test(github): Enable PHP 8.0 testing (drupal-graphql#1166)

Author: klausi

.github/workflows/testing.yml

@@ -15,10 +15,16 @@ jobs:
       matrix:
         php-versions: ['7.3', '7.4']
         drupal-core: ['9.1.x']
-        # Extra run to also test on latest Drupal 8 and PHP 7.2.
+        phpstan: ['1']
         include:
+          # Extra run to also test on latest Drupal 8 and PHP 7.2.
           - php-versions: '7.2'
             drupal-core: '8.9.x'
+            phpstan: '1'
+          # PHPStan does not work on PHP 8 yet for us.
+          - php-versions: '8.0'
+            drupal-core: '9.1.x'
+            phpstan: '0'
     steps:
       - name: Checkout Drupal core
         uses: actions/checkout@v2
@@ -80,8 +86,8 @@ jobs:
           webonyx/graphql-php:^14.3 \
           drupal/typed_data:^1.0 \
           drupal/redirect:^1.6 \
-          phpstan/phpstan:0.12.69 \
-          mglaman/phpstan-drupal:^0.12.3 \
+          phpstan/phpstan:^0.12.70 \
+          mglaman/phpstan-drupal:^0.12.8 \
           phpstan/phpstan-deprecation-rules:^0.12.2 \
           jangregor/phpstan-prophecy:^0.8 \
           phpstan/phpstan-phpunit:^0.12
@@ -103,7 +109,7 @@ jobs:
 
       - name: Run PHPStan
         run: |
-          cd modules/graphql && ../../vendor/bin/phpstan analyse
+          if [[ ${{ matrix.phpstan }} == "1" ]]; then cd modules/graphql && ../../vendor/bin/phpstan analyse; fi
 
       - name: Run PHPCS
         run: |