Pytest-html plugin throws misleading error if log filepath has unsupported special characters for underlying OS

Hi,

This is related to pytest throwing misleading exception when log filepath contains special characters that are not supported by Windows OS in filenames.

Below is the exception that I got-
Traceback (most recent call last): File "C:\Users\admin\mtarun\vmware\code\mangle-yaan-service\test_runner.py", line 693, in <module> main() File "C:\Users\admin\mtarun\vmware\code\mangle-yaan-service\test_runner.py", line 646, in main pytest_status = run_pytest(pytest_cmdline, run_id=args.run_id) File "C:\Users\admin\mtarun\vmware\code\mangle-yaan-service\test_runner.py", line 330, in run_pytest status = pytest.main(*args, **kwargs) File "C:\Users\admin\AppData\Local\Packages\PythonSoftwareFoundation.Python.3.9_qbz5n2kfra8p0\LocalCache\local-packages\Python3 9\site-packages\_pytest\config\__init__.py", line 124, in main ret = config.hook.pytest_cmdline_main( File "C:\Users\admin\AppData\Local\Packages\PythonSoftwareFoundation.Python.3.9_qbz5n2kfra8p0\LocalCache\local-packages\Python3 9\site-packages\pluggy\hooks.py", line 286, in __call__ return self._hookexec(self, self.get_hookimpls(), kwargs) File "C:\Users\admin\AppData\Local\Packages\PythonSoftwareFoundation.Python.3.9_qbz5n2kfra8p0\LocalCache\local-packages\Python3 9\site-packages\pluggy\manager.py", line 93, in _hookexec return self._inner_hookexec(hook, methods, kwargs) File "C:\Users\admin\AppData\Local\Packages\PythonSoftwareFoundation.Python.3.9_qbz5n2kfra8p0\LocalCache\local-packages\Python3 9\site-packages\pluggy\manager.py", line 84, in <lambda> self._inner_hookexec = lambda hook, methods, kwargs: hook.multicall( File "C:\Users\admin\AppData\Local\Packages\PythonSoftwareFoundation.Python.3.9_qbz5n2kfra8p0\LocalCache\local-packages\Python3 9\site-packages\pluggy\callers.py", line 208, in _multicall return outcome.get_result() File "C:\Users\admin\AppData\Local\Packages\PythonSoftwareFoundation.Python.3.9_qbz5n2kfra8p0\LocalCache\local-packages\Python3 9\site-packages\pluggy\callers.py", line 80, in get_result raise ex[1].with_traceback(ex[2]) File "C:\Users\admin\AppData\Local\Packages\PythonSoftwareFoundation.Python.3.9_qbz5n2kfra8p0\LocalCache\local-packages\Python3 9\site-packages\pluggy\callers.py", line 187, in _multicall res = hook_impl.function(*args) File "C:\Users\admin\AppData\Local\Packages\PythonSoftwareFoundation.Python.3.9_qbz5n2kfra8p0\LocalCache\local-packages\Python3 9\site-packages\_pytest\main.py", line 240, in pytest_cmdline_main return wrap_session(config, _main) File "C:\Users\admin\AppData\Local\Packages\PythonSoftwareFoundation.Python.3.9_qbz5n2kfra8p0\LocalCache\local-packages\Python3 9\site-packages\_pytest\main.py", line 228, in wrap_session config.hook.pytest_sessionfinish( File "C:\Users\admin\AppData\Local\Packages\PythonSoftwareFoundation.Python.3.9_qbz5n2kfra8p0\LocalCache\local-packages\Python3 9\site-packages\pluggy\hooks.py", line 286, in __call__ return self._hookexec(self, self.get_hookimpls(), kwargs) File "C:\Users\admin\AppData\Local\Packages\PythonSoftwareFoundation.Python.3.9_qbz5n2kfra8p0\LocalCache\local-packages\Python3 9\site-packages\pluggy\manager.py", line 93, in _hookexec return self._inner_hookexec(hook, methods, kwargs) File "C:\Users\admin\AppData\Local\Packages\PythonSoftwareFoundation.Python.3.9_qbz5n2kfra8p0\LocalCache\local-packages\Python3 9\site-packages\pluggy\manager.py", line 84, in <lambda> self._inner_hookexec = lambda hook, methods, kwargs: hook.multicall( File "C:\Users\admin\AppData\Local\Packages\PythonSoftwareFoundation.Python.3.9_qbz5n2kfra8p0\LocalCache\local-packages\Python3 9\site-packages\pluggy\callers.py", line 203, in _multicall gen.send(outcome) File "C:\Users\admin\AppData\Local\Packages\PythonSoftwareFoundation.Python.3.9_qbz5n2kfra8p0\LocalCache\local-packages\Python3 9\site-packages\_pytest\terminal.py", line 716, in pytest_sessionfinish outcome.get_result() File "C:\Users\admin\AppData\Local\Packages\PythonSoftwareFoundation.Python.3.9_qbz5n2kfra8p0\LocalCache\local-packages\Python3 9\site-packages\pluggy\callers.py", line 80, in get_result raise ex[1].with_traceback(ex[2]) File "C:\Users\admin\AppData\Local\Packages\PythonSoftwareFoundation.Python.3.9_qbz5n2kfra8p0\LocalCache\local-packages\Python3 9\site-packages\pluggy\callers.py", line 187, in _multicall res = hook_impl.function(*args) File "C:\Users\admin\AppData\Local\Packages\PythonSoftwareFoundation.Python.3.9_qbz5n2kfra8p0\LocalCache\local-packages\Python3 9\site-packages\pytest_html\plugin.py", line 614, in pytest_sessionfinish self._save_report(report_content) File "C:\Users\admin\AppData\Local\Packages\PythonSoftwareFoundation.Python.3.9_qbz5n2kfra8p0\LocalCache\local-packages\Python3 9\site-packages\pytest_html\plugin.py", line 588, in _save_report with open(self.logfile, "w", encoding="utf-8") as f: OSError: [Errno 22] Invalid argument: 'C:\\Users\\admin\\mtarun\\vmware\\code\\mangle-yaan-service\\logs\\mangle-yaan-test-report -13Aug2021_14:39:57.296895.html'

Ideally, pytest-html should check if there are any unsupported characters in log filepath and throw more informative exception for the same. Can we get a list of special characters that are not supported by specific OS in filenames using any python library? If yes, then we can add a check for log filepath if it has any such special characters that are not supported by underlying OS

Start in pytest_html/plugin.py at pytest_sessionfinish and _save_report, where the report is opened at the configured logfile path. Reproduce the Windows invalid-filename case shown in the traceback, then verify that unsupported path characters produce a more informative error and that normal paths still save the report.