npm package discovery and stats viewer.

Discover Tips

  • General search

    [free text search, go nuts!]

  • Package details

    pkg:[package-name]

  • User packages

    @[username]

Sponsor

Optimize Toolset

I’ve always been into building performant and accessible sites, but lately I’ve been taking it extremely seriously. So much so that I’ve been building a tool to help me optimize and monitor the sites that I build to make sure that I’m making an attempt to offer the best experience to those who visit them. If you’re into performant, accessible and SEO friendly sites, you might like it too! You can check it out at Optimize Toolset.

About

Hi, 👋, I’m Ryan Hefner  and I built this site for me, and you! The goal of this site was to provide an easy way for me to check the stats on my npm packages, both for prioritizing issues and updates, and to give me a little kick in the pants to keep up on stuff.

As I was building it, I realized that I was actually using the tool to build the tool, and figured I might as well put this out there and hopefully others will find it to be a fast and useful way to search and browse npm packages as I have.

If you’re interested in other things I’m working on, follow me on Twitter or check out the open source projects I’ve been publishing on GitHub.

I am also working on a Twitter bot for this site to tweet the most popular, newest, random packages from npm. Please follow that account now and it will start sending out packages soon–ish.

Open Software & Tools

This site wouldn’t be possible without the immense generosity and tireless efforts from the people who make contributions to the world and share their work via open source initiatives. Thank you 🙏

© 2024 – Pkg Stats / Ryan Hefner

resolve.exports

v2.0.2

Published

A tiny (952b), correct, general-purpose, and configurable "exports" and "imports" resolver without file-system reliance

Downloads

89,274,974

Readme

resolve.exports CI codecov

A tiny (952b), correct, general-purpose, and configurable "exports" and "imports" resolver without file-system reliance

Why?

Hopefully, this module may serve as a reference point (and/or be used directly) so that the varying tools and bundlers within the ecosystem can share a common approach with one another as well as with the native Node.js implementation.

With the push for ESM, we must be very careful and avoid fragmentation. If we, as a community, begin propagating different dialects of the resolution algorithm, then we're headed for deep trouble. It will make supporting (and using) "exports" nearly impossible, which may force its abandonment and along with it, its benefits.

Let's have nice things.

Install

$ npm install resolve.exports

Usage

Please see /test/ for examples.

import * as resolve from 'resolve.exports';

// package.json contents
const pkg = {
  "name": "foobar",
  "module": "dist/module.mjs",
  "main": "dist/require.js",
  "imports": {
    "#hash": {
      "import": {
        "browser": "./hash/web.mjs",
        "node": "./hash/node.mjs",
      },
      "default": "./hash/detect.js"
    }
  },
  "exports": {
    ".": {
      "import": "./dist/module.mjs",
      "require": "./dist/require.js"
    },
    "./lite": {
      "worker": {
        "browser": "./lite/worker.browser.js",
        "node": "./lite/worker.node.js"
      },
      "import": "./lite/module.mjs",
      "require": "./lite/require.js"
    }
  }
};

// ---
// Exports
// ---

// entry: "foobar" === "." === default
// conditions: ["default", "import", "node"]
resolve.exports(pkg);
resolve.exports(pkg, '.');
resolve.exports(pkg, 'foobar');
//=> ["./dist/module.mjs"]

// entry: "foobar/lite" === "./lite"
// conditions: ["default", "import", "node"]
resolve.exports(pkg, 'foobar/lite');
resolve.exports(pkg, './lite');
//=> ["./lite/module.mjs"]

// Enable `require` condition
// conditions: ["default", "require", "node"]
resolve.exports(pkg, 'foobar', { require: true }); //=> ["./dist/require.js"]
resolve.exports(pkg, './lite', { require: true }); //=> ["./lite/require.js"]

// Throws "Missing <entry> specifier in <name> package" Error
resolve.exports(pkg, 'foobar/hello');
resolve.exports(pkg, './hello/world');

// Add custom condition(s)
// conditions: ["default", "worker", "import", "node"]
resolve.exports(pkg, 'foobar/lite', {
  conditions: ['worker']
}); //=> ["./lite/worker.node.js"]

// Toggle "browser" condition
// conditions: ["default", "worker", "import", "browser"]
resolve.exports(pkg, 'foobar/lite', {
  conditions: ['worker'],
  browser: true
}); //=> ["./lite/worker.browser.js"]

// Disable non-"default" condition activate
// NOTE: breaks from Node.js default behavior
// conditions: ["default", "custom"]
resolve.exports(pkg, 'foobar/lite', {
  conditions: ['custom'],
  unsafe: true,
});
//=> Error: No known conditions for "./lite" specifier in "foobar" package

