Chores: Replace CLIEngine with ESLint class. (#1608)

tests/eslint-compat.js

@@ -0,0 +1,56 @@
+// @ts-check
+const eslint = require('eslint')
+
+module.exports = {
+  ESLint: eslint.ESLint || getESLintClassForV6(),
+  RuleTester: eslint.RuleTester
+}
+
+/** @returns {typeof eslint.ESLint} */
+function getESLintClassForV6() {
+  class ESLintForV6 {
+    static get version() {
+      return eslint.CLIEngine.version
+    }
+
+    /** @param {eslint.ESLint.Options} options */
+    constructor(options) {
+      const {
+        overrideConfig: { plugins, globals, ...overrideConfig },
+        fix,
+        reportUnusedDisableDirectives,
+        plugins: pluginsMap,
+        ...otherOptions
+      } = options
+      this.engine = new eslint.CLIEngine({
+        fix: Boolean(fix),
+        globals: globals
+          ? Object.keys(globals).filter((n) => globals[n])
+          : undefined,
+        ...otherOptions,
+        ...overrideConfig,
+        plugins: plugins || [],
+        reportUnusedDisableDirectives: reportUnusedDisableDirectives
+          ? reportUnusedDisableDirectives !== 'off'
+          : undefined
+      })
+
+      for (const [name, plugin] of Object.entries(pluginsMap || {})) {
+        this.engine.addPlugin(name, plugin)
+      }
+    }
+
+    /**
+     * @param {Parameters<eslint.ESLint['lintText']>} params
+     * @returns {ReturnType<eslint.ESLint['lintText']>}
+     */
+    async lintText(...params) {
+      const result = this.engine.executeOnText(params[0], params[1].filePath)
+      return result.results
+    }
+  }
+
+  /** @type {typeof eslint.ESLint} */
+  const eslintClass = /** @type {any} */ (ESLintForV6)
+  return eslintClass
+}