build(tests): Update to latest and greatest caching

Author: tony

.github/workflows/tests.yml

@@ -19,16 +19,56 @@ jobs:
       uses: actions/setup-python@v1
       with:
         python-version: ${{ matrix.python-version }}
-    - name: Install dependencies
+
+    - name: Get full Python version
+      id: full-python-version
+      shell: bash
+      run: echo ::set-output name=version::$(python -c "import sys; print('-'.join(str(v) for v in sys.version_info))")
+
+    - name: Install poetry
       run: |
-        python -m pip install --upgrade poetry
-        poetry install
-    - name: Lint with flake8
+        curl -O -sSL https://raw.githubusercontent.com/sdispater/poetry/master/get-poetry.py
+        python get-poetry.py -y
+        echo "::set-env name=PATH::$HOME/.poetry/bin:$PATH"
+        rm get-poetry.py
+
+    - name: Get poetry cache paths from config
       run: |
-        poetry run flake8
+        echo ::set-env name=poetry_cache_dir::$(poetry config --list | sed -n 's/.*cache-dir = //p' | sed -e 's/^"//' -e 's/"$//')
+        echo ::set-env name=poetry_virtualenvs_path::$(poetry config --list | sed -n 's/.*virtualenvs.path = .* # //p' | sed -e 's/^"//' -e 's/"$//')
+
+    - name: Configure poetry
+      shell: bash
+      run: poetry config virtualenvs.in-project true
+
+    - name: Set up cache
+      uses: actions/cache@v2
+      id: cache
+      with:
+        path: |
+          .venv
+          {{ env.poetry_cache_dir }}
+          {{ env.poetry_virtualenvs_path }}
+        key: venv-${{ runner.os }}-${{ steps.full-python-version.outputs.version }}-${{ hashFiles('**/poetry.lock') }}
+
+    - name: Ensure cache is healthy
+      if: steps.cache.outputs.cache-hit == 'true'
+      shell: bash
+      run: poetry run pip --version >/dev/null 2>&1 || rm -rf .venv
+
+    - name: Upgrade pip
+      shell: bash
+      run: poetry run python -m pip install pip -U
+
+    - name: Install dependencies
+      run: poetry install -E "docs test coverage lint format"
+
+    - name: Lint with flake8
+      run: poetry run flake8
+
     - name: Test with pytest
-      run: |
-        poetry run py.test --cov=./ --cov-report=xml
+      run: poetry run py.test --cov=./ --cov-report=xml
+
     - uses: codecov/codecov-action@v1
       with:
         token: ${{ secrets.CODECOV_TOKEN }}