Add fs-extra/esm ESM named import module, with just fs-extra methods

Fixes #746

README.md

@@ -27,6 +27,8 @@ Installation
 Usage
 -----
 
+### CommonJS
+
 `fs-extra` is a drop in replacement for native `fs`. All methods in `fs` are attached to `fs-extra`. All `fs` methods return promises if the callback isn't passed.
 
 You don't ever need to include the original `fs` module again:
@@ -55,6 +57,31 @@ const fs = require('fs')
 const fse = require('fs-extra')
 ```
 
+### ESM
+
+There is also an `fs-extra/esm` import, that supports both default and named exports. However, note that `fs` methods are not included in `fs-extra/esm`; you still need to import `fs` and/or `fs/promises` seperately:
+
+```js
+import { readFileSync } from 'fs'
+import { readFile } from 'fs/promises'
+import { outputFile, outputFileSync } from 'fs-extra/esm'
+```
+
+Default exports are supported:
+
+```js
+import fs from 'fs'
+import fse from 'fs-extra/esm'
+// fse.readFileSync is not a function; must use fs.readFileSync
+```
+
+but you probably want to just use regular `fs-extra` instead of `fs-extra/esm` for default exports:
+
+```js
+import fs from 'fs-extra'
+// both fs and fs-extra methods are defined
+```
+
 Sync vs Async vs Async/Await
 -------------
 Most methods are async by default. All async methods will return a promise if the callback isn't passed.
@@ -197,7 +224,8 @@ fs-extra contains hundreds of tests.
 
 - `npm run lint`: runs the linter ([standard](http://standardjs.com/))
 - `npm run unit`: runs the unit tests
-- `npm test`: runs both the linter and the tests
+- `npm run unit-esm`: runs tests for `fs-extra/esm` exports
+- `npm test`: runs the linter and all tests
 
 
 ### Windows

lib/esm.mjs

@@ -0,0 +1,68 @@
+import _copy from './copy/index.js'
+import _empty from './empty/index.js'
+import _ensure from './ensure/index.js'
+import _json from './json/index.js'
+import _mkdirs from './mkdirs/index.js'
+import _move from './move/index.js'
+import _outputFile from './output-file/index.js'
+import _pathExists from './path-exists/index.js'
+import _remove from './remove/index.js'
+
+// NOTE: Only exports fs-extra's functions; fs functions must be imported from "node:fs" or "node:fs/promises"
+
+export const copy = _copy.copy
+export const copySync = _copy.copySync
+export const emptyDirSync = _empty.emptyDirSync
+export const emptydirSync = _empty.emptydirSync
+export const emptyDir = _empty.emptyDir
+export const emptydir = _empty.emptydir
+export const createFile = _ensure.createFile
+export const createFileSync = _ensure.createFileSync
+export const ensureFile = _ensure.ensureFile
+export const ensureFileSync = _ensure.ensureFileSync
+export const createLink = _ensure.createLink
+export const createLinkSync = _ensure.createLinkSync
+export const ensureLink = _ensure.ensureLink
+export const ensureLinkSync = _ensure.ensureLinkSync
+export const createSymlink = _ensure.createSymlink
+export const createSymlinkSync = _ensure.createSymlinkSync
+export const ensureSymlink = _ensure.ensureSymlink
+export const ensureSymlinkSync = _ensure.ensureSymlinkSync
+export const readJson = _json.readJson
+export const readJSON = _json.readJSON
+export const readJsonSync = _json.readJsonSync
+export const readJSONSync = _json.readJSONSync
+export const writeJson = _json.writeJson
+export const writeJSON = _json.writeJSON
+export const writeJsonSync = _json.writeJsonSync
+export const writeJSONSync = _json.writeJSONSync
+export const outputJson = _json.outputJson
+export const outputJSON = _json.outputJSON
+export const outputJsonSync = _json.outputJsonSync
+export const outputJSONSync = _json.outputJSONSync
+export const mkdirs = _mkdirs.mkdirs
+export const mkdirsSync = _mkdirs.mkdirsSync
+export const mkdirp = _mkdirs.mkdirp
