package-exports

Get the exports of a package.

Contents

• What is this?
• When should I use this?
• Install
• Use
• API
  • packageExports(folder)
  • Export
  • Result
• Errors
  • exports-alternatives
  • exports-alternatives-empty
  • exports-conditions-default-misplaced
  • exports-conditions-default-missing
  • exports-conditions-mutually-exclusive
  • exports-conditions-verbose
  • exports-main-missing
  • exports-negated-missing
  • exports-object-empty
  • exports-object-mixed
  • exports-path-not-found
  • exports-path-unprefixed
  • exports-path-wildcard-not-found
  • exports-specifier-extension
  • exports-specifier-nested
  • exports-specifier-wildcard-invalid
  • exports-specifier-wildcard-useless
  • exports-specifiers-verbose
  • exports-types-verbose
  • exports-value-invalid
  • files-missing
  • main
  • main-extra
  • main-inferred
  • main-invalid
  • main-missing
  • main-not-found
  • main-resolve-commonjs
  • main-resolve-module
  • name-missing
  • npm-ignored
  • type-invalid
  • type-missing
• Compatibility
• Security
• Contribute
• License

What is this?

This package find out what is exposed from a package. It also emits many possible warnings about potential problems.

When should I use this?

You can use this to programatically figure out what can be used from a package. You can also use this to lint packages.

Install

This package is ESM only. In Node.js (version 18+), install with npm:

npm install package-exports

Use

import {packageExports} from 'package-exports'
import {reporter} from 'vfile-reporter'

const thisPackage = await packageExports(new URL('.', import.meta.url))

console.dir(thisPackage, {depth: undefined})

const tar = await packageExports(new URL('node_modules/tar/', import.meta.url))
console.error(reporter(tar.file))

Yields:

{
  exports: [
    {
      conditions: undefined,
      exists: true,
      jsonPath: [ 'exports' ],
      specifier: '.',
      url: 'file:///Users/…/package-exports/index.js'
    }
  ],
  file: VFile { … },
  name: 'package-exports'
}

node_modules/tar/package.json
1:1-70:2 warning Unexpected inferred main export `./index.js`, it’s recommended to use an export map such as `"exports": "./index.js"` main-inferred package-exports
1:1-70:2 warning Unexpected missing `type` field, expected `type: 'commonjs'` or `'module'`                                            type-missing  package-exports

⚠ 2 warnings

API

This package exports the identifier packageExports. It exports the TypeScript types Export and Result. There is no default export.

packageExports(folder)

Get the exports of a package.

Parameters

• folder (URL, required) — file URL to folder of a package

Returns

Result (Promise<Result>).

Export

Export (TypeScript type).

Fields

• conditions (Array<string>) — conditions
• exists (boolean) — whether this file exists
• jsonPath (Array<number | string>) — path in package.json
• specifier (string) — specifier that exposes this
• url (URL) — resolved URL to file

Result

Result of finding exports (TypeScript type).

Fields

• exports (Array<Exports>) — exports
• file (VFile) – file
• name (string or undefined) – package name

Errors

This package lints for many problems in npm packages and adds each message to the vfile. Messages will have a source field set to package-exports and a ruleId to one of the following values.

exports-alternatives

package.json:

{
  "exports": {
    ".": "./index.js",
    "./other": [
      "./other.js"
    ]
  },
  "files": [
    "index.js",
    "other.js"
  ],
  "name": "x",
  "type": "module"
}

Yields:

4:16-6:6: Unexpected alternatives list at `exports['./other']`, several tools don’t support this and pick the first item

Fix:

@@ -1,7 +1,7 @@
 {
   "exports": {
     ".": "./index.js",
-    "./other": ["./other.js"]
+    "./other": "./other.js"
   },
   "files": ["index.js", "other.js"],
   "name": "x",

exports-alternatives-empty

package.json:

{
  "exports": {
    ".": "./index.js",
    "./other": []
  },
  "files": [
    "index.js"
  ],
  "name": "x",
  "type": "module"
}

Yields:

4:16-4:18: Unexpected empty array at `exports['./other']` doing nothing, expected a single item

Fix:

