Fail loudly instead of hanging forever when no frontend connects (#281) - #292
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…#281) The notebook path busy-waited unboundedly on the websocket handshake at import time. Frontends that never run vpython's injected JavaScript — VS Code notebooks, Google Colab — therefore hung the kernel silently inside 'import vpython'. Now a bounded wait (default 30s, VPYTHON_CONNECT_TIMEOUT to override) raises a RuntimeError that names the detected environment (VS Code / Colab / generic), points at working environments, and links the tracking issue. Pure-python helper, fully unit tested.
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Addresses the worst half of #281: in any notebook frontend that never runs vpython's injected JavaScript — VS Code notebooks and Google Colab being the common cases —
import vpythonbusy-waited forever on the websocket handshake, silently hanging the kernel.This does not make VPython work in those environments (that's the renderer/adapter work, tracked separately) — it converts an indefinite silent hang into a prompt, actionable error.
What changes
while (not wsConnected): sleep(0.1)at import time inwith_notebook.pybecomes a bounded wait — default 30 s, overridable viaVPYTHON_CONNECT_TIMEOUTfor genuinely slow first-runs (nbextension transfer on cold environments).RuntimeErrorwith a message that:VSCODE_PID/VSCODE_CWD, Colab viaCOLAB_RELEASE_TAG/COLAB_GPU, or a generic explanation),vpython/_frontend_wait.py) with injected clock/sleep/environ, so it's fully unit-tested (6 new tests; suite now 14) without any kernel or websocket machinery.Not changed
Normal Jupyter/Lab flows are unaffected — the wait still returns the moment the frontend connects, typically within a couple of seconds.
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https://claude.ai/code/session_01G7y9rTA1r8r8EhEnPSQenR