Disable language services if Pyrefly extension installed + active

[kinto0]

For #24850

Summary:
Background:
A new typechecker called Pyrefly will be featured at Pycon with a talk, website/sandbox (still WIP), and extension (still WIP). This extension will provide ultrafast typechecking and language services. When the Pyrefly extension is installed, ms-python.python should not start Jedi or Pylance unless python.pyrefly.disableLanguageServices is set to true.

Because of the separation of vscode's getExtensions API and config reading logic, I chose to augment DefaultLSType with fallback information in case Pyrefly is disabled. This lets configSettings pick the correct jedi/pylance without knowing if Pyrefly will be enabled or disabled.

Test Plan:
still can't get pyright to work in the local extension build but I do see my breakpoints hit and the correct languageServer set

lowerquality.mp4

[kinto0]

Thanks for the quick review @rchiodo! I did not realize you would see draft PRs yet... I just updated the summary so it should make more sense.

[rchiodo]

When you did this part:

Followed guide here. When running extension locally, I don't see any language services ever (before / after my changes). I'd appreciate help testing this integration since I'm not confident the configuration is set correctl

Did you clone into the extensions folder for vscode? I think that's what those directions are asking you to do? @karthiknadig would know more. Pylance would have to be installed in the extensions folder I think for your testing to work

[rchiodo]

This error:

2025-04-16 15:22:19.725 [error] [
  'Starting language server, Class name = p, completed in 11208ms, has a falsy return value, , Return Value: undefined',
  [Error: command 'pyright.createtypestub' already exists
  	at cw.registerCommand (file:///private/var/folders/x0/z3j4vbzs3wqd0ynb6q24jglm0000gn/T/AppTranslocation/58C97911-06B4-4CA7-9068-D7D7F655735D/d/Visual%20Studio%20Code%202.app/Contents/Resources/app/out/vs/workbench/api/node/extensionHostProcess.js:115:31527)
  	at Object.registerCommand (file:///private/var/folders/x0/z3j4vbzs3wqd0ynb6q24jglm0000gn/T/AppTranslocation/58C97911-06B4-4CA7-9068-D7D7F655735D/d/Visual%20Studio%20Code%202.app/Contents/Resources/app/out/vs/workbench/api/node/extensionHostProcess.js:157:36729)
  	at t.ExecuteCommandFeature.register (/Users/kylei/.vscode/extensions/ms-python.python-2025.4.0-darwin-arm64/out/client/extension.js:2:2101514)
  	at t.ExecuteCommandFeature.initialize (/Users/kylei/.vscode/extensions/ms-python.python-2025.4.0-darwin-arm64/out/client/extension.js:2:2101091)
  	at P.initializeFeatures (/Users/kylei/.vscode/extensions/ms-python.python-2025.4.0-darwin-arm64/out/client/extension.js:2:2041419)
  	at P.doInitialize (/Users/kylei/.vscode/extensions/ms-python.python-2025.4.0-darwin-arm64/out/client/extension.js:2:2027694)
  	at async P.start (/Users/kylei/.vscode/extensions/ms-python.python-2025.4.0-darwin-arm64/out/client/extension.js:2:2024707)
  	at async Object.start (/Users/kylei/.vscode/extensions/ms-python.vscode-pylance-2025.4.1/dist/extension.bundle.js:1:148233)
  	at async _0x317b05._startClient (/Users/kylei/.vscode/extensions/ms-python.vscode-pylance-2025.4.1/dist/extension.bundle.js:1:84298)
  	at async _0x317b05._createNewRequest (/Users/kylei/.vscode/extensions/ms-python.vscode-pylance-2025.4.1/dist/extension.bundle.js:1:83758)
  	at async _0x317b05._enqueueRequestAndWaitForRun (/Users/kylei/.vscode/extensions/ms-python.vscode-pylance-2025.4.1/dist/extension.bundle.js:1:83000)
  	at async _0x317b05.startClient (/Users/kylei/.vscode/extensions/ms-python.vscode-pylance-2025.4.1/dist/extension.bundle.js:1:82482)
  	at async h.start (/Users/kylei/.vscode/extensions/ms-python.python-2025.4.0-darwin-arm64/out/client/extension.js:2:39831)]
]

Usually happens when pyright and pylance are enabled at the same time. It might also happen if pylance is started twice for some reason.

[karthiknadig]

@kinto0 Please look into and accept the CLA. Otherwise we can't merge this.

[kinto0]

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[kinto0]

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[Crazy40528]

kinto0:kinto/disable-with-pyrefly