refactor(core): extract loader fs package

packages/core/package.json

@@ -41,6 +41,7 @@
   "dependencies": {
     "@eggjs/extend2": "workspace:*",
     "@eggjs/koa": "workspace:*",
+    "@eggjs/loader-fs": "workspace:*",
     "@eggjs/path-matching": "workspace:*",
     "@eggjs/router": "workspace:*",
     "@eggjs/typings": "workspace:*",

packages/core/src/index.ts

@@ -11,7 +11,7 @@ export * from './singleton.ts';
 export * from './loader/egg_loader.ts';
 export * from './loader/file_loader.ts';
 export * from './loader/context_loader.ts';
-export * from './loader/loader_fs.ts';
+export * from '@eggjs/loader-fs';
 export * from './loader/manifest.ts';
 export * from './utils/sequencify.ts';
 export * from './utils/timing.ts';

packages/core/src/loader/egg_loader.ts

@@ -5,6 +5,7 @@ import { debuglog, inspect } from 'node:util';
 
 import { extend } from '@eggjs/extend2';
 import { Request, Response, Application, Context as KoaContext } from '@eggjs/koa';
+import { RealLoaderFS, type LoaderFS } from '@eggjs/loader-fs';
 import { pathMatching, type PathMatchingOptions } from '@eggjs/path-matching';
 import { isESM, isSupportTypeScript } from '@eggjs/utils';
 import type { Logger } from 'egg-logger';
@@ -24,7 +25,6 @@ import { sequencify } from '../utils/sequencify.ts';
 import { Timing } from '../utils/timing.ts';
 import { type ContextLoaderOptions, ContextLoader } from './context_loader.ts';
 import { type FileLoaderOptions, CaseStyle, FULLPATH, FileLoader } from './file_loader.ts';
-import { RealLoaderFS, type LoaderFS } from './loader_fs.ts';
 import { ManifestStore, type StartupManifest } from './manifest.ts';
 
 const debug = debuglog('egg/core/loader/egg_loader');

packages/core/src/loader/file_loader.ts

@@ -2,11 +2,11 @@ import assert from 'node:assert';
 import path from 'node:path';
 import { debuglog } from 'node:util';
 
+import { RealLoaderFS, type LoaderFS } from '@eggjs/loader-fs';
 import { isSupportTypeScript } from '@eggjs/utils';
 import { isClass, isGeneratorFunction, isAsyncFunction, isPrimitive } from 'is-type-of';
 
 import utils from '../utils/index.ts';
-import { RealLoaderFS, type LoaderFS } from './loader_fs.ts';
 import type { ManifestStore } from './manifest.ts';
 
 const debug = debuglog('egg/core/file_loader');

packages/core/test/loader/file_loader.test.ts

@@ -1,12 +1,12 @@
 import assert from 'node:assert/strict';
 import path from 'node:path';
 
+import { RealLoaderFS, type LoaderFSGlobOptions } from '@eggjs/loader-fs';
 import { isClass } from 'is-type-of';
 import yaml from 'js-yaml';
 import { describe, it, expect } from 'vitest';
 
 import { FileLoader, CaseStyle } from '../../src/loader/file_loader.ts';
-import { RealLoaderFS, type LoaderFSGlobOptions } from '../../src/loader/loader_fs.ts';
 import { ManifestStore } from '../../src/loader/manifest.ts';
 import { getFilepath } from '../helper.ts';
 

