feat(linter): load custom JS plugins

crates/oxc_linter/Cargo.toml

@@ -17,7 +17,7 @@ description.workspace = true
 default = []
 ruledocs = ["oxc_macros/ruledocs"] # Enables the `ruledocs` feature for conditional compilation
 language_server = ["oxc_data_structures/rope"] # For the Runtime to support needed information for the language server
-oxlint2 = []
+oxlint2 = ["tokio/rt-multi-thread"]
 disable_oxlint2 = []
 force_test_reporter = []
 
@@ -72,6 +72,7 @@ serde = { workspace = true, features = ["derive"] }
 serde_json = { workspace = true }
 simdutf8 = { workspace = true }
 smallvec = { workspace = true }
+tokio = { workspace = true }
 
 [dev-dependencies]
 insta = { workspace = true }

crates/oxc_linter/src/config/config_builder.rs

@@ -1,9 +1,10 @@
 use std::{
     fmt::{self, Debug, Display},
-    path::PathBuf,
+    path::{Path, PathBuf},
 };
 
 use itertools::Itertools;
+use oxc_resolver::{ResolveOptions, Resolver};
 use rustc_hash::FxHashMap;
 
 use oxc_span::{CompactStr, format_compact_str};
@@ -88,7 +89,7 @@ impl ConfigStoreBuilder {
     pub fn from_oxlintrc(
         start_empty: bool,
         oxlintrc: Oxlintrc,
-        _external_linter: Option<&ExternalLinter>,
+        external_linter: Option<&ExternalLinter>,
     ) -> Result<Self, ConfigBuilderError> {
         // TODO: this can be cached to avoid re-computing the same oxlintrc
         fn resolve_oxlintrc_config(
@@ -138,9 +139,14 @@ impl ConfigStoreBuilder {
         let (oxlintrc, extended_paths) = resolve_oxlintrc_config(oxlintrc)?;
 
         if let Some(plugins) = oxlintrc.plugins.as_ref() {
-            #[expect(clippy::never_loop)]
+            let resolver = oxc_resolver::Resolver::new(ResolveOptions::default());
             for plugin_name in &plugins.external {
-                return Err(ConfigBuilderError::UnknownPlugin(plugin_name.clone()));
+                Self::load_external_plugin(
+                    &oxlintrc.path,
+                    plugin_name,
+                    external_linter,
+                    &resolver,
+                )?;
             }
         }
         let plugins = oxlintrc.plugins.unwrap_or_default();
@@ -378,6 +384,53 @@ impl ConfigStoreBuilder {
         oxlintrc.rules = OxlintRules::new(new_rules);
         serde_json::to_string_pretty(&oxlintrc).unwrap()
     }
+
+    #[cfg(not(feature = "oxlint2"))]
+    fn load_external_plugin(
+        _oxlintrc_path: &Path,
+        _plugin_name: &str,
+        _external_linter: Option<&ExternalLinter>,
+        _resolver: &Resolver,
+    ) -> Result<(), ConfigBuilderError> {
+        Err(ConfigBuilderError::NoExternalLinterConfigured)
+    }
+
+    #[cfg(feature = "oxlint2")]
+    fn load_external_plugin(
+        oxlintrc_path: &Path,
+        plugin_name: &str,
+        external_linter: Option<&ExternalLinter>,
+        resolver: &Resolver,
+    ) -> Result<(), ConfigBuilderError> {
+        use crate::PluginLoadResult;
+        let Some(linter) = external_linter else {
+            return Err(ConfigBuilderError::NoExternalLinterConfigured);
+        };
+        let resolved =
+            resolver.resolve(oxlintrc_path.parent().unwrap(), plugin_name).map_err(|e| {
+                ConfigBuilderError::PluginLoadFailed {
+                    plugin_name: plugin_name.into(),
+                    error: e.to_string(),
+                }
+            })?;
+
+        let result = tokio::task::block_in_place(move || {
+            tokio::runtime::Handle::current()
+                .block_on((linter.load_plugin)(resolved.full_path().to_str().unwrap().to_string()))
+        })
+        .map_err(|e| ConfigBuilderError::PluginLoadFailed {
+            plugin_name: plugin_name.into(),
+            error: e.to_string(),
+        })?;
+
+        match result {
+            PluginLoadResult::Success => Ok(()),
+            PluginLoadResult::Failure(e) => Err(ConfigBuilderError::PluginLoadFailed {
+                plugin_name: plugin_name.into(),
+                error: e,
+            }),
+        }
+    }
 }
 
