Fix pipeline by storing artifact

.github/workflows/build.yml

@@ -1,5 +1,16 @@
 on:
   workflow_call:
+    inputs:
+      store-artifact:
+        description: 'Whether the built artifact should be stored'
+        default: false
+        required: false
+        type: boolean
+      artifact-name:
+        description: 'Name of the artifact, defaults to `built-app`'
+        default: built-app
+        required: false
+        type: string
 
 jobs:
   build:
@@ -14,4 +25,11 @@ jobs:
       - name: Install dependencies
         run: npm ci
       - name: Build app
-        run: npm run build
+        run: npm run build
+      - name: Archive build artifacts
+        if: ${{ inputs.store-artifact }}
+        uses: actions/upload-artifact@v2
+        with:
+          name: ${{ inputs.artifact-name }}
+          path: ./build
+          retention-days: 3 # we only store these for 3 days because they're almost always immediately used

.github/workflows/deploy.yml

@@ -4,10 +4,19 @@ on:
   push:
     branches:
       - main
+      - feature/fix-pipeline-empty # todo: only for testing
+
+env:
+  ARTIFACT_NAME: built-app
+  BUILD_DIRECTORY: ./build
+
 jobs:
   build:
     name: Check Build
     uses: ./.github/workflows/build.yml
+    with:
+      store-artifact: true
+      artifact-name: $ARTIFACT_NAME
 
   deploy:
     permissions:
@@ -17,8 +26,13 @@ jobs:
     name: Deploy to GitHub Pages
     runs-on: ubuntu-latest
     steps:
+      - name: Download artifact
+        uses: actions/download-artifact@v2
+        with:
+          name: $ARTIFACT_NAME
+          path: $BUILD_DIRECTORY
       - name: Deploy to GitHub Pages
         uses: peaceiris/actions-gh-pages@v3
         with:
           github_token: ${{ secrets.GITHUB_TOKEN }}
-          publish_dir: ./build
+          publish_dir: $BUILD_DIRECTORY