packages/loader-fs/package.json

@@ -0,0 +1,51 @@
+{
+  "name": "@eggjs/loader-fs",
+  "version": "1.0.0-beta.9",
+  "description": "Loader-facing filesystem boundary for Egg loaders",
+  "keywords": [
+    "egg",
+    "filesystem",
+    "loader"
+  ],
+  "homepage": "https://github.com/eggjs/egg/tree/next/packages/loader-fs",
+  "license": "MIT",
+  "author": "fengmk2 <fengmk2@gmail.com>",
+  "repository": {
+    "type": "git",
+    "url": "git+https://github.com/eggjs/egg.git",
+    "directory": "packages/loader-fs"
+  },
+  "files": [
+    "dist"
+  ],
+  "type": "module",
+  "main": "./dist/index.js",
+  "module": "./dist/index.js",
+  "types": "./dist/index.d.ts",
+  "exports": {
+    ".": "./src/index.ts",
+    "./package.json": "./package.json"
+  },
+  "publishConfig": {
+    "access": "public",
+    "exports": {
+      ".": "./dist/index.js",
+      "./package.json": "./package.json"
+    }
+  },
+  "scripts": {
+    "typecheck": "tsgo --noEmit"
+  },
+  "dependencies": {
+    "@eggjs/utils": "workspace:*",
+    "globby": "catalog:",
+    "utility": "catalog:"
+  },
+  "devDependencies": {
+    "@eggjs/tsconfig": "workspace:*",
+    "typescript": "catalog:"
+  },
+  "engines": {
+    "node": ">=22.18.0"
+  }
+}

packages/loader-fs/src/index.ts

@@ -0,0 +1,73 @@
+import fs, { type Stats } from 'node:fs';
+import BuiltinModule from 'node:module';
+import path from 'node:path';
+import { debuglog } from 'node:util';
+
+import { importModule } from '@eggjs/utils';
+import globby from 'globby';
+import { readJSONSync } from 'utility';
+
+const debug = debuglog('egg/loader-fs');
+
+export type LoaderFSGlobOptions = globby.GlobbyOptions;
+
+export interface LoaderFS {
+  exists(filepath: string): boolean;
+  stat(filepath: string): Stats;
+  realpath(filepath: string): string;
+  readJSON<T = unknown>(filepath: string): T;
+  glob(patterns: string | string[], options?: LoaderFSGlobOptions): string[];
+  loadFile(filepath: string): Promise<unknown>;
+}
+
+interface ModuleConstructorWithExtensions {
+  _extensions: Record<string, unknown>;
+}
+
+const ModuleConstructor =
+  typeof module !== 'undefined' && module.constructor.length > 1
+    ? (module.constructor as unknown as ModuleConstructorWithExtensions)
+    : (BuiltinModule as unknown as ModuleConstructorWithExtensions);
+const extensionNames = Object.keys(ModuleConstructor._extensions).concat(['.cjs', '.mjs']);
+
+export class RealLoaderFS implements LoaderFS {
+  exists(filepath: string): boolean {
+    return fs.existsSync(filepath);
+  }
+
+  stat(filepath: string): Stats {
+    return fs.statSync(filepath);
+  }
+
+  realpath(filepath: string): string {
+    return fs.realpathSync(filepath);
+  }
+
+  readJSON<T = unknown>(filepath: string): T {
+    return readJSONSync(filepath) as T;
+  }
+
+  glob(patterns: string | string[], options?: LoaderFSGlobOptions): string[] {
+    return globby.sync(patterns, options);
+  }
+
+  async loadFile(filepath: string): Promise<unknown> {
+    debug('[loadFile:start] filepath: %s', filepath);
+    try {
+      const extname = path.extname(filepath);
+      if (extname && !extensionNames.includes(extname) && extname !== '.ts') {
+        return fs.readFileSync(filepath);
+      }
+      return await importModule(filepath, { importDefaultOnly: true });
+    } catch (e) {
+      if (!(e instanceof Error)) {
+        console.trace(e);
+        throw e;
+      }
+      const err = new Error(`[egg/core] load file: ${filepath}, error: ${e.message}`);
+      err.cause = e;
+      debug('[loadFile] handle %s error: %s', filepath, e);
+      throw err;
+    }
+  }
+}

packages/loader-fs/test/fixtures/loadfile/no-js.yml

@@ -0,0 +1 @@
+foo: bar

packages/loader-fs/test/fixtures/loadfile/null.js

@@ -0,0 +1,3 @@
+'use strict';
+
+module.exports = null;

packages/loader-fs/test/fixtures/loadfile/object.js

@@ -0,0 +1,3 @@
+'use strict';
+
+module.exports = { a: 1 };

packages/loader-fs/test/fixtures/loadfile/package.json

@@ -0,0 +1,3 @@
+{
+  "type": "commonjs"
+}

packages/core/test/loader/loader_fs.test.ts → packages/loader-fs/test/index.test.ts

