Pyodide/wasm support: pure-Python wheel, worker transport, GlowScript host factory

.github/workflows/pure-wheel.yml

@@ -0,0 +1,58 @@
+name: Pure-Python wheel (wasm/Pyodide)
+
+# Builds the VPYTHON_PURE_PYTHON=1 wheel (py3-none-any) that Pyodide/micropip
+# and other wasm targets can install — they cannot use platform wheels.
+# Consumers (e.g. trinket) pin the artifact by URL + sha256; a GitHub release
+# gets the wheel attached automatically so pins survive artifact expiry.
+
+on:
+  workflow_dispatch:
+  push:
+    branches: [master, pyodide-packaging]
+  release:
+    types: [published]
+
+jobs:
+  pure-wheel:
+    runs-on: ubuntu-latest
+    permissions:
+      contents: write  # needed only for the release-asset upload step
+    steps:
+      - uses: actions/checkout@v7
+        with:
+          fetch-depth: 0  # setuptools_scm-style dev versions need history
+
+      - uses: actions/setup-python@v6
+        with:
+          python-version: "3.12"
+
+      - name: Build pure wheel
+        run: |
+          pip install build
+          VPYTHON_PURE_PYTHON=1 python -m build --wheel --outdir dist
+          ls -l dist
+
+      - name: Verify wheel is py3-none-any and imports
+        run: |
+          python - <<'EOF'
+          import glob, sys
+          w = glob.glob('dist/*.whl')
+          assert w and w[0].endswith('py3-none-any.whl'), f"not a pure wheel: {w}"
+          print("pure wheel:", w[0])
+          EOF
+          pip install dist/*.whl
+          python -c "import vpython; print('import ok', vpython.__version__)"
+
+      - name: Checksum
+        run: shasum -a 256 dist/*.whl | tee dist/SHA256SUMS
+
+      - uses: actions/upload-artifact@v4
+        with:
+          name: vpython-pure-wheel
+          path: dist/
+
+      - name: Attach wheel to release
+        if: github.event_name == 'release'
+        env:
+          GH_TOKEN: ${{ github.token }}
+        run: gh release upload "${{ github.event.release.tag_name }}" dist/*.whl dist/SHA256SUMS --clobber

.github/workflows/upload_pypi.yml

@@ -4,8 +4,14 @@ on:
   release:
     types: [created]
 
+# Pre-releases exist to host pinned artifacts (see pure-wheel.yml) — they must
+# NEVER publish to PyPI. Guarded per-job because uploads happen per-job: on
+# 2026-08-15 a pre-release tag partially published 7.6.6.dev0 (sdist + mac/win
+# wheels) before the linux legs failed.
+
 jobs:
   wheels:
+    if: ${{ !github.event.release.prerelease }}
 
     strategy:
       max-parallel: 4
@@ -40,6 +46,7 @@ jobs:
         twine upload dist/*.whl
 
   linux_wheels:
+    if: ${{ !github.event.release.prerelease }}
     runs-on: ubuntu-latest
     steps:
     - uses: actions/checkout@v7
@@ -71,6 +78,7 @@ jobs:
         twine upload dist/vpython-*-manylinux*.whl
 
   linux_aarch64_wheels:
+    if: ${{ !github.event.release.prerelease }}
     runs-on: ubuntu-latest
     steps:
     - uses: actions/checkout@v7
@@ -100,6 +108,7 @@ jobs:
         twine upload dist/vpython-*-manylinux*.whl
 
   sdist:
+    if: ${{ !github.event.release.prerelease }}
     runs-on: ubuntu-latest
     steps:
     - uses: actions/checkout@v7

.gitignore

@@ -64,3 +64,7 @@ docs/_build/
 
 # PyBuilder
 target/
+
+# local virtualenvs
+.venv/
+venv/

setup.py

@@ -1,13 +1,28 @@
+import os
+
 from setuptools import setup
 
 from distutils.extension import Extension
 
-try:
-    from Cython.Build import cythonize
-    USE_CYTHON = True
-    extensions = cythonize('vpython/cyvector.pyx')
-except ImportError:
-    extensions = [Extension('vpython.cyvector', ['vpython/cyvector.c'])]
+# Set VPYTHON_PURE_PYTHON=1 to build with no C extension at all. The result is a
+# `py3-none-any` wheel, which is what Pyodide/micropip and other wasm targets
+# require — they cannot install a platform wheel, and declaring `ext_modules` is
+# what makes every wheel a platform wheel.
+#
+# Nothing is lost but speed: `_vector_import_helper` already falls back to the
+# pure-Python `vector` implementation when `cyvector` cannot be imported, so the
+# same source runs either way. Ordinary builds are unchanged — this is opt-in.
+PURE_PYTHON = os.environ.get('VPYTHON_PURE_PYTHON', '').strip() not in ('', '0', 'false', 'False')
+
+if PURE_PYTHON:
+    extensions = []
+else:
+    try:
+        from Cython.Build import cythonize
+        USE_CYTHON = True
+        extensions = cythonize('vpython/cyvector.pyx')
+    except ImportError:
+        extensions = [Extension('vpython.cyvector', ['vpython/cyvector.c'])]
 
 
 install_requires = ['jupyter', 'jupyter-server-proxy', 'jupyterlab-vpython>=3.1.8', 'notebook>=7.0.0', 'numpy', 'ipykernel',
@@ -35,14 +50,19 @@
           'Topic :: Multimedia :: Graphics :: 3D Rendering',
           'Topic :: Scientific/Engineering :: Visualization',
     ],
-    ext_modules=extensions,
     install_requires=install_requires,
-    python_requires=">=3.8",
+    python_requires=">=3.8",   # importlib.metadata, used in vpython/__init__.py
     package_data={'vpython': ['vpython_data/*',
                               'vpython_libraries/*',
                               'vpython_libraries/images/*']},
 )
 
+# `ext_modules` is added only for a normal build. Omitting the key entirely (as
+# opposed to passing an empty list) is what makes setuptools tag the wheel
+# `py3-none-any` rather than a platform wheel.
+if not PURE_PYTHON:
+    setup_args['ext_modules'] = extensions
+
 try:
     setup(**setup_args)
 except SystemExit as e:

tests/conftest.py

@@ -0,0 +1,10 @@
+"""Make the in-tree ``vpython`` package importable regardless of cwd.
+
+The repo root is prepended (not appended) so these tests always exercise the
+working tree rather than any copy of vpython installed in site-packages.
+"""
+
+import os
+import sys
+
+sys.path.insert(0, os.path.dirname(os.path.dirname(os.path.abspath(__file__))))