 fn get_name(plugin_name: &str, rule_name: &str) -> CompactStr {
@@ -418,7 +471,11 @@ pub enum ConfigBuilderError {
         file: String,
         reason: String,
     },
-    UnknownPlugin(String),
+    PluginLoadFailed {
+        plugin_name: String,
+        error: String,
+    },
+    NoExternalLinterConfigured,
 }
 
 impl Display for ConfigBuilderError {
@@ -438,8 +495,13 @@ impl Display for ConfigBuilderError {
             ConfigBuilderError::InvalidConfigFile { file, reason } => {
                 write!(f, "invalid config file {file}: {reason}")
             }
-            ConfigBuilderError::UnknownPlugin(plugin_name) => {
-                write!(f, "unknown plugin: {plugin_name}")
+            ConfigBuilderError::PluginLoadFailed { plugin_name, error } => {
+                write!(f, "Failed to load external plugin: {plugin_name}\n  {error}")?;
+                Ok(())
+            }
+            ConfigBuilderError::NoExternalLinterConfigured => {
+                f.write_str("Failed to load external plugin because no external linter was configured. This means the Oxlint binary was executed directly rather than via napi bindings.")?;
+                Ok(())
             }
         }
     }

napi/oxlint2/src/index.js

@@ -1,12 +1,27 @@
 import { lint } from './bindings.js';
 
 class Linter {
+  pluginRegistry = new Map();
+
   run() {
     return lint(this.loadPlugin.bind(this), this.lint.bind(this));
   }
 
-  loadPlugin = async (_pluginName) => {
-    throw new Error('unimplemented');
+  loadPlugin = async (pluginName) => {
+    if (this.pluginRegistry.has(pluginName)) {
+      return JSON.stringify({ Success: null });
+    }
+
+    try {
+      const plugin = await import(pluginName);
+      this.pluginRegistry.set(pluginName, plugin);
+      return JSON.stringify({ Success: null });
+    } catch (error) {
+      const errorMessage = 'message' in error && typeof error.message === 'string'
+        ? error.message
+        : 'An unknown error occurred';
+      return JSON.stringify({ Failure: errorMessage });
+    }
   };
 
   lint = async () => {

napi/oxlint2/test/__snapshots__/e2e.test.ts.snap

@@ -4,3 +4,16 @@ exports[`cli options for bundling > should lint a directory 1`] = `
 "Found 0 warnings and 0 errors.
 Finished in Xms on 0 files with 1 rules using X threads."
 `;
+
+exports[`cli options for bundling > should load a custom plugin 1`] = `
+"Found 0 warnings and 0 errors.
+Finished in Xms on 1 file using X threads."
+`;
+
+exports[`cli options for bundling > should report an error if a custom plugin cannot be loaded 1`] = `
+"Failed to parse configuration file.
+
+  x Failed to load external plugin: ./test_plugin
+  |   Cannot find module './test_plugin'
+"
+`;

napi/oxlint2/test/e2e.test.ts

@@ -27,4 +27,22 @@ describe('cli options for bundling', () => {
     expect(exitCode).toBe(0);
     expect(normalizeOutput(stdout)).toMatchSnapshot();
   });
+
+  it('should load a custom plugin', async () => {
+    const { stdout, exitCode } = await runOxlint(
+      'test/fixtures/basic_custom_plugin',
+    );
+
+    expect(exitCode).toBe(0);
+    expect(normalizeOutput(stdout)).toMatchSnapshot();
+  });
+
+  it('should report an error if a custom plugin cannot be loaded', async () => {
+    const { stdout, exitCode } = await runOxlint(
+      'test/fixtures/missing_custom_plugin',
+    );
+
+    expect(exitCode).toBe(1);
+    expect(normalizeOutput(stdout)).toMatchSnapshot();
+  });
 });

napi/oxlint2/test/fixtures/basic_custom_plugin/.oxlintrc.json

@@ -0,0 +1,5 @@
+{
+    "plugins": [
+        "./test_plugin"
+    ]
+}

napi/oxlint2/test/fixtures/basic_custom_plugin/test_plugin/index.js

@@ -0,0 +1,3 @@
+export default {
+  rules: {},
+};

napi/oxlint2/test/fixtures/missing_custom_plugin/.oxlintrc.json

@@ -0,0 +1,5 @@
+{
+    "plugins": [
+        "./test_plugin"
+    ]
+}

napi/playground/Cargo.toml

@@ -28,7 +28,7 @@ oxc_index = { workspace = true }
 oxc_linter = { workspace = true }
 oxc_napi = { workspace = true }
 
-napi = { workspace = true }
+napi = { workspace = true, features = ["async"] }
 napi-derive = { workspace = true }
 rustc-hash = { workspace = true }
 serde = { workspace = true }