Some Sphinx inventories cannot be parsed

[lmichaelis]

Describe the bug

Some Sphinx inventories (see below) fail parsing with the following traceback:

Traceback

Traceback (most recent call last):
  File "C:\Users\lmichaelis\AppData\Local\Programs\Python\Python39\lib\runpy.py", line 197, in _run_module_as_main
    return _run_code(code, main_globals, None,
  File "C:\Users\lmichaelis\AppData\Local\Programs\Python\Python39\lib\runpy.py", line 87, in _run_code
    exec(code, run_globals)
  File "C:\Users\lmichaelis\xxx\.venv\Scripts\mkdocs.exe\__main__.py", line 7, in <module>
  File "c:\users\lmichaelis\xxx\.venv\lib\site-packages\click\core.py", line 1126, in __call__
    return self.main(*args, **kwargs)
  File "c:\users\lmichaelis\xxx\.venv\lib\site-packages\click\core.py", line 1051, in main
    rv = self.invoke(ctx)
  File "c:\users\lmichaelis\xxx\.venv\lib\site-packages\click\core.py", line 1657, in invoke
    return _process_result(sub_ctx.command.invoke(sub_ctx))
  File "c:\users\lmichaelis\xxx\.venv\lib\site-packages\click\core.py", line 1393, in invoke
    return ctx.invoke(self.callback, **ctx.params)
  File "c:\users\lmichaelis\xxx\.venv\lib\site-packages\click\core.py", line 752, in invoke
    return __callback(*args, **kwargs)
  File "c:\users\lmichaelis\xxx\.venv\lib\site-packages\mkdocs\__main__.py", line 250, in build_command
    build.build(cfg, dirty=not clean)
  File "c:\users\lmichaelis\xxx\.venv\lib\site-packages\mkdocs\commands\build.py", line 311, in build
    env = config.plugins.run_event('env', env, config=config, files=files)
  File "c:\users\lmichaelis\xxx\.venv\lib\site-packages\mkdocs\plugins.py", line 520, in run_event
    result = method(item, **kwargs)
  File "c:\users\lmichaelis\xxx\.venv\lib\site-packages\mkdocstrings\plugin.py", line 242, in on_env
    for page, identifier in collections.ChainMap(*(fut.result() for fut in self._inv_futures)).items():
    for page, identifier in collections.ChainMap(*(fut.result() for fut in self._inv_futures)).items():
  File "C:\Users\lmichaelis\AppData\Local\Programs\Python\Python39\lib\concurrent\futures\_base.py", line 439, in result
  File "C:\Users\lmichaelis\AppData\Local\Programs\Python\Python39\lib\concurrent\futures\_base.py", line 391, in __get_result
    raise self._exception
  File "C:\Users\lmichaelis\AppData\Local\Programs\Python\Python39\lib\concurrent\futures\thread.py", line 58, in run
    result = self.fn(*self.args, **self.kwargs)
  File "c:\users\lmichaelis\xxx\.venv\lib\site-packages\mkdocstrings\plugin.py", line 299, in _load_inventory
    result = dict(loader(content, url=url, **kwargs))
  File "c:\users\lmichaelis\xxx\.venv\lib\site-packages\mkdocstrings_handlers\python\handler.py", line 189, in load_inventory
    for item in Inventory.parse_sphinx(in_file, domain_filter=("py",)).values():  # noqa: WPS526
  File "c:\users\lmichaelis\xxx\.venv\lib\site-packages\mkdocstrings\inventory.py", line 129, in parse_sphinx
    items = [InventoryItem.parse_sphinx(line.decode("utf8")) for line in lines]
  File "c:\users\lmichaelis\xxx\.venv\lib\site-packages\mkdocstrings\inventory.py", line 129, in <listcomp>
    items = [InventoryItem.parse_sphinx(line.decode("utf8")) for line in lines]
  File "c:\users\lmichaelis\xxx\.venv\lib\site-packages\mkdocstrings\inventory.py", line 56, in parse_sphinx
    raise ValueError(line)
ValueError: index std:doc -1  Werkzeug

Even though I encountered this error using the new Python handler this error occurs in mkdocstrings as the traceback shows.

To Reproduce

Steps to reproduce the behavior:

1. Set up a basic mkdocstrings configuration
2. Add any of the following inventories as an import to the Python handler
   • https://werkzeug.palletsprojects.com/en/2.0.x/objects.inv
   • https://flask-login.readthedocs.io/en/latest/objects.inv
   • https://flask-sqlalchemy.palletsprojects.com/en/2.x/objects.inv
3. Run mkdocs build or mkdocs serve

My Configuration

  - mkdocstrings:
     default_handler: python
     handlers:
       python:
         paths: ['.']
         import:
           - 'https://werkzeug.palletsprojects.com/en/2.0.x/objects.inv'
         options:
           show_root_heading: false
           docstring_style: 'google'
           show_source: true
           show_root_toc_entry: false
           heading_level: 3

Expected behavior

The inventory is downloaded, parsed and used to link to external documentation.

Information (please complete the following information):

• OS: Microsoft Windows, Ubuntu Linux
• Browser: n/a
• mkdocstrings version: 0.19.0

Additional context

I have narrowed it down to the regex used in inventory.py:

mkdocstrings/src/mkdocstrings/inventory.py

Line 49 in efa00b2

sphinx_item_regex = re.compile(r"^(.+?)\s+(\S+):(\S+)\s+(-?\d+)\s+(\S+)\s+(.*)$")

It is used to validate one line of the inventory in parse_sphinx() where it fails to match the line:

mkdocstrings/src/mkdocstrings/inventory.py

Lines 51 to 62 in efa00b2

	@classmethod
	def parse_sphinx(cls, line: str) -> "InventoryItem":
	"""Parse a line from a Sphinx v2 inventory file and return an `InventoryItem` from it."""
	match = cls.sphinx_item_regex.search(line)
	if not match:
	raise ValueError(line)
	name, domain, role, priority, uri, dispname = match.groups()
	if uri.endswith("$"):
	uri = uri[:-1] + name
	if dispname == "-":
	dispname = name
	return cls(name, domain, role, uri, priority, dispname)

Altering one character of the regex seems to fix it though I am not sure of any other effects it might have:

Before: ^(.+?)\s+(\S+):(\S+)\s+(-?\d+)\s+(\S+)\s+(.*)$
After:  ^(.+?)\s+(\S+):(\S+)\s+(-?\d+)\s+(\S+)\s*(.*)$