SF.net SVN: docutils:[10197 ] trunk/docutils/docutils/ parsers/rst/states.py

Revision: 10197
          http://sourceforge.net/p/docutils/code/10197
Author:   milde
Date:     2025-08-08 18:23:50 +0000 (Fri, 08 Aug 2025)
Log Message:
-----------
Catch invalid node.parent when switching section levels.

Better error report for problems with the new section parsing algorithm.
See [bugs:#] and [bugs:#].

Modified Paths:
--------------
    trunk/docutils/docutils/parsers/rst/states.py

Modified: trunk/docutils/docutils/parsers/rst/states.py
===================================================================
--- trunk/docutils/docutils/parsers/rst/states.py	2025-08-07 06:35:37 UTC (rev 10196)
+++ trunk/docutils/docutils/parsers/rst/states.py	2025-08-08 18:23:50 UTC (rev 10197)
@@ -331,30 +331,42 @@
         title_styles = self.memo.title_styles
         parent_sections = self.parent.section_hierarchy()
         # current section level: (0 document, 1 section, 2 subsection, ...)
-        mylevel = len(parent_sections)
-        # Determine the level of the new section:
+        oldlevel = len(parent_sections)
+        # new section level:
         try:  # check for existing title style
-            level = title_styles.index(style) + 1
+            newlevel = title_styles.index(style) + 1
         except ValueError:  # new title style
             title_styles.append(style)
-            level = len(title_styles)
+            newlevel = len(title_styles)
         # The new level must not be deeper than an immediate child
         # of the current level:
-        if level > mylevel + 1:
-            styles = " ".join("/".join(s for s in style)
-                              for style in title_styles)
+        if newlevel > oldlevel + 1:
+            styles = ' '.join('/'.join(style) for style in title_styles)
             self.parent += self.reporter.severe(
                 'Inconsistent title style:'
-                f' skip from level {mylevel} to {level}.',
+                f' skip from level {oldlevel} to {newlevel}.',
                 nodes.literal_block('', source),
                 nodes.paragraph('', f'Established title styles: {styles}'),
                 line=lineno)
             return False
         # Update parent state:
-        self.memo.section_level = level
-        if level <= mylevel:
+        self.memo.section_level = newlevel
+        if newlevel <= oldlevel:
             # new section is sibling or higher up in the section hierarchy
-            self.parent = parent_sections[level-1].parent
+            new_parent = parent_sections[newlevel-1].parent
+            if new_parent is None:
+                styles = ' '.join('/'.join(style) for style in title_styles)
+                self.parent += self.reporter.severe(
+                    f'Cannot skip from level {oldlevel} to {newlevel}.'
+                    ' Current element has only {len(self.parent_sections)'
+                    ' parent sections.'
+                    ' (Mismatch of `memo.section_styles`,'
+                    ' and the root node of a nested parser?)',
+                    nodes.literal_block('', source),
+                    nodes.paragraph('', f'Established title styles: {styles}'),
+                    line=lineno)
+                return False
+            self.parent = new_parent
         return True
 
     def title_inconsistent(self, sourcetext, lineno):

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