@@ -1,7 +1,6 @@
 {
   "exports": {
-    ".": "./index.js",
-    "./other": []
+    ".": "./index.js"
   },
   "files": ["index.js"],
   "name": "x",

exports-conditions-default-misplaced

package.json:

{
  "exports": {
    "default": "./index.js",
    "production": "./other.js"
  },
  "files": [
    "index.js",
    "other.js"
  ],
  "name": "x",
  "type": "module"
}

Yields:

4:19-4:31: Unexpected non-last `default` conditions at `exports` ignoring everything after it, move the `default` condition to the end

Fix:

@@ -1,7 +1,7 @@
 {
   "exports": {
-    "default": "./index.js",
-    "production": "./other.js"
+    "production": "./other.js",
+    "default": "./index.js"
   },
   "files": ["index.js", "other.js"],
   "name": "x",

exports-conditions-default-missing

package.json:

{
  "exports": {
    "production": "./index.js"
  },
  "files": [
    "index.js"
  ],
  "name": "x",
  "type": "module"
}

Yields:

2:14-4:4: Unexpected conditions without a `default` entry at `exports` making specifier `.` unusable by default, expected `'default'` condition as the last field

Fix:

@@ -1,6 +1,7 @@
 {
   "exports": {
-    "production": "./index.js"
+    "production": "./index.js",
+    "default": "./other.js"
   },
   "files": [
     "index.js"

exports-conditions-mutually-exclusive

package.json:

{
  "exports": {
    "import": {
      "require": "./other.js",
      "default": "./index.js"
    },
    "default": "./index.js"
  },
  "files": [
    "index.js",
    "other.js"
  ],
  "name": "x",
  "type": "module"
}

Yields:

4:18-4:30: Unexpected condition `require` mutually exclusive with `import` at `exports.import` which never matches, use only one of these conditions

Fix:

@@ -1,10 +1,7 @@
 {
   "exports": {
-    "import": {
-      "require": "./other.js",
-      "default": "./index.js"
-    },
-    "default": "./index.js"
+    "require": "./other.js",
+    "import": "./index.js"
   },
   "files": [
     "index.js",

exports-conditions-verbose

package.json:

{
  "exports": {
    "default": "./index.js"
  },
  "files": [
    "index.js"
  ],
  "name": "x",
  "type": "module"
}

Yields:

2:14-4:4: Unexpected verbose conditions object with sole key `default` at `exports`, replace the object with the value at `default`

Fix:

@@ -1,7 +1,5 @@
 {
-  "exports": {
-    "default": "./index.js"
-  },
+  "exports": "./index.js",
   "files": [
     "index.js"
   ],

exports-main-missing

package.json:

{
  "exports": {
    "./x": "./index.js"
  },
  "files": [
    "index.js"
  ],
  "name": "x",
  "type": "module"
}

Yields:

1:1-10:2: Unexpected missing main specifier `.`, expected an export to the main module

Fix:

@@ -1,5 +1,6 @@
 {
   "exports": {
+    ".": "./index.js",
     "./x": "./index.js"
   },
   "files": [

exports-negated-missing

package.json:

{
  "exports": {
    ".": "./index.js",
    "./*": null
  },
  "files": [
    "index.js"
  ],
  "name": "x",
  "type": "module"
}

Yields:

4:12-4:16: Unexpected negation specifier `./*` at `exports['./*']` with nothing to negate

Fix:

@@ -1,6 +1,7 @@
 {
   "exports": {
     ".": "./index.js",
+    "./x": "./index.js",
     "./*": null
   },
   "files": [

exports-object-empty

package.json:

{
  "exports": {
    ".": "./index.js",
    "./other": {}
  },
  "files": [
    "index.js"
  ],
  "name": "x",
  "type": "module"
}

Yields:

4:16-4:18: Unexpected empty object at `exports['./other']` doing nothing, expected fields

Fix:

@@ -1,7 +1,6 @@
 {
   "exports": {
-    ".": "./index.js",
-    "./other": {}
+    ".": "./index.js"
   },
   "files": [
     "index.js"

exports-object-mixed

package.json:

{
  "exports": {
    ".": "./index.js",
    "default": "./other.js"
  },
  "files": [
    "index.js",
    "other.js"
  ],
  "name": "x",
  "type": "module"
}