+export const mkdirpSync = _mkdirs.mkdirpSync
+export const ensureDir = _mkdirs.ensureDir
+export const ensureDirSync = _mkdirs.ensureDirSync
+export const move = _move.move
+export const moveSync = _move.moveSync
+export const outputFile = _outputFile.outputFile
+export const outputFileSync = _outputFile.outputFileSync
+export const pathExists = _pathExists.pathExists
+export const pathExistsSync = _pathExists.pathExistsSync
+export const remove = _remove.remove
+export const removeSync = _remove.removeSync
+
+export default {
+  ..._copy,
+  ..._empty,
+  ..._ensure,
+  ..._json,
+  ..._mkdirs,
+  ..._move,
+  ..._outputFile,
+  ..._pathExists,
+  ..._remove
+}

package.json

@@ -51,16 +51,20 @@
     "read-dir-files": "^0.1.1",
     "standard": "^16.0.3"
   },
-  "exports": "./lib/index.js",
+  "exports": {
+    ".": "./lib/index.js",
+    "./esm": "./lib/esm.mjs"
+  },
   "files": [
     "lib/",
     "!lib/**/__tests__/"
   ],
   "scripts": {
     "lint": "standard",
     "test-find": "find ./lib/**/__tests__ -name *.test.js | xargs mocha",
-    "test": "npm run lint && npm run unit",
-    "unit": "nyc node test.js"
+    "test": "npm run lint && npm run unit && npm run unit-esm",
+    "unit": "nyc node test.js",
+    "unit-esm": "node test.mjs"
   },
   "sideEffects": false
 }

test.mjs

@@ -0,0 +1,116 @@
+import assert from 'assert'
+import fsLegacy from './lib/index.js'
+// NOTE: eslint comments needed because we're importing the same file multiple times
+import fsDefault from './lib/esm.mjs' // eslint-disable-line
+import * as fsStar from './lib/esm.mjs'
+import {
+  copy,
+  copySync,
+  emptyDirSync,
+  emptydirSync,
+  emptyDir,
+  emptydir,
+  createFile,
+  createFileSync,
+  ensureFile,
+  ensureFileSync,
+  createLink,
+  createLinkSync,
+  ensureLink,
+  ensureLinkSync,
+  createSymlink,
+  createSymlinkSync,
+  ensureSymlink,
+  ensureSymlinkSync,
+  readJson,
+  readJsonSync,
+  writeJson,
+  writeJsonSync,
+  outputJson,
+  outputJsonSync,
+  outputJSON,
+  outputJSONSync,
+  writeJSON,
+  writeJSONSync,
+  readJSON,
+  readJSONSync,
+  mkdirs,
+  mkdirsSync,
+  mkdirp,
+  mkdirpSync,
+  ensureDir,
+  ensureDirSync,
+  move,
+  moveSync,
+  outputFile,
+  outputFileSync,
+  pathExists,
+  pathExistsSync,
+  remove,
+  removeSync
+} from './lib/esm.mjs' // eslint-disable-line
+const fsNamed = [
+  copy,
+  copySync,
+  emptyDirSync,
+  emptydirSync,
+  emptyDir,
+  emptydir,
+  createFile,
+  createFileSync,
+  ensureFile,
+  ensureFileSync,
+  createLink,
+  createLinkSync,
+  ensureLink,
+  ensureLinkSync,
+  createSymlink,
+  createSymlinkSync,
+  ensureSymlink,
+  ensureSymlinkSync,
+  readJson,
+  readJsonSync,
+  writeJson,
+  writeJsonSync,
+  outputJson,
+  outputJsonSync,
+  outputJSON,
+  outputJSONSync,
+  writeJSON,
+  writeJSONSync,
+  readJSON,
+  readJSONSync,
+  mkdirs,
+  mkdirsSync,
+  mkdirp,
+  mkdirpSync,
+  ensureDir,
+  ensureDirSync,
+  move,
+  moveSync,
+  outputFile,
+  outputFileSync,
+  pathExists,
+  pathExistsSync,
+  remove,
+  removeSync
+]
+
+const keys = Object.keys(fsDefault)
+
+assert.deepStrictEqual(Object.values(fsDefault), fsNamed, 'named and default exports should match')
+assert.deepStrictEqual(
+  Object.entries(fsStar)
+    .filter(([name]) => name !== 'default') // remove "default" property here
+    .sort(([nameA], [nameB]) => keys.indexOf(nameA) - keys.indexOf(nameB)) // sort for exact match
+    .map(([name, fn]) => fn),
+  Object.values(fsDefault),
+  'star and default exports should match'
+)
+
+// default exports a subset of the legacy implementation, but functions are the same
+Object.entries(fsDefault).forEach(([name, fn]) => {
+  assert.strictEqual(fn, fsLegacy[name], `${name}() should match legacy implementation`)
+})
+
+console.warn('ESM tests pass!')