Correct behavior of EXTENDS (#1516)

Ensure that local config keys overwrite inherited config keys rather
than the other way around.

CHANGELOG.md

@@ -10,9 +10,10 @@ Note: Can be used with `oxsecurity/megalinter@beta` in your GitHub Action mega-l
 
 - Replace `set-output` usage with `GITHUB_OUTPUT`
 - New MegaLinter plugin: [mustache](https://github.com/one-acre-fund/mega-linter-plugin-logstash): Plugin to validate [Logstash](https://www.elastic.co/guide/en/logstash/current/configuration.html) pipeline definition files using [mustache](https://github.com/breml/logstash-config), by [Yann Jouanique](https://github.com/Yann-J)
-
+- Correct behavior of `EXTENDS` ([#1516](https://github.com/oxsecurity/megalinter/issues/1516))
 - Add the SPELL_*_FILE_EXTENSIONS parameter for each SPELL type linter. If set, it will use this value to filter instead of the default behavior which is to parse the files of all other linters executed ([#1997](https://github.com/oxsecurity/megalinter/issues/1997)).
 
+
 - Linter versions upgrades
   - [djlint](https://djlint.com/) from 1.19.2 to **1.0.3** on 2022-10-24
   - [eslint-plugin-jsonc](https://ota-meshi.github.io/eslint-plugin-jsonc/) from 2.4.0 to **2.5.0** on 2022-10-24

megalinter/config.py

@@ -71,6 +71,7 @@ def init_config(workspace=None):
         )
     # manage EXTENDS in configuration
     if "EXTENDS" in runtime_config:
+        combined_config = {}
         extends = runtime_config["EXTENDS"]
         if isinstance(extends, str):
             extends = extends.split(",")
@@ -80,8 +81,10 @@ def init_config(workspace=None):
                 r.status_code == 200
             ), f"Unable to retrieve EXTENDS config file {config_file_name}"
             extends_config_data = yaml.safe_load(r.content)
-            runtime_config.update(extends_config_data)
+            combined_config.update(extends_config_data)
             CONFIG_SOURCE += f"\n[config] - extends from: {extends_item}"
+        combined_config.update(runtime_config)
+        runtime_config = combined_config
     # Print & set config in cache
     print(f"[config] {CONFIG_SOURCE}")
     set_config(runtime_config)

megalinter/tests/test_megalinter/config_test.py

@@ -49,7 +49,7 @@ def test_remote_config_extends_success(self):
         remote_config = self.test_folder + "base.mega-linter.yml"
         os.environ["MEGALINTER_CONFIG"] = remote_config
         config.init_config()
-        self.assertEqual("(extension1)", config.get("FILTER_REGEX_INCLUDE"))
+        self.assertEqual("(base)", config.get("FILTER_REGEX_INCLUDE"))
         self.assertEqual("(extension2)", config.get("FILTER_REGEX_EXCLUDE"))
         self.assertEqual("true", config.get("SHOW_ELAPSED_TIME"))