Yields:

1:1-12:2: Unexpected missing main specifier `.`, expected an export to the main module
2:14-5:4: Unexpected mixed specifiers (starting with `.`) and conditions (without `.`) at `exports`, expected either specifiers or conditions

Fix:

@@ -1,6 +1,6 @@
 {
   "exports": {
-    ".": "./index.js",
+    "other": "./index.js",
     "default": "./other.js"
   },
   "files": [

exports-path-not-found

package.json:

{
  "exports": {
    ".": "./index.js",
    "./x": "./missing.js"
  },
  "files": [
    "index.js",
    "missing.js"
  ],
  "name": "x",
  "type": "module"
}

Yields:

4:12-4:26: Unexpected missing file `./missing.js` for specifier `./x` at `exports['./x']`

Fix: make sure files exist.

exports-path-unprefixed

package.json:

{
  "exports": "index.js",
  "files": [
    "index.js"
  ],
  "name": "x",
  "type": "module"
}

Yields:

1:1-8:2: Unexpected missing main specifier `.`, expected an export to the main module
2:14-2:24: Unexpected unprefixed value `'index.js'` at `exports` which is not importable, did you mean `'./index.js'`

Fix:

@@ -1,5 +1,5 @@
 {
-  "exports": "index.js",
+  "exports": "./index.js",
   "files": [
     "index.js"
   ],

exports-path-wildcard-not-found

package.json:

{
  "exports": {
    ".": "./index.js",
    "./*": "./lib/*"
  },
  "files": [
    "lib/",
    "index.js"
  ],
  "name": "x",
  "type": "module"
}

Yields:

4:12-4:21: Unexpected dynamic file glob `./lib/*` at `exports['./*']` pointing to nothing, expected files

Fix: make sure files exist.

exports-specifier-extension

package.json:

{
  "exports": {
    ".": "./index.js",
    "./other.js": "./other.js"
  },
  "files": [
    "index.js",
    "other.js"
  ],
  "name": "x",
  "type": "module"
}

Yields:

2:14-5:4: Unexpected extension `.js` in specifier `./other.js` at `exports`, extensions have no meaning in specifiers, expected `./other`

Fix:

@@ -1,7 +1,7 @@
 {
   "exports": {
     ".": "./index.js",
-    "./other.js": "./other.js"
+    "./other": "./other.js"
   },
   "files": [
     "index.js",

exports-specifier-nested

package.json:

{
  "exports": {
    ".": "./index.js",
    "./other": {
      "./more": "./other.js"
    }
  },
  "files": [
    "index.js",
    "other.js"
  ],
  "name": "x",
  "type": "module"
}

Yields:

4:16-6:6: Unexpected nested specifier `./more` at `exports['./other']`, expected conditions

Fix:

@@ -1,9 +1,7 @@
 {
   "exports": {
     ".": "./index.js",
-    "./other": {
-      "./more": "./other.js"
-    }
+    "./other/more": "./other.js"
   },
   "files": [
     "index.js",

exports-specifier-wildcard-invalid

package.json:

{
  "exports": {
    ".": "./index.js",
    "./x/*/y/*": "./other.js"
  },
  "files": [
    "index.js",
    "other.js"
  ],
  "name": "x",
  "type": "module"
}

Yields:

4:18-4:30: Unexpected extra wildcard in dynamic specifier `./x/*/y/*` at `exports['./x/*/y/*']`, one wildcard is allowed

Fix:

@@ -1,7 +1,7 @@
 {
   "exports": {
     ".": "./index.js",
-    "./x/*/y/*": "./other.js"
+    "./x/*/y": "./other.js"
   },
   "files": [
     "index.js",

exports-specifier-wildcard-useless

package.json:

{
  "exports": {
    ".": "./index.js",
    "./*": "./other.js"
  },
  "files": [
    "index.js",
    "other.js"
  ],
  "name": "x",
  "type": "module"
}

Yields:

4:12-4:24: Unexpected dynamic specifier `./*` pointing to static file `./other.js` at `exports['./*']`, use dynamic specifiers with dynamic file globs

Fix:

