Situation

When using a vscode.FileSystemProvider based file system and opening a python file, the extension stalls permanently and an error message is displayed on the console. Other file types provided by the same file system provider are working fine.

Reproduce

• Install VSCode file system provider example from here: https://github.com/microsoft/vscode-extension-samples/tree/main/fsprovider-sample
• Enable it as described in the sample code documentation.
• Open and edit a python file originating from that provider.

The console will display the following message:

Lintings failed on open
File: memfs:/file.py
Message: TypeError: Cannot read property 'uri' of undefined

A stacktrace is not provided. The extension host output will show this message in the 'Log (Window)' output:

 [warning] UNRESPONSIVE extension host, 'ms-python.python' took 100% of 5246.583ms, saved PROFILE here: 'file:///c%3A/Users/User/AppData/Local/Temp/1/exthost-6c0e65.cpuprofile' [{"id":"ms-python.python","total":5246261,"percentage":100}]

The extension is then stalled, the extension host does not react properly anymore and has to be terminated. The same effect happens with another file system provider implementation which has been heavily debugged and all other file types except python files are working fine.

Versions

• VSCode 1.56.2
• ms-python.python V2021.5.926500501