Refactor Speedup

Rewrite the Pyodide test speedup code to clear the local directory.

Why? What?

We previously sped up the Pyodide tests by retaining a Pyodide instance across test runs. When combined with Vitest “watch” and HMR, tests become essentially instant. Even when running under debug mode.

But we now have a flaw. We still want isolation on the pyodide_components code, as part of testing. We don’t want the “local” filesystem, where things are imported from, to still have a directory with __init__.py etc. in it.

We also have a flaw with “self”. It isn’t part of the Pyodide state. It’s the worker, as part of Happy DOM. Since we assign to self, we need to clear those assignments from call to call.

Removing the directory in beforeEach

Let’s address that first in beforeEach, where we are currently restoring the startup, empty state of Pyodide.

In the first attempt, through JS and the pyodide.FS.rmdir and friends, we ran into all kinds of timing issues. It appears there is something async going on deep down in emscripten. A switch to Python fixed it. Here’s the new beforeEach:

beforeEach(async () => {
  // On each test, reset to an "empty" interpreter
  thisPyodide.pyodide_py._state.restore_state(initialPyodideState);
  self.pyodide = thisPyodide;

  // If the pyodide_components directory exists, let's delete it
  // and start over
  const pathInfo = self.pyodide.FS.analyzePath("pyodide_components");
  if (pathInfo.exists) {
    self.pyodide.runPython(
      "import shutil; shutil.rmtree('pyodide_components')"
    );
  }
  self.pyodide.runPython("import os; os.mkdir('pyodide_components')");
});

Resetting self

In beforeEach, we’ll also clear self.pyodide_components and self.registry:

  // The "self" needs resetting
  if (self.pyodide_components) delete self.pyodide_components;
  if (self.registry) delete self.registry;

Wrapup

With this in place, we’re now ready to return to building up the registry.