@@ -1,7 +1,7 @@
 {
   "exports": {
     ".": "./index.js",
-    "./*": "./other.js"
+    "./other": "./other.js"
   },
   "files": [
     "index.js",

exports-specifiers-verbose

package.json:

{
  "exports": {
    ".": "./index.js"
  },
  "files": [
    "index.js"
  ],
  "name": "x",
  "type": "module"
}

Yields:

2:14-4:4: Unexpected verbose specifier object with sole key `.` at `exports`, replace the object with the value at `.`

Fix:

@@ -1,7 +1,5 @@
 {
-  "exports": {
-    ".": "./index.js"
-  },
+  "exports": "./index.js",
   "files": [
     "index.js"
   ],

exports-types-verbose

package.json:

{
  "exports": {
    "types": "./index.d.ts",
    "default": "./index.js"
  },
  "files": [
    "index.d.ts",
    "index.js"
  ],
  "name": "x",
  "type": "module"
}

Yields:

3:14-3:28: Unexpected verbose `types` condition at `exports` matching what TypeScript would load for `default` without it, remove it

Fix:

@@ -1,8 +1,5 @@
 {
-  "exports": {
-    "types": "./index.d.ts",
-    "default": "./index.js"
-  },
+  "exports": "./index.js",
   "files": [
     "index.d.ts",
     "index.js"

exports-value-invalid

package.json:

{
  "exports": {
    ".": "./index.js",
    "./other": 1
  },
  "files": [
    "index.js"
  ],
  "name": "x",
  "type": "module"
}

Yields:

4:16-4:17: Unexpected invalid value `1` at `exports['./other']` which is not importable, expected conditions object, `string` (path to file), or `null` (negated)

Fix:

+++ b/example/package.json
@@ -1,7 +1,7 @@
 {
   "exports": {
     ".": "./index.js",
-    "./other": 1
+    "./other": "./other.js"
   },
   "files": [
     "index.js"

files-missing

package.json:

{
  "exports": "./index.js",
  "name": "x",
  "type": "module",
}

Yields:

1:1-5:2: Unexpected missing `files` field, expected array of allowed files to include

Fix:

@@ -1,5 +1,8 @@
 {
   "exports": "./index.js",
+  "files": [
+    "index.js"
+  ],
   "name": "x",
   "type": "module"
 }

main

package.json:

{
  "files": [
    "index.js",
    "other.js"
  ],
  "main": "index.js",
  "name": "x",
  "type": "module"
}

Yields:

6:11-6:21: Unexpected legacy `main` field that does not encapsulate the package, it’s recommended to use an export map such as `"exports": "./index.js"`

Fix:

@@ -1,9 +1,9 @@
 {
+  "exports": "./index.js",
   "files": [
     "index.js",
     "other.js"
   ],
-  "main": "index.js",
   "name": "x",
   "type": "module"
 }

main-extra

package.json:

{
  "exports": "./index.js",
  "files": [
    "index.js"
  ],
  "main": "index.js",
  "name": "x",
  "type": "module"
}

Yields:

6:11-6:21: Unexpected unused legacy `main` field with modern `exports`, remove it

Fix:

@@ -3,7 +3,6 @@
   "files": [
     "index.js"
   ],
-  "main": "index.js",
   "name": "x",
   "type": "module"
 }

main-inferred

package.json:

{
  "files": [
    "index.js"
  ],
  "name": "x",
  "type": "commonjs"
}

Yields:

1:1-7:2: Unexpected inferred main export `./index.js`, it’s recommended to use an export map such as `"exports": "./index.js"`

Fix:

@@ -1,4 +1,5 @@
 {
+  "exports": "./index.js",
   "files": [
     "index.js"
   ],

main-invalid

package.json:

{
  "files": [
    "index.js"
  ],
  "main": 1,
  "name": "x",
  "type": "commonjs"
}

Yields:

1:1-8:2: Unexpected inferred main export `./index.js`, it’s recommended to use an export map such as `"exports": "./index.js"`
5:11-5:12: Unexpected non-string `main` field `1`

Fix:

@@ -1,8 +1,8 @@
 {
+  "exports": "./index.js",
   "files": [
     "index.js"
   ],
-  "main": 1,
   "name": "x",
   "type": "commonjs"
 }

main-missing

package.json:

