fix: Fix registries deletion when adding new ecosystems to dependabot.yml

dependabot_file.py

@@ -11,7 +11,6 @@
 # Define data structure for dependabot.yaml
 data = {
     "version": 2,
-    "registries": {},
     "updates": [],
 }
 
@@ -60,8 +59,6 @@ def make_dependabot_config(
             dependabot_config["updates"][-1].update(
                 {"registries": [SingleQuotedScalarString(ecosystem)]}
             )
-    else:
-        dependabot_config.pop("registries", None)
 
     if schedule_day:
         dependabot_config["updates"][-1].update(

test_dependabot_file.py

@@ -819,6 +819,56 @@ def test_build_dependabot_file_with_labels(self):
             )
             self.assertEqual(result, expected_result)
 
+    def test_build_dependabot_file_preserves_existing_registries(self):
+        """Test that existing registries are preserved when adding new ecosystems"""
+        repo = MagicMock()
+        repo.file_contents.side_effect = lambda filename: filename == "Gemfile"
+
+        # Create existing config with registries but no bundler ecosystem
+        existing_config = MagicMock()
+        existing_config.content = base64.b64encode(
+            b"""
+version: 2
+registries:
+  gradle-artifactory:
+    type: maven-repository
+    url: https://acme.jfrog.io/artifactory/my-gradle-registry
+    username: octocat
+    password: ${{secrets.MY_ARTIFACTORY_PASSWORD}}
+updates:
+  - package-ecosystem: "npm"
+    directory: "/"
+    schedule:
+      interval: "weekly"
+"""
+        )
+
+        expected_result = yaml.load(
+            b"""
+version: 2
+registries:
+  gradle-artifactory:
+    type: maven-repository
+    url: https://acme.jfrog.io/artifactory/my-gradle-registry
+    username: octocat
+    password: ${{secrets.MY_ARTIFACTORY_PASSWORD}}
+updates:
+  - package-ecosystem: "npm"
+    directory: "/"
+    schedule:
+      interval: "weekly"
+  - package-ecosystem: 'bundler'
+    directory: '/'
+    schedule:
+      interval: 'weekly'
+"""
+        )
+
+        result = build_dependabot_file(
+            repo, False, [], {}, existing_config, "weekly", "", [], None
+        )
+        self.assertEqual(result, expected_result)
+
 
 if __name__ == "__main__":
     unittest.main()