[docutils:bugs] #472 Node.previous_sibling is broken

- **status**: open --> closed-fixed
- **Priority**: 8 --> 5
- **Comment**:

This is a duplicate of [patches:#195], fixed in  Docutils 0.20.
Thanks for reporting, anyway.



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**[bugs:#472] Node.previous_sibling is broken**

**Status:** closed-fixed
**Created:** Mon Jun 05, 2023 03:42 PM UTC by flying sheep
**Last Updated:** Mon Jun 05, 2023 03:53 PM UTC
**Owner:** nobody


It doesn’t work as advertised, as it never returns `None`.

~~~
def previous_sibling(self):
    """Return preceding sibling node or ``None``."""
    try:
        return self.parent[self.parent.index(self)-1]
    except (AttributeError, IndexError):
        return None
~~~

This means that when `self` is the first child, i.e. `self.parent.index(self) == 0`,  then `self.parent[-1]` is returned. The last child, not `None`. If `len(node.parent) == 1`, that means `node.previous_sibling() is node`.

This in turn means that the HTML writer for `citation` elements will emit broken HTML, see https://github.com/mcmtroffaes/sphinxcontrib-bibtex/issues/329

This is pretty severe since it leads to broken HTML markup and therefore completely broken page layout.


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