fix(linter): reverse extends overrides priority (#14939)

Fixes #14925

Author: wagenet

crates/oxc_linter/fixtures/extends_config/overrides/base_override.json

@@ -0,0 +1,10 @@
+{
+  "overrides": [
+    {
+      "files": ["*.test.ts"],
+      "rules": {
+        "no-const-assign": "error"
+      }
+    }
+  ]
+}

crates/oxc_linter/fixtures/extends_config/overrides/current_override.json

@@ -0,0 +1,11 @@
+{
+  "extends": ["./base_override.json"],
+  "overrides": [
+    {
+      "files": ["*.test.ts"],
+      "rules": {
+        "no-const-assign": "off"
+      }
+    }
+  ]
+}

crates/oxc_linter/src/config/config_builder.rs

@@ -137,7 +137,7 @@ impl ConfigStoreBuilder {
 
                 let (extends, extends_paths) = resolve_oxlintrc_config(extends_oxlintrc)?;
 
-                oxlintrc = oxlintrc.merge(extends);
+                oxlintrc = oxlintrc.merge(&extends);
                 extended_paths.extend(extends_paths);
             }
 
@@ -1240,6 +1240,44 @@ mod test {
         assert!(config.rules().is_empty());
     }
 
+    #[test]
+    fn test_extends_overrides_precedence() {
+        // Test that current config's overrides take priority over extended config's overrides
+        // This is consistent with how base-level rules work (current overrides extended)
+
+        // Load the oxlintrc that extends a base config
+        let current_oxlintrc = Oxlintrc::from_file(&PathBuf::from(
+            "fixtures/extends_config/overrides/current_override.json",
+        ))
+        .unwrap();
+
+        // Build the config with from_oxlintrc which will handle extends
+        let mut external_plugin_store = ExternalPluginStore::default();
+        let builder = ConfigStoreBuilder::from_oxlintrc(
+            false, // start_empty = false to get default rules
+            current_oxlintrc,
+            None,
+            &mut external_plugin_store,
+        )
+        .unwrap();
+
+        let config = builder.build(&external_plugin_store).unwrap();
+
+        // Apply overrides for a foo.test.ts file (matches both overrides)
+        let resolved = config.apply_overrides(Path::new("foo.test.ts"));
+
+        // The no-const-assign rule should be "off" (disabled, not present in rules)
+        // because current config's override sets it to "off", which should take priority
+        // over the extended config's override which sets it to "error"
+        let no_const_assign_rule =
+            resolved.rules.iter().find(|(rule, _)| rule.name() == "no-const-assign");
+
+        assert!(
+            no_const_assign_rule.is_none(),
+            "no-const-assign should be disabled (off) by current config's override, not error from extended config"
+        );
+    }
+
     fn config_store_from_path(path: &str) -> Config {
         let mut external_plugin_store = ExternalPluginStore::default();
         ConfigStoreBuilder::from_oxlintrc(

crates/oxc_linter/src/config/oxlintrc.rs

@@ -218,7 +218,7 @@ impl Oxlintrc {
     /// Merges two [Oxlintrc] files together
     /// [Self] takes priority over `other`
     #[must_use]
-    pub fn merge(&self, other: Oxlintrc) -> Oxlintrc {
+    pub fn merge(&self, other: &Oxlintrc) -> Oxlintrc {
         let mut categories = other.categories.clone();
         categories.extend(self.categories.iter());
 
@@ -242,8 +242,8 @@ impl Oxlintrc {
         let env = self.env.clone();
         let globals = self.globals.clone();
 
-        let mut overrides = self.overrides.clone();
-        overrides.extend(other.overrides);
+        let mut overrides = other.overrides.clone();
+        overrides.extend(self.overrides.clone());
 
         let plugins = match (self.plugins, other.plugins) {
             (Some(self_plugins), Some(other_plugins)) => Some(self_plugins | other_plugins),