build: Add Scala 3 to CI matrix

Author: felixbr

.github/workflows/continuous-integration.yml

@@ -21,7 +21,8 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        scala: [2.12.12, 2.13.6]
+        # If you update the Scala 3 version, make sure to update the conditionals further down!
+        scala: [2.12.12, 2.13.6, 3.0.2]
         java: ['1.8', '1.11']
     runs-on: ubuntu-latest
     steps:
@@ -51,9 +52,20 @@ jobs:
           if [ -f ~/.sbt ]; then
             find ~/.sbt         -name "*.lock"               -delete
           fi
+
+        # coverage doesn't really work with Scala 3 yet so we only run it on Scala 2, which should be sufficient anyway
       - name: test
         run: ${{ format('./sbt ++{0} clean coverage test coverageReport', matrix.scala) }}
+        if: matrix.scala != '3.0.2'
+      - name: test
+        run: ${{ format('./sbt "++{0} -v clean; ++{0} test"', matrix.scala) }}
+        if: matrix.scala == '3.0.2'
+
+        # coverage doesn't really work with Scala 3 yet so we only run it on Scala 2, which should be sufficient anyway
       - name: coverage
         run: ${{ format('./sbt ++{0} coverageAggregate', matrix.scala) }}
+        if: matrix.scala != '3.0.2'
+        # coverage doesn't really work with Scala 3 yet so we only run it on Scala 2, which should be sufficient anyway
       - name: upload coverage
         uses: codecov/codecov-action@v2
+        if: matrix.scala != '3.0.2'