fix: allow multistage Dockerfiles by removing AS <stage name> in validation

- Modified the validate_docker_compose_yml function to support multistage Dockerfiles.
- Updated the FROM line parsing to remove the AS <stage name> part for case-insensitive comparison.
- This ensures compatibility with Dockerfiles using multistage builds.

Author: Sainomori

connect/eaas/core/validation/validators/base.py

@@ -224,7 +224,7 @@ def validate_docker_compose_yml(context):  # noqa: CCR001
                     ),
                 )
                 continue
-            image = from_cmd[4:].strip()
+            image = re.sub(r'\s+AS\s+.*', '', from_cmd[4:], flags=re.IGNORECASE).strip()
             if image != runner_image:
                 messages.append(
                     ValidationItem(

tests/connect/eaas/core/validation/validators/test_base.py

@@ -566,6 +566,37 @@ def test_validate_docker_compose_yml_invalid_image_dockerfile(mocker):
     assert item.file == 'fake_dir/Dockerfile'
 
 
+def test_validate_docker_compose_yml_multistage_image_dockerfile(mocker):
+    mocker.patch(
+        'connect.eaas.core.validation.validators.base.os.path.isfile',
+        return_value=True,
+    )
+    mocked_open = mocker.MagicMock()
+    mocked_open.read.return_value = (
+        'FROM cloudblueconnect/connect-extension-runner:0.3 as a-stage-name\n'
+    )
+    mocker.patch(
+        'connect.eaas.core.validation.validators.base.open',
+        side_effect=[None, mocked_open],
+    )
+    mocker.patch(
+        'connect.eaas.core.validation.validators.base.yaml.safe_load',
+        return_value={
+            'services': {
+                'dev': {
+                    'build': {'dockerfile': 'Dockerfile'},
+                },
+            },
+        },
+    )
+
+    result = validate_docker_compose_yml({'project_dir': 'fake_dir', 'runner_version': '0.3'})
+
+    assert isinstance(result, ValidationResult)
+    assert result.must_exit is False
+    assert len(result.items) == 0
+
+
 def test_validate_docker_compose_yml_invalid_image_no_dockerfile(mocker):
     mocker.patch(
         'connect.eaas.core.validation.validators.base.os.path.isfile',