[BUG] NameError: name 'ThreadedRunner' is not defined

[vigenere23]

Relates to #2036 (https://github.com/plotly/dash/pull/2036/files#diff-103dd9b465768e0bec146c9ea9b04b9e762d9a6e2532c18e3ec4887a987e8d13)

Describe your context

Import error on the new 2.4.0 update when testing my app with pytest?

dash                                            2.4.0     
dash-core-components                            2.0.0     
dash-html-components                            2.0.0     
dash-table                                      5.0.0 

Describe the bug

Traceback (most recent call last):
  File ".venv/bin/pytest", line 8, in <module>
    sys.exit(console_main())
  File ".venv/lib/python3.9/site-packages/_pytest/config/__init__.py", line 185, in console_main
    code = main()
  File ".venv/lib/python3.9/site-packages/_pytest/config/__init__.py", line 143, in main
    config = _prepareconfig(args, plugins)
  File ".venv/lib/python3.9/site-packages/_pytest/config/__init__.py", line 318, in _prepareconfig
    config = pluginmanager.hook.pytest_cmdline_parse(
  File ".venv/lib/python3.9/site-packages/pluggy/_hooks.py", line 265, in __call__
    return self._hookexec(self.name, self.get_hookimpls(), kwargs, firstresult)
  File ".venv/lib/python3.9/site-packages/pluggy/_manager.py", line 80, in _hookexec
    return self._inner_hookexec(hook_name, methods, kwargs, firstresult)
  File ".venv/lib/python3.9/site-packages/pluggy/_callers.py", line 55, in _multicall
    gen.send(outcome)
  File ".venv/lib/python3.9/site-packages/_pytest/helpconfig.py", line 100, in pytest_cmdline_parse
    config: Config = outcome.get_result()
  File ".venv/lib/python3.9/site-packages/pluggy/_result.py", line 60, in get_result
    raise ex[1].with_traceback(ex[2])
  File ".venv/lib/python3.9/site-packages/pluggy/_callers.py", line 39, in _multicall
    res = hook_impl.function(*args)
  File ".venv/lib/python3.9/site-packages/_pytest/config/__init__.py", line 1003, in pytest_cmdline_parse
    self.parse(args)
  File ".venv/lib/python3.9/site-packages/_pytest/config/__init__.py", line 1283, in parse
    self._preparse(args, addopts=addopts)
  File ".venv/lib/python3.9/site-packages/_pytest/config/__init__.py", line 1172, in _preparse
    self.pluginmanager.load_setuptools_entrypoints("pytest11")
  File ".venv/lib/python3.9/site-packages/pluggy/_manager.py", line 287, in load_setuptools_entrypoints
    plugin = ep.load()
  File "/usr/local/lib/python3.9/importlib/metadata.py", line 86, in load
    module = import_module(match.group('module'))
  File "/usr/local/lib/python3.9/importlib/__init__.py", line 127, in import_module
    return _bootstrap._gcd_import(name[level:], package, level)
  File "<frozen importlib._bootstrap>", line 1030, in _gcd_import
  File "<frozen importlib._bootstrap>", line 1007, in _find_and_load
  File "<frozen importlib._bootstrap>", line 986, in _find_and_load_unlocked
  File "<frozen importlib._bootstrap>", line 680, in _load_unlocked
  File ".venv/lib/python3.9/site-packages/_pytest/assertion/rewrite.py", line 170, in exec_module
    exec(co, module.__dict__)
  File ".venv/lib/python3.9/site-packages/dash/testing/plugin.py", line 98, in <module>
    def dash_thread_server() -> ThreadedRunner:
NameError: name 'ThreadedRunner' is not defined

Expected behavior

No import error.

[alexcjohnson]

Thanks @vigenere23 - while we work on a fix for this, if you install dash[testing] instead of just dash this problem should disappear.

[alexcjohnson]

Fix released in Dash 2.4.1 - thanks again for reporting this @vigenere23!

[vigenere23]

Fix released in Dash 2.4.1 - thanks again for reporting this @vigenere23!

Saw that, updated and confirms it works. Thanks for the fix! :)