Request: Pre-Start command

[AlexanderLanin]

What would you like to see

Problem description

In our setup python is provided by bazel. So it's not available directly at startup. Only after the user has executed bazel run //docs:ide_support python is available in an .venv directory. By that time the extension has already started and loaded the python parts - which fails.

While that might be a little specific, in general the extension simply assumes python is pre-installed, which may not always be the case.

[Error - 6:43:31 PM] Esbonio Language Server client: couldn't create connection to server.
Launching server using command /home/lla2hi/score/score/.venv_docs/bin/python failed. Error: spawn /home/lla2hi/score/score/.venv_docs/bin/python ENOENT
[client] Launching server using command /home/lla2hi/score/score/.venv_docs/bin/python failed. Error: spawn /home/lla2hi/score/score/.venv_docs/bin/python ENOENT

Workaround

When we run our command which provides python, and then reload the VS Code window (0.x).

With 1.x it's also sufficient to restart the language server. But it will only actually run once an rst file is open and not directly.

Proposal

Add an pre-start-for-language-server (startupAction, initializeCommand, onStartupCommand, preStartCommand etc) parameter where we could configure our bazel run //docs:ide_support command. Run that (once) before running any python code.

[alcarney]

I was going to say I was reluctant to add something like this, but as I was thinking through what the workarounds could be I realised the extension is kind of halfway here already and probably just needs some refinement to make it work well.

Here are some potential approaches, let me know what you think.

• There is the esbonio.server.enabled option, which could be set to false by default in the repo. Perhaps the bazel run //docs:ide_support could flip it to true when the interpreter is ready to be used. (I tried this recently and the extension does need some fixes for it to work properly)

• There is also the esbonio.server.pythonPath option, it should probably be changed to a list of strings (similar to the esbonio.sphinx.pythonCommand option) so that it could be changed to an arbitrary command.

  Is it possible to add have a target like bazel run //docs:run_python that depends on bazel run //docs:ide_support and starts the correct Python? It would require some additional tweaks but this approach should also work for implementing Enable using custom esbonio python package #924.