feat: drop support for jiti v1.21 (#18996)

* feat: drop support for jiti v1.21

* fix for CommonJS TS config that exports undefined

docs/src/use/configure/configuration-files.md

@@ -529,7 +529,7 @@ npx eslint --flag unstable_ts_config
 
 For more information about using feature flags, see [Feature Flags](../../flags/).
 
-For Deno and Bun, TypeScript configuration files are natively supported; for Node.js, you must install the optional dev dependency [`jiti`](https://github.com/unjs/jiti) in your project (this dependency is not automatically installed by ESLint):
+For Deno and Bun, TypeScript configuration files are natively supported; for Node.js, you must install the optional dev dependency [`jiti`](https://github.com/unjs/jiti) in version 2.0.0 or later in your project (this dependency is not automatically installed by ESLint):
 
 ```bash
 npm install -D jiti

lib/config/config-loader.js

@@ -173,21 +173,22 @@ async function loadConfigFile(filePath, allowTS) {
      */
     if (allowTS && isTS && !isDeno && !isBun) {
 
-        const createJiti = await import("jiti").then(jitiModule => (typeof jitiModule?.createJiti === "function" ? jitiModule.createJiti : jitiModule.default), () => {
+        // eslint-disable-next-line no-use-before-define -- `ConfigLoader.loadJiti` can be overwritten for testing
+        const { createJiti } = await ConfigLoader.loadJiti().catch(() => {
             throw new Error("The 'jiti' library is required for loading TypeScript configuration files. Make sure to install it.");
         });
 
+        // `createJiti` was added in jiti v2.
+        if (typeof createJiti !== "function") {
+            throw new Error("You are using an outdated version of the 'jiti' library. Please update to the latest version of 'jiti' to ensure compatibility and access to the latest features.");
+        }
+
         /*
          * Disabling `moduleCache` allows us to reload a
          * config file when the last modified timestamp changes.
          */
 
         const jiti = createJiti(__filename, { moduleCache: false, interopDefault: false });
-
-        if (typeof jiti?.import !== "function") {
-            throw new Error("You are using an outdated version of the 'jiti' library. Please update to the latest version of 'jiti' to ensure compatibility and access to the latest features.");
-        }
-
         const config = await jiti.import(fileURL.href);
 
         importedConfigFileModificationTime.set(filePath, mtime);
@@ -294,7 +295,6 @@ async function calculateConfigArray(configFilePath, basePath, options) {
     return configs;
 }
 
-
 //-----------------------------------------------------------------------------
 // Exports
 //-----------------------------------------------------------------------------
@@ -517,6 +517,15 @@ class ConfigLoader {
         return this.#configArrays.get(configFilePath);
     }
 
+    /**
+     * Used to import the jiti dependency. This method is exposed internally for testing purposes.
+     * @returns {Promise<Record<string, unknown>>} A promise that fulfills with a module object
+     *      or rejects with an error if jiti is not found.
+     */
+    static loadJiti() {
+        return import("jiti");
+    }
+
 }
 
 /**

tests/fixtures/ts-config-files/ts/eslint.undefined.config.ts

@@ -0,0 +1 @@
+export = void 0;

tests/lib/eslint/eslint.js

@@ -1313,6 +1313,61 @@ describe("ESLint", () => {
 
                 });
 
+                it("should fail to load a TS config file if jiti is not installed", async () => {
+
+                    const { ConfigLoader } = require("../../../lib/config/config-loader");
+
+                    sinon.stub(ConfigLoader, "loadJiti").rejects();
+
+                    const cwd = getFixturePath("ts-config-files", "ts");
+
+                    eslint = new ESLint({
+                        cwd,
+                        flags: tsFlags
+                    });
+
+                    await assert.rejects(
+                        eslint.lintText("foo();"),
+                        { message: "The 'jiti' library is required for loading TypeScript configuration files. Make sure to install it." }
+                    );
+                });
+
+                it("should fail to load a TS config file if an outdated version of jiti is installed", async () => {
+
+                    const { ConfigLoader } = require("../../../lib/config/config-loader");
+
+                    sinon.stub(ConfigLoader, "loadJiti").resolves({});
+
+                    const cwd = getFixturePath("ts-config-files", "ts");
+
+                    eslint = new ESLint({
+                        cwd,
+                        flags: tsFlags
+                    });
+
+                    await assert.rejects(
+                        eslint.lintText("foo();"),
+                        { message: "You are using an outdated version of the 'jiti' library. Please update to the latest version of 'jiti' to ensure compatibility and access to the latest features." }
+                    );
+                });
+
+                it("should fail to load a CommonJS TS config file that exports undefined with a helpful error message", async () => {
+
+                    const cwd = getFixturePath("ts-config-files", "ts");
+
+                    eslint = new ESLint({
+                        cwd,
+                        flags: tsFlags,
+                        overrideConfigFile: "eslint.undefined.config.ts"
+                    });
+
+                    await assert.rejects(
+                        eslint.lintText("foo"),
+                        { message: "Config (unnamed): Unexpected undefined config at user-defined index 0." }
+                    );
+
+                });
+
             });
 
             it("should pass BOM through processors", async () => {
@@ -5753,6 +5808,61 @@ describe("ESLint", () => {
 
                 });
 
+                it("should fail to load a TS config file if jiti is not installed", async () => {
+
+                    const { ConfigLoader } = require("../../../lib/config/config-loader");
+
+                    sinon.stub(ConfigLoader, "loadJiti").rejects();
+
+                    const cwd = getFixturePath("ts-config-files", "ts");
+
+                    eslint = new ESLint({
+                        cwd,
+                        flags: newFlags
+                    });
+
+                    await assert.rejects(
+                        eslint.lintFiles("foo.js"),
+                        { message: "The 'jiti' library is required for loading TypeScript configuration files. Make sure to install it." }
+                    );
+                });
+
+                it("should fail to load a TS config file if an outdated version of jiti is installed", async () => {
+
+                    const { ConfigLoader } = require("../../../lib/config/config-loader");
+
+                    sinon.stub(ConfigLoader, "loadJiti").resolves({});
+
+                    const cwd = getFixturePath("ts-config-files", "ts");
+
+                    eslint = new ESLint({
+                        cwd,
+                        flags: newFlags
+                    });
+
+                    await assert.rejects(
+                        eslint.lintFiles("foo.js"),
+                        { message: "You are using an outdated version of the 'jiti' library. Please update to the latest version of 'jiti' to ensure compatibility and access to the latest features." }
+                    );
+                });
+
+                it("should fail to load a CommonJS TS config file that exports undefined with a helpful error message", async () => {
+
+                    const cwd = getFixturePath("ts-config-files", "ts");
+
+                    eslint = new ESLint({
+                        cwd,
+                        flags: newFlags,
+                        overrideConfigFile: "eslint.undefined.config.ts"
+                    });
+
+                    await assert.rejects(
+                        eslint.lintFiles("foo.js"),
+                        { message: "Config (unnamed): Unexpected undefined config at user-defined index 0." }
+                    );
+
+                });
+
             });
 
             it("should stop linting files if a rule crashes", async () => {