feat: adapt to new eslint flat config (#277)

lib/caches.js

@@ -38,12 +38,17 @@ async function getCache(cwd, eslint_path_arg) {
 }
 
 function createCache(cwd, eslint_path_arg) {
-  const absolute_eslint_path = eslint_path.resolve(cwd, eslint_path_arg);
+  let absolute_eslint_path = eslint_path.resolve(cwd, eslint_path_arg);
 
   if (!absolute_eslint_path) {
     return null;
   }
 
+  // Use new ESLintFlatConfig
+  if (process.env.ESLINT_USE_FLAT_CONFIG) {
+    absolute_eslint_path
+      = absolute_eslint_path.replace('/lib/api.js', '/lib/unsupported-api.js');
+  }
   return lru_cache.set(cwd, {
     eslint: require(absolute_eslint_path),
     // use chalk from eslint

lib/linter.js

@@ -80,6 +80,23 @@ function translateOptionsESLint(cliOptions, cwd) {
   };
 }
 
+function translateOptionsFlatESLint(cliOptions, cwd) {
+  return {
+    allowInlineConfig: cliOptions.inlineConfig,
+    cache: cliOptions.cache,
+    cacheLocation: cliOptions.cacheLocation || cliOptions.cacheFile,
+    cacheStrategy: cliOptions.cacheStrategy,
+    errorOnUnmatchedPattern: cliOptions.errorOnUnmatchedPattern,
+    fix: cliOptions.fix || cliOptions.fixDryRun || cliOptions.fixToStdout,
+    ignore: cliOptions.ignore,
+    plugins: cliOptions.plugin,
+    overrideConfigFile: cliOptions.config,
+    reportUnusedDisableDirectives: cliOptions.reportUnusedDisableDirectives
+      ? 'error' : undefined,
+    cwd
+  };
+}
+
 function countErrors(results) {
   let errorCount = 0;
   let warningCount = 0;
@@ -148,8 +165,15 @@ async function printResults(engine, results, opts, callback) {
   callback(null, output);
 }
 
-async function executeWithESLint(ESLint, cwd, opts, text, callback) {
-  const engine = new ESLint(translateOptionsESLint(opts, cwd));
+async function executeWithESLint(
+    ESLint,
+    cwd,
+    translateOptions,
+    opts,
+    text,
+    callback
+) {
+  const engine = new ESLint(translateOptions(opts, cwd));
   const files = opts._;
   const stdin = opts.stdin;
 
@@ -304,11 +328,16 @@ exports.invoke = async function (cwd, args, text, callback) {
     return;
   }
 
-  if (cache.eslint.ESLint) {
+  if (cache.eslint.ESLint || cache.eslint.FlatESLint) {
     const absolute_cwd = path.resolve(cwd);
     try {
-      await executeWithESLint(cache.eslint.ESLint, absolute_cwd, opts, text,
-        callback);
+      if (process.env.ESLINT_USE_FLAT_CONFIG) {
+        await executeWithESLint(cache.eslint.FlatESLint, absolute_cwd,
+          translateOptionsFlatESLint, opts, text, callback);
+      } else {
+        await executeWithESLint(cache.eslint.ESLint, absolute_cwd,
+          translateOptionsESLint, opts, text, callback);
+      }
     } catch (e) {
       e.exitCode = 2;
       callback(e);

test/fixture/eslint.config.js

@@ -0,0 +1,10 @@
+'use strict';
+
+module.exports = [
+  {
+    rules: {
+      semi: 'error',
+      'prefer-const': 'error'
+    }
+  }
+];

test/flat-config-test.js

@@ -0,0 +1,58 @@
+/*eslint-env mocha*/
+'use strict';
+
+const { assert } = require('@sinonjs/referee-sinon');
+const api = require('eslint');
+const unsupported = require('../node_modules/eslint/lib/unsupported-api');
+const caches = require('../lib/caches');
+const linter = require('../lib/linter');
+
+describe('flat-config', () => {
+
+  beforeEach(() => {
+    caches.lru_cache.clear();
+    delete process.env.ESLINT_USE_FLAT_CONFIG;
+  });
+  afterEach(() => {
+    caches.lru_cache.clear();
+    delete process.env.ESLINT_USE_FLAT_CONFIG;
+  });
+
+  describe('without flat config', () => {
+    it('resolves ESLint class', async () => {
+      const cache = await caches.getCache(process.cwd());
+
+      assert.equals(typeof cache.eslint.ESLint, typeof api.ESLint);
+      assert.isUndefined(cache.eslint.FlatESLint);
+    });
+
+    it('runs lint with ESLint class', async () => {
+      await linter.invoke(process.cwd(), ['.'], undefined, () => null);
+    });
+  });
+
+  describe('with flat configV', () => {
+    it('resolves FlatESLint class', async () => {
+      process.env.ESLINT_USE_FLAT_CONFIG = 'true';
+
+      const cache = await caches.getCache(process.cwd());
+
+      assert.equals(
+        typeof cache.eslint.FlatESLint,
+        typeof unsupported.FlatESLint
+      );
+      assert.isUndefined(cache.eslint.ESLint);
+    });
+
+    it('runs lint with FlatESLint class', async () => {
+      process.env.ESLINT_USE_FLAT_CONFIG = 'true';
+
+      await linter.invoke(
+        process.cwd(),
+        ['-c', `${process.cwd()}/test/fixture/eslint.config.js`],
+        undefined,
+        () => null
+      );
+    });
+  });
+});