-                    dedent(section.text) if section.tag else section.text,
-                    snode,
-                )
+                self._parse_text_into_node(dedent(section.text), snode)
             nodelist.append(snode)
         return nodelist