Fast Pylance startup: don't block activation on environment enumeration#26019
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Make interpreter resolution non-blocking so Pylance can start immediately, even during a full environment refresh: - interpreterService.getActiveInterpreter races resolution against a 100ms timeout, serving the last-known/persisted interpreter when discovery is slow (the real value still resolves and updates listeners). - activationManager no longer awaits auto-select interpreter; it races a short timeout. - pythonEnvironments/index sets Conda.setSkipDeepProbe(true) when the environments extension is active, and conda.ts honors it to avoid slow deep probes. - envExt/api.legacy and interpreterService de-duplicate in-flight resolutions. - testController: defer project discovery (return undefined and self-heal on environment change) instead of throwing 'No Python environment found' when an env isn't assigned yet during fast startup. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
rchiodo
added
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Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
heejaechang
approved these changes
Jun 24, 2026
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Related issue
Part of #26020
Summary
Make Python interpreter resolution non-blocking so Pylance can start immediately, even while the environment extension is doing a full refresh on first run.
Previously, activation awaited interpreter auto-selection and
getActiveInterpreter()could block for the entire environment-enumeration window (tens of seconds on large/conda setups), which delayed the language server from starting.Changes
interpreter/interpreterService.ts–getActiveInterpreter()now races resolution against a ~100ms timeout. If discovery is slow it returns the last-known/persisted interpreter immediately; the real resolution still completes in the background and notifies listeners, so the value self-corrects after a refresh. In-flight resolutions are de-duplicated, and completion is reported viaonDidChangeso the eventual interpreter propagates to Pylance without a server restart.activation/activationManager.ts– No longer blocks activation on auto-select; it races a short timeout. Auto-selection still runs exactly once and completes in the background.pythonEnvironments/.../conda.ts+pythonEnvironments/index.ts– AddConda.setSkipDeepProbe(true)when the environments extension owns discovery, so startup no longer triggers slow sequential registry /conda info --jsonprobes (the env extension / PET already discovers conda).python.condaPathremains an escape hatch.envExt/api.legacy.ts– De-duplicate in-flight active-interpreter resolutions and keep reporting changes viareportActiveInterpreterChanged.testing/testController/...– Defer project discovery and self-heal on environment change instead of throwingNo Python environment foundwhen an env hasn't been assigned yet during fast startup.Tests
Updated/added unit tests for
activationManager,interpreterService,conda, the legacy env API, and the test controller.Notes
This is part of a cross-repo effort to speed up Pylance startup (companion PRs in
vscode-python-environmentsand the Pylance server).