markdown: _uniform_outdent fails for empty text

[martingabelmann]

Problem Description

Short: pdoc fails for empty markdown codeblocks.

We use jupyter-nbconvert to convert Jupyter notebooks into markdown and embed them as examples into the pdoc documentation. This is why empty codeblocks may appear in our markdown, since empty Jupyter input cells are converted into empty code blocks... With pdoc-13.0.1 this worked flawlessly but seemed to got broken by any of the changes towards pdoc-13.1.0 (I suspect in the course of #525).

Steps to reproduce the behavior:

1. add empty code block to markdown docs
2. run pdoc

Traceback (most recent call last):
  File "/home/martin/.local/lib/python3.10/site-packages/pdoc/render_helpers.py", line 177, in to_html
    return pdoc.markdown2.markdown(  # type: ignore
  File "/home/martin/.local/lib/python3.10/site-packages/pdoc/markdown2/__init__.py", line 175, in markdown
    use_file_vars=use_file_vars, cli=cli).convert(text)
  File "/home/martin/.local/lib/python3.10/site-packages/pdoc/markdown2/__init__.py", line 360, in convert
    text = self._do_fenced_code_blocks(text)
  File "/home/martin/.local/lib/python3.10/site-packages/pdoc/markdown2/__init__.py", line 2098, in _do_fenced_code_blocks
    return self._fenced_code_block_re.sub(self._fenced_code_block_sub, text)
  File "/home/martin/.local/lib/python3.10/site-packages/pdoc/markdown2/__init__.py", line 2094, in _fenced_code_block_sub
    return self._code_block_sub(match, is_fenced_code_block=True)
  File "/home/martin/.local/lib/python3.10/site-packages/pdoc/markdown2/__init__.py", line 1994, in _code_block_sub
    return self._code_block_with_lexer_sub(codeblock, leading_indent, lexer, is_fenced_code_block)
  File "/home/martin/.local/lib/python3.10/site-packages/pdoc/markdown2/__init__.py", line 2043, in _code_block_with_lexer_sub
    _, codeblock = self._uniform_outdent(codeblock, max_outdent=leading_indent)
  File "/home/martin/.local/lib/python3.10/site-packages/pdoc/markdown2/__init__.py", line 2621, in _uniform_outdent
    outdent = min(i for i in whitespace if i is not None)
ValueError: min() arg is an empty sequence

System Information

pdoc: 13.1.0
Python: 3.10.10
Platform: Linux-6.2.9-arch1-1-x86_64-with-glibc2.37

Fix

I was able to fix it by adding a

        if not text:
            return text, text

at the top of the definition of _uniform_outdent in pdoc/markdown2/__init__.py. The result looks good to me, though I'm not familiar with the pdoc codebase and don't know whether this might break other stuff....

[mhils]

Thanks! This seems to be a regression in markdown2, I'll file a bug upstream. :)