Cache the entire site-packages directory

PiperOrigin-RevId: 368258535

.github/workflows/build_and_minimal_test.yml

@@ -22,16 +22,18 @@ jobs:
       # before making changes to this step.
       uses: actions/cache@v2
       with:
-        # This path is specific to Ubuntu
-        path: ~/.cache/pip
+        # Cache installed Python packages instead of the pip download cache.
+        path: ${{ env.pythonLocation }}/lib/python${{ matrix.python-version }}/site-packages
         # Look to see if there is a cache hit for the corresponding setup.py.
         key: ${{ runner.os }}-py${{ matrix.python-version }}-pip-${{ hashFiles('setup.py') }}
         # Try the cache with a different setup.py.
         restore-keys: ${{ runner.os }}-py${{ matrix.python-version }}-pip-
     - name: Install dependencies
+      # Use `install -e` for local fedjax to prevent actual fedjax files from
+      # being packaged into cache.
       run: |
         python -m pip install --upgrade pip setuptools wheel
-        pip install .
+        pip install -e .
     - name: Test
       run: |
         python fedjax/fedjax_test.py