{
  "files": [
    "default.js"
  ],
  "name": "x",
  "type": "commonjs"
}

Yields:

1:1-7:2: Unexpected missing main module, it’s recommended to use an export map such as `"exports": "./index.js"`

Fix:

@@ -1,4 +1,5 @@
 {
+  "exports": "./default.js",
   "files": [
     "default.js"
   ],

main-not-found

package.json:

{
  "files": [
    "index.js"
  ],
  "main": "./missing.js",
  "name": "x",
  "type": "commonjs"
}

Yields:

1:1-8:2: Unexpected inferred main export `./index.js`, it’s recommended to use an export map such as `"exports": "./index.js"`
5:11-5:25: Unexpected missing file for `main` field `./missing.js`

Fix:

@@ -1,8 +1,8 @@
 {
+  "exports": "./index.js",
   "files": [
     "index.js"
   ],
-  "main": "./missing.js",
   "name": "x",
   "type": "commonjs"
 }

main-resolve-commonjs

package.json:

{
  "files": [
    "index.js"
  ],
  "main": "index",
  "name": "x",
  "type": "commonjs"
}

Yields:

5:11-5:18: Unexpected `main` field `index` that resolves to `./index.js` in CJS, this works but is slow and doesn’t work with `type: 'module', use the resolved value explicitly

Fix:

@@ -1,8 +1,8 @@
 {
+  "exports": "./index.js",
   "files": [
     "index.js"
   ],
-  "main": "index",
   "name": "x",
   "type": "commonjs"
 }

main-resolve-module

package.json:

{
  "files": [
    "index.js"
  ],
  "main": "index",
  "name": "x",
  "type": "module"
}

Yields:

1:1-9:2: Unexpected inferred main export `./index.js`, it’s recommended to use an export map such as `"exports": "./index.js"`
6:11-6:18: Unexpected `main` field `index` that does not resolve with `type: 'module'`, use an export map such as `"exports": "./index.js"`

Fix:

@@ -1,8 +1,8 @@
 {
+  "exports": "./index.js",
   "files": [
     "index.js"
   ],
-  "main": "index",
   "name": "x",
   "type": "module"
 }

name-missing

package.json:

{
  "exports": "./index.js",
  "files": [
    "index.js"
  ],
  "type": "module"
}

Yields:

1:1-7:2: Unexpected missing `name` field, expected a package name

Fix:

@@ -3,5 +3,6 @@
   "files": [
     "index.js"
   ],
+  "name": "x",
   "type": "module"
 }

npm-ignored

package.json:

{
  "exports": {
    ".": "./index.js",
    "./other": "./other.js"
  },
  "files": [
    "index.js"
  ],
  "name": "x",
  "type": "module"
}

Yields:

4:16-4:28: Unexpected file `./other.js` at `exports['./other']` which is excluded from the npm package, add it to `files` in `package.json`

Fix:

@@ -4,7 +4,8 @@
     "./other": "./other.js"
   },
   "files": [
-    "index.js"
+    "index.js",
+    "other.js"
   ],
   "name": "x",
   "type": "module"

type-invalid

package.json:

{
  "exports": "./index.js",
  "files": [
    "index.js"
  ],
  "name": "x",
  "type": "umd",
}

Yields:

7:11-7:16: Unexpected invalid `type` value `umd`, expected `commonjs` or `module`

Fix:

@@ -4,5 +4,5 @@
     "index.js"
   ],
   "name": "x",
-  "type": "umd"
+  "type": "module"
 }

type-missing

package.json:

{
  "exports": "./index.js",
  "files": [
    "index.js"
  ],
  "name": "x"
}

Yields:

1:1-7:2: Unexpected missing `type` field, expected `type: 'commonjs'` or `'module'`

Fix:

@@ -3,5 +3,6 @@
   "files": [
     "index.js"
   ],
-  "name": "x"
+  "name": "x",
+  "type": "commonjs"
 }

Compatibility

This projects is compatible with maintained versions of Node.js.

When we cut a new major release, we drop support for unmaintained versions of Node. This means we try to keep the current release line, package-exports@1, compatible with Node.js 18.

Security

This package is safe.

Contribute

Yes please! See How to Contribute to Open Source.

License

MIT © Titus Wormer