@@ -1,17 +1,18 @@
 import assert from 'node:assert/strict';
 import fs from 'node:fs';
 import path from 'node:path';
+import { fileURLToPath } from 'node:url';
 
 import globby from 'globby';
 import { describe, it } from 'vitest';
 
-import { RealLoaderFS } from '../../src/loader/loader_fs.ts';
-import utils from '../../src/utils/index.ts';
-import { getFilepath } from '../helper.ts';
+import { RealLoaderFS } from '../src/index.ts';
 
-describe('test/loader/loader_fs.test.ts', () => {
+const __dirname = path.dirname(fileURLToPath(import.meta.url));
+
+describe('test/index.test.ts', () => {
   const loaderFS = new RealLoaderFS();
-  const baseDir = getFilepath('loadfile');
+  const baseDir = path.join(__dirname, 'fixtures/loadfile');
 
   it('should wrap exists/stat/realpath with node fs behavior', () => {
     const filepath = path.join(baseDir, 'object.js');
@@ -26,11 +27,9 @@
     const packagePath = path.join(baseDir, 'package.json');
     const patterns = ['*.js', '!null.js'];
 
-    assert.deepEqual(await loaderFS.readJSON(packagePath), JSON.parse(fs.readFileSync(packagePath, 'utf8')));
+    assert.deepEqual(loaderFS.readJSON(packagePath), JSON.parse(fs.readFileSync(packagePath, 'utf8')));
     assert.deepEqual(loaderFS.glob(patterns, { cwd: baseDir }).sort(), globby.sync(patterns, { cwd: baseDir }).sort());
-    assert.deepEqual(
-      await loaderFS.loadFile(path.join(baseDir, 'object.js')),
-      await utils.loadFile(path.join(baseDir, 'object.js')),
-    );
+    assert.deepEqual(await loaderFS.loadFile(path.join(baseDir, 'object.js')), { a: 1 });
+    assert.deepEqual(await loaderFS.loadFile(path.join(baseDir, 'no-js.yml')), Buffer.from('foo: bar\n'));
   });
 });

packages/loader-fs/tsconfig.json

@@ -0,0 +1,3 @@
+{
+  "extends": "../../tsconfig.json"
+}

packages/loader-fs/tsdown.config.ts

@@ -0,0 +1,7 @@
+import { defineConfig } from 'tsdown';
+
+export default defineConfig({
+  entry: {
+    index: 'src/index.ts',
+  },
+});

tsconfig.json

@@ -20,6 +20,9 @@
     {
       "path": "./packages/core"
     },
+    {
+      "path": "./packages/loader-fs"
+    },
     {
       "path": "./packages/errors"
     },

wiki/index.md

@@ -20,6 +20,7 @@ Read this file before exploring raw sources.
 
 - [Core Package](./packages/core.md) - Loader, lifecycle, and application core primitives used by Egg runtime packages.
 - [Egg Bundler](./packages/egg-bundler.md) - Tooling package that bundles Egg applications and backs `egg-bin bundle`.
+- [Loader FS Package](./packages/loader-fs.md) - Shared loader-facing filesystem boundary and default real filesystem implementation.
 - [Onerror Plugin](./packages/onerror.md) - Default Egg error-handling plugin and configurable response negotiation layer.
 - [Typings Package](./packages/typings.md) - Shared TypeScript type surface for cross-package Egg typings.
 - [Utils Package](./packages/utils.md) - Shared utility package for module loading and bundled module-loader integration.

wiki/log.md

@@ -2,9 +2,15 @@
 
 Dates use the workspace-local Asia/Shanghai calendar date.
 
