Use jiti.import + add tests

packages/knip/fixtures/load-cjs/package.json

@@ -0,0 +1,4 @@
+{
+  "name": "@fixtures/load-cjs",
+  "type": "commonjs"
+}

packages/knip/fixtures/load-esm-ts/index.ts

@@ -0,0 +1,22 @@
+// SyntaxError: Cannot use 'import.meta' outside a module
+
+import.meta;
+import.meta.resolve;
+import.meta.url;
+
+// SyntaxError: Unexpected identifier 'Promise'
+
+Promise;
+
+// TypeError: Reflect.metadata is not a function
+
+function meow(target: unknown, _: unknown) {}
+
+@meow
+export class Cat {
+  constructor() {}
+}
+
+// SyntaxError: await is only valid in async functions and the top level bodies of modules
+
+await Promise.resolve('TLA');

packages/knip/fixtures/load-esm-ts/package.json

@@ -0,0 +1,4 @@
+{
+  "name": "@fixtures/load-esm-ts",
+  "type": "module"
+}

packages/knip/fixtures/load-esm-ts/tsconfig.json

@@ -0,0 +1,7 @@
+{
+  "compilerOptions": {
+    "module": "esnext",
+    "experimentalDecorators": true,
+    "emitDecoratorMetadata": true
+  }
+}

packages/knip/fixtures/load-esm/index.js

@@ -0,0 +1,18 @@
+// The CJS build of Vite's Node API is deprecated. See https://vitejs.dev/guide/troubleshooting.html#vite-cjs-node-api-deprecated for more details.
+
+// SyntaxError: Cannot use 'import.meta' outside a module
+
+import.meta;
+import.meta.resolve;
+import.meta.url;
+
+// SyntaxError: await is only valid in async functions and the top level bodies of modules
+
+// SyntaxError: missing ) after argument list
+
+// SyntaxError: Unexpected identifier 'Promise'
+Promise;
+
+// Error [ERR_PACKAGE_PATH_NOT_EXPORTED]: No "exports" main defined in [...]/node_modules/estree-walker/package.json
+
+await Promise.resolve('TLA');

packages/knip/fixtures/load-esm/package.json

@@ -0,0 +1,4 @@
+{
+  "name": "@fixtures/load-esm",
+  "type": "module"
+}

packages/knip/src/util/fs.ts

@@ -1,11 +1,11 @@
-import { readFileSync, statSync } from 'node:fs';
+import { statSync } from 'node:fs';
 import { readFile } from 'node:fs/promises';
 import yaml from 'js-yaml';
 import { parse as parseTOML } from 'smol-toml';
 import stripJsonComments from 'strip-json-comments';
 import { timerify } from './Performance.js';
 import { LoaderError } from './errors.js';
-import { dirname, join } from './path.js';
+import { join } from './path.js';
 
 export const isDirectory = (filePath: string) => {
   try {
@@ -64,18 +64,4 @@ export const parseYAML = (contents: string) => {
   return yaml.load(contents);
 };
 
-export function isTypeModule(path: string) {
-  while (path && path !== '.' && path !== '/') {
-    path = dirname(path);
-    try {
-      const pkg = readFileSync(join(path, 'package.json'), 'utf-8');
-      try {
-        return JSON.parse(pkg).type === 'module';
-      } catch {}
-      break;
-    } catch {}
-  }
-  return false;
-}
-
 export const _loadJSON = timerify(loadJSON);

packages/knip/src/util/loader.ts

@@ -1,8 +1,6 @@
-import { pathToFileURL } from 'node:url';
 import { timerify } from './Performance.js';
 import { LoaderError } from './errors.js';
 import { loadFile, loadJSON, loadTOML, loadYAML, parseJSON, parseYAML } from './fs.js';
-import { isTypeModule } from './fs.js';
 import { jiti } from './jiti.js';
 import { extname, isInternal } from './path.js';
 
@@ -39,13 +37,7 @@ const load = async (filePath: string) => {
       return await loadTOML(filePath);
     }
 
-    if (ext === '.mjs' || (ext === '.js' && isTypeModule(filePath))) {
-      const fileUrl = pathToFileURL(filePath);
-      const imported = await import(fileUrl.href);
-      return imported.default ?? imported;
-    }
-
-    return await jiti(filePath);
+    return await jiti.import(filePath);
   } catch (error) {
     throw new LoaderError(`Error loading ${filePath}`, { cause: error });
   }

packages/knip/test/util/load.test.ts

@@ -0,0 +1,19 @@
+import { test } from 'bun:test';
+import assert from 'node:assert/strict';
+import { _load as load } from '../../src/util/loader.js';
+import { join, resolve } from '../../src/util/path.js';
+
+test('Should load modules (CommonJS)', async () => {
+  const cwd = resolve('fixtures/load-cjs');
+  await assert.doesNotReject(load(join(cwd, 'index.js')));
+});
+
+test('Should load modules (ESM)', async () => {
+  const cwd = resolve('fixtures/load-esm');
+  await assert.doesNotReject(load(join(cwd, 'index.js')));
+});
+
+test('Should load modules (ESM/TS)', async () => {
+  const cwd = resolve('fixtures/load-esm-ts');
+  await assert.doesNotReject(load(join(cwd, 'index.ts')));
+});