fix: handle invalid YAML in existing dependabot config gracefully

dependabot_file.py

@@ -251,7 +251,7 @@ def build_dependabot_file(
             dependabot_file = yaml.load(base64.b64decode(existing_config.content))
         except ruamel.yaml.YAMLError as e:
             print(f"YAML indentation error: {e}")
-            raise
+            print(f"YAML parsing error in existing dependabot config: {e}")
     else:
         dependabot_file = copy.deepcopy(data)
 

evergreen.py

@@ -178,6 +178,10 @@ def main():  # pragma: no cover
             cooldown,
         )
 
+        if dependabot_file is None:
+            print("\tNo (new) compatible package manager found")
+            continue
+
         yaml = ruamel.yaml.YAML()
         stream = io.StringIO()
         yaml.indent(mapping=2, sequence=4, offset=2)
@@ -186,10 +190,6 @@ def main():  # pragma: no cover
         with open("dependabot-output.yaml", "w", encoding="utf-8") as yaml_file:
             yaml.dump(dependabot_file, yaml_file)
 
-        if dependabot_file is None:
-            print("\tNo (new) compatible package manager found")
-            continue
-
         dependabot_file = yaml.dump(dependabot_file, stream)
         dependabot_file = stream.getvalue()
 

test_dependabot_file.py

@@ -131,6 +131,29 @@ def test_build_dependabot_file_with_2_space_indent_existing_config_bundler_with_
         )
         self.assertEqual(result, expected_result)
 
+    def test_build_dependabot_file_with_duplicate_key_in_existing_config(self):
+        """Test that a duplicate key in existing dependabot config returns None instead of crashing"""
+        repo = MagicMock()
+        repo.file_contents.side_effect = lambda f, filename="Gemfile": f == filename
+
+        existing_config = MagicMock()
+        existing_config.content = base64.b64encode(b"""
+version: 2
+updates:
+  - package-ecosystem: "maven"
+    directory: "/"
+    schedule:
+      interval: "daily"
+    schedule:
+      interval: "weekly"
+      day: "friday"
+""")
+
+        result = build_dependabot_file(
+            repo, False, [], {}, existing_config, "weekly", "", [], None
+        )
+        self.assertIsNone(result)
+
     def test_build_dependabot_file_with_weird_space_indent_existing_config_bundler_with_update(
         self,
     ):
@@ -152,10 +175,10 @@ def test_build_dependabot_file_with_weird_space_indent_existing_config_bundler_w
     prefix: "chore(deps)"
   """)
 
-        with self.assertRaises(ruamel.yaml.YAMLError):
-            build_dependabot_file(
-                repo, False, [], {}, existing_config, "weekly", "", [], None
-            )
+        result = build_dependabot_file(
+            repo, False, [], {}, existing_config, "weekly", "", [], None
+        )
+        self.assertIsNone(result)
 
     def test_build_dependabot_file_with_incorrect_indentation_in_extra_dependabot_config_file(
         self,