`pywrangler sync` uses the wrong site-packages path on Windows

[andrewchang90]

Summary

On Windows, pywrangler sync does not copy installed dependencies into python_modules/.
That makes local development fail when the Pyodide runtime starts:

ModuleNotFoundError: No module named 'workers'

The same project works on macOS and deploys successfully.

Environment

• OS: Windows
• Python: 3.13.14
• uv: 0.12.5
• pywrangler / workers-py: 1.16.2

Reproduction

With a Python Worker project that has dependencies:

uv sync
uv run pywrangler dev

pywrangler dev then fails because modules that should have been synced cannot be imported.
python_modules/ is empty, or does not contain the expected packages.

Cause

pywrangler/sync.py chooses the source site-packages directory from the host
operating system:

site_packages_path = (
    f"lib/python{pyv}/site-packages" if os.name != "nt" else "Lib/site-packages"
)

On Windows, this makes it look in:

Lib/site-packages

But this environment targets Pyodide (emscripten/wasm32), and uv installs the packages using the POSIX-style layout:

lib/python<version>/site-packages

The copy step therefore reads from an empty directory and produces an empty python_modules/ directory.

Expected behavior

pywrangler sync should include project dependencies in python_modules/ on Windows, and pywrangler dev should start successfully.

Workaround

Installing directly into the destination avoids the host-dependent site-packages lookup:

uv pip install --target python_modules/ ...

Using the Pyodide-style lib/python<version>/site-packages path also fixes the immediate problem.

The local patch works, but it is overwritten when workers-py is reinstalled.

[andrewchang90]

Upgrading to 1.16.5 or later resolves the problem, so the local workaround is no longer needed. Sorry for the noise.