+## [2026-05-10] package | extract LoaderFS package boundary
+
+- sources touched: `packages/loader-fs/src/index.ts`, `packages/core/src/index.ts`, `packages/core/src/loader/file_loader.ts`, `packages/core/src/loader/context_loader.ts`, `packages/core/src/loader/egg_loader.ts`
+- pages updated: `wiki/index.md`, `wiki/log.md`, `wiki/packages/core.md`, `wiki/packages/loader-fs.md`
+- note: Moved `LoaderFS` and `RealLoaderFS` into `@eggjs/loader-fs` so core, tegg, and bundled runtimes can share the loader-facing boundary without a core dependency.
+
 ## [2026-05-07] package | document core LoaderFS boundary
 
-- sources touched: `packages/core/src/index.ts`, `packages/core/src/loader/loader_fs.ts`, `packages/core/src/loader/file_loader.ts`, `packages/core/src/loader/context_loader.ts`, `packages/core/src/loader/egg_loader.ts`
+- sources touched: `packages/core/src/index.ts`, `packages/core/src/loader/file_loader.ts`, `packages/core/src/loader/context_loader.ts`, `packages/core/src/loader/egg_loader.ts`
 - pages updated: `wiki/index.md`, `wiki/log.md`, `wiki/packages/core.md`
 - note: Recorded `LoaderFS` as the minimal loader filesystem boundary and `RealLoaderFS` as the default implementation for existing non-bundled behavior.
 

wiki/packages/core.md

@@ -4,7 +4,6 @@ type: package
 summary: Loader, lifecycle, and application core primitives used by Egg runtime packages.
 source_files:
   - packages/core/src/index.ts
-  - packages/core/src/loader/loader_fs.ts
   - packages/core/src/loader/file_loader.ts
   - packages/core/src/loader/context_loader.ts
   - packages/core/src/loader/egg_loader.ts
@@ -20,14 +19,11 @@ support, lifecycle, and base context classes.
 
 ## LoaderFS
 
-`LoaderFS` is the minimal filesystem boundary for loader-facing file access. It
-covers `exists`, `stat`, `realpath`, `readJSON`, `glob`, and `loadFile` without
-trying to polyfill the full Node.js `fs` module.
-
-`RealLoaderFS` is the default implementation. It preserves normal non-bundled
-runtime behavior by delegating to `fs.existsSync`, `fs.statSync`,
-`fs.realpathSync`, `utility.readJSONSync`, `globby.sync`, and the existing
-`utils.loadFile()` helper.
+`@eggjs/core` depends on `@eggjs/loader-fs` for the minimal loader-facing
+filesystem boundary. It re-exports `LoaderFS`, `LoaderFSGlobOptions`, and
+`RealLoaderFS` for core loader consumers, but the implementation lives in the
+standalone package so tegg and bundled runtimes can share the same small
+boundary without depending on core.
 
 `EggLoaderOptions`, `FileLoaderOptions`, and `ContextLoaderOptions` can carry a
 custom `loaderFS`. `EggLoader` passes its loader FS into `loadToApp()` and

wiki/packages/loader-fs.md

@@ -0,0 +1,27 @@
+---
+title: Loader FS Package
+type: package
+summary: Shared loader-facing filesystem boundary and default real filesystem implementation.
+source_files:
+  - packages/loader-fs/src/index.ts
+  - packages/loader-fs/test/index.test.ts
+updated_at: 2026-05-10
+status: active
+---
+
+# Loader FS Package
+
+`@eggjs/loader-fs` owns the small filesystem boundary shared by Egg loader
+runtimes. It is not a full Node.js `fs` polyfill; it only covers the loader
+operations needed by Egg-style file discovery and loading: `exists`, `stat`,
+`realpath`, `readJSON`, `glob`, and `loadFile`.
+
+`RealLoaderFS` is the default implementation. It preserves normal non-bundled
+runtime behavior by delegating to `fs.existsSync`, `fs.statSync`,
+`fs.realpathSync`, `utility.readJSONSync`, `globby.sync`, and Egg's standard
+module loading semantics through `@eggjs/utils` `importModule()`.
+
+`@eggjs/core` consumes and re-exports this package for `EggLoader`,
+`FileLoader`, and `ContextLoader` options. Future manifest-backed or bundled
+loaders can provide another `LoaderFS` implementation without making tegg or
+runtime packages depend on `@eggjs/core`.