Add a workflow to test the packaging

Author: jtpio

.github/workflows/packaging.yml

@@ -0,0 +1,108 @@
+name: Packaging
+
+on:
+  push:
+    branches: [ master ]
+  pull_request:
+    branches: '*'
+
+env:
+  PIP_DISABLE_PIP_VERSION_CHECK: 1
+
+defaults:
+  run:
+    shell: bash -l {0}
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+    steps:
+    - name: Checkout
+      uses: actions/checkout@v2
+    - name: Install node
+      uses: actions/setup-node@v1
+      with:
+       node-version: '14.x'
+    - name: Install Python
+      uses: actions/setup-python@v2
+      with:
+        python-version: '3.9'
+        architecture: 'x64'
+    - name: Install dependencies
+      run: |
+        python -m pip install --upgrade pip wheel
+        python -m pip install setuptools jupyter_packaging "jupyterlab>=3,<4"
+    - name: Build PyPI distributions for ipywidgets
+      run: |
+        python setup.py sdist bdist_wheel
+    - name: Build PyPI distributions for jupyterlab_widgets
+      run: |
+        jlpm
+        jlpm run build
+        cd jupyterlab_widgets
+        python setup.py sdist bdist_wheel
+        cp ./dist/* ../dist
+    - name: Build checksum file
+      run: |
+        cd dist
+        sha256sum * | tee SHA256SUMS
+    - name: Upload distributions
+      uses: actions/upload-artifact@v2
+      with:
+        name: dist ${{ github.run_number }}
+        path: ./dist
+
+  install:
+    runs-on: ${{ matrix.os }}-latest
+    needs: [build]
+    strategy:
+      fail-fast: false
+      matrix:
+        os: [ubuntu, macos, windows]
+        python: ['3.6', '3.9']
+        include:
+          - python: '3.6'
+            dist: 'ipywidgets*.tar.gz'
+          - python: '3.9'
+            dist: 'ipywidgets*.whl'
+          - python: '3.9'
+            dist: 'jupyterlab_widgets*.tar.gz'
+          - os: windows
+            py_cmd: python
+          - os: macos
+            py_cmd: python3
+          - os: ubuntu
+            py_cmd: python
+    steps:
+      - name: Install Python
+        uses: actions/setup-python@v2
+        with:
+          python-version: ${{ matrix.python }}
+          architecture: 'x64'
+      - uses: actions/download-artifact@v2
+        with:
+          name: dist ${{ github.run_number }}
+          path: ./dist
+      - name: Install the prerequisites
+        run: |
+          ${{ matrix.py_cmd }} -m pip install pip wheel
+      - name: Install the package
+        run: |
+          cd dist
+          ${{ matrix.py_cmd }} -m pip install -vv ${{ matrix.dist }}
+      - name: Validate environment
+        run: |
+          ${{ matrix.py_cmd }} -m pip freeze
+          ${{ matrix.py_cmd }} -m pip check
+      - name: Validate the install
+        run: |
+          ${{ matrix.py_cmd }} -m pip install jupyterlab~=3.0
+
+          jupyter labextension list
+          jupyter labextension list 2>&1 | grep -ie "@jupyter-widgets/jupyterlab-manager.*enabled.*ok" -
+
+      - name: Check the Classic Notebook extension is installed
+        if: matrix.dist != 'jupyterlab_widgets*.tar.gz'
+        run: |
+          jupyter nbextension list
+          jupyter nbextension list 2>&1 | grep -ie "jupyter-js-widgets/extension.*enabled" -