// ---
// Imports
// ---

// conditions: ["default", "import", "node"]
resolve.imports(pkg, '#hash');
resolve.imports(pkg, 'foobar/#hash');
//=> ["./hash/node.mjs"]

// conditions: ["default", "import", "browser"]
resolve.imports(pkg, '#hash', { browser: true });
resolve.imports(pkg, 'foobar/#hash');
//=> ["./hash/web.mjs"]

// conditions: ["default"]
resolve.imports(pkg, '#hash', { unsafe: true });
resolve.imports(pkg, 'foobar/#hash');
//=> ["./hash/detect.mjs"]

resolve.imports(pkg, '#hello/world');
resolve.imports(pkg, 'foobar/#hello/world');
//=> Error: Missing "#hello/world" specifier in "foobar" package

// ---
// Legacy
// ---

// prefer "module" > "main" (default)
resolve.legacy(pkg); //=> "dist/module.mjs"

// customize fields order
resolve.legacy(pkg, {
  fields: ['main', 'module']
}); //=> "dist/require.js"

API

The resolve(), exports(), and imports() functions share similar API signatures:

export function resolve(pkg: Package, entry?: string, options?: Options): string[] | undefined;
export function exports(pkg: Package, entry?: string, options?: Options): string[] | undefined;
export function imports(pkg: Package, target: string, options?: Options): string[] | undefined;
//                                         ^ not optional!

All three:

  • accept a package.json file's contents as a JSON object
  • accept a target/entry identifier
  • may accept an Options object
  • return string[], string, or undefined

The only difference is that imports() must accept a target identifier as there can be no inferred default.

See below for further API descriptions.

Note: There is also a Legacy Resolver API


resolve(pkg, entry?, options?)

Returns: string[] or undefined

A convenience helper which automatically reroutes to exports() or imports() depending on the entry value.

When unspecified, entry defaults to the "." identifier, which means that exports() will be invoked.

import * as r from 'resolve.exports';

let pkg = {
  name: 'foobar',
  // ...
};

r.resolve(pkg);
//~> r.exports(pkg, '.');

r.resolve(pkg, 'foobar');
//~> r.exports(pkg, '.');

r.resolve(pkg, 'foobar/subpath');
//~> r.exports(pkg, './subpath');

r.resolve(pkg, '#hash/md5');
//~> r.imports(pkg, '#hash/md5');

r.resolve(pkg, 'foobar/#hash/md5');
//~> r.imports(pkg, '#hash/md5');

exports(pkg, entry?, options?)

Returns: string[] or undefined

Traverse the "exports" within the contents of a package.json file. If the contents does not contain an "exports" map, then undefined will be returned.

Successful resolutions will always result in a string or string[] value. This will be the value of the resolved mapping itself – which means that the output is a relative file path.

This function may throw an Error if:

  • the requested entry cannot be resolved (aka, not defined in the "exports" map)
  • an entry is defined but no known conditions were matched (see options.conditions)

pkg

Type: object Required: true

The package.json contents.

entry

Type: string Required: false Default: . (aka, root)

The desired target entry, or the original import path.

When entry is not a relative path (aka, does not start with '.'), then entry is given the './' prefix.

When entry begins with the package name (determined via the pkg.name value), then entry is truncated and made relative.

When entry is already relative, it is accepted as is.

Examples

Assume we have a module named "foobar" and whose pkg contains "name": "foobar".

| entry value | treated as | reason | |-|-|-| | null / undefined | '.' | default | | '.' | '.' | value was relative | | 'foobar' | '.' | value was pkg.name | | 'foobar/lite' | './lite' | value had pkg.name prefix | | './lite' | './lite' | value was relative | | 'lite' | './lite' | value was not relative & did not have pkg.name prefix |

imports(pkg, target, options?)

Returns: string[] or undefined

Traverse the "imports" within the contents of a package.json file. If the contents does not contain an "imports" map, then undefined will be returned.

Successful resolutions will always result in a string or string[] value. This will be the value of the resolved mapping itself – which means that the output is a relative file path.

This function may throw an Error if:

  • the requested target cannot be resolved (aka, not defined in the "imports" map)
  • an target is defined but no known conditions were matched (see options.conditions)

pkg

Type: object Required: true

The package.json contents.

target

Type: string Required: true

The target import identifier; for example, #hash or #hash/md5.

Import specifiers must begin with the # character, as required by the resolution specification. However, if target begins with the package name (determined by the pkg.name value), then resolve.exports will trim it from the target identifier. For example, "foobar/#hash/md5" will be treated as "#hash/md5" for the "foobar" package.

Options

The resolve(), imports(), and exports() functions share these options. All properties are optional and you are not required to pass an options argument.

Collectively, the options are used to assemