Add dry-run (#270)

* Add dry-run

* Add dry-run test

* format

---------

Co-authored-by: Bartek Pacia <barpac02@gmail.com>

.github/workflows/workflow.yaml

@@ -28,6 +28,7 @@ jobs:
         operating-system:
           [ubuntu-latest, windows-latest, macos-latest, macos-13, macos-14]
         channel: [stable, beta, master]
+        dry-run: [true, false]
         include:
           - operating-system: ubuntu-latest
             channel: main
@@ -39,6 +40,7 @@ jobs:
         uses: ./
         with:
           channel: ${{ matrix.channel }}
+          dry-run: ${{ matrix.dry-run }}
       - name: Echo outputs
         run: |
           echo RUNNER-OS=${{ runner.os }}
@@ -51,8 +53,16 @@ jobs:
           echo ARCHITECTURE=${{ steps.flutter-action.outputs.ARCHITECTURE }}
         shell: bash
       - run: dart --version
+        if: ${{ matrix.dry-run != 'true' }}
         shell: bash
       - run: flutter --version
+        if: ${{ matrix.dry-run != 'true' }}
+        shell: bash
+      - run: "! dart --version"
+        if: ${{ matrix.dry-run == 'true' }}
+        shell: bash
+      - run: "! flutter --version"
+        if: ${{ matrix.dry-run == 'true' }}
         shell: bash
 
   test_cache:

README.md

@@ -282,6 +282,30 @@ steps:
       echo PUB-CACHE-KEY=${{ steps.flutter-action.outputs.PUB-CACHE-KEY }}
 ```
 
+If you don't need to install Flutter and just want the outputs, you can use the
+`dry-run` option:
+
+```yaml
+steps:
+  - name: Clone repository
+  - uses: actions/checkout@v4
+  - name: Set up Flutter
+    uses: subosito/flutter-action@v2
+    id: flutter-action
+    with:
+      channel: stable
+      dry-run: true
+  - run: |
+      echo CACHE-PATH=${{ steps.flutter-action.outputs.CACHE-PATH }}
+      echo CACHE-KEY=${{ steps.flutter-action.outputs.CACHE-KEY }}
+      echo CHANNEL=${{ steps.flutter-action.outputs.CHANNEL }}
+      echo VERSION=${{ steps.flutter-action.outputs.VERSION }}
+      echo ARCHITECTURE=${{ steps.flutter-action.outputs.ARCHITECTURE }}
+      echo PUB-CACHE-PATH=${{ steps.flutter-action.outputs.PUB-CACHE-PATH }}
+      echo PUB-CACHE-KEY=${{ steps.flutter-action.outputs.PUB-CACHE-KEY }}
+    shell: bash
+```
+
 ## Maintainers
 
 - [Alif Rachmawadi] (original creator)

action.yaml

@@ -42,6 +42,10 @@ inputs:
     description: Flutter pub cache path
     required: false
     default: default
+  dry-run:
+    description: If true, get outputs but do not install Flutter
+    required: false
+    default: "false"
 
 outputs:
   CHANNEL:
@@ -108,6 +112,7 @@ runs:
 
     - name: Run setup script
       shell: bash
+      if: ${{ inputs.dry-run != 'true' }}
       run: |
         $GITHUB_ACTION_PATH/setup.sh \
           -n '${{ steps.flutter-action.outputs.VERSION }}' \