fix(linter/plugins): output warning on first JS plugin load

Author: overlookmotel

apps/oxlint/src/lint.rs

@@ -238,13 +238,6 @@ impl CliRunner {
         let mut external_linter = self.external_linter;
         if external_plugin_store.is_empty() {
             external_linter = None;
-        } else {
-            #[expect(clippy::print_stderr)]
-            {
-                eprintln!(
-                    "WARNING: JS plugins are experimental and not subject to semver.\nBreaking changes are possible while JS plugins support is under development."
-                );
-            }
         }
 
         if let Some(basic_config_file) = oxlintrc_for_print {

apps/oxlint/test/fixtures/custom_plugin_import_error/output.snap.md

@@ -12,4 +12,6 @@ Failed to parse configuration file.
 
 # stderr
 ```
+WARNING: JS plugins are experimental and not subject to semver.
+Breaking changes are possible while JS plugins support is under development.
 ```

apps/oxlint/test/fixtures/custom_plugin_lint_createOnce_error/output.snap.md

@@ -12,4 +12,6 @@ Failed to parse configuration file.
 
 # stderr
 ```
+WARNING: JS plugins are experimental and not subject to semver.
+Breaking changes are possible while JS plugins support is under development.
 ```

apps/oxlint/test/fixtures/custom_plugin_missing_rule/output.snap.md

@@ -10,4 +10,6 @@ Failed to parse configuration file.
 
 # stderr
 ```
+WARNING: JS plugins are experimental and not subject to semver.
+Breaking changes are possible while JS plugins support is under development.
 ```

apps/oxlint/test/fixtures/custom_plugin_via_overrides_missing_rule/output.snap.md

@@ -10,4 +10,6 @@ Failed to build configuration.
 
 # stderr
 ```
+WARNING: JS plugins are experimental and not subject to semver.
+Breaking changes are possible while JS plugins support is under development.
 ```

apps/oxlint/test/fixtures/missing_custom_plugin/output.snap.md

@@ -11,4 +11,6 @@ Failed to parse configuration file.
 
 # stderr
 ```
+WARNING: JS plugins are experimental and not subject to semver.
+Breaking changes are possible while JS plugins support is under development.
 ```

crates/oxc_linter/src/config/config_builder.rs

@@ -499,6 +499,14 @@ impl ConfigStoreBuilder {
     ) -> Result<(), ConfigBuilderError> {
         use crate::PluginLoadResult;
 
+        // Print warning on 1st attempt to load a plugin
+        #[expect(clippy::print_stderr)]
+        if external_plugin_store.is_empty() {
+            eprintln!(
+                "WARNING: JS plugins are experimental and not subject to semver.\nBreaking changes are possible while JS plugins support is under development."
+            );
+        }
+
         let resolved = resolver.resolve(oxlintrc_dir_path, plugin_specifier).map_err(|e| {
             ConfigBuilderError::PluginLoadFailed {
                 plugin_specifier: plugin_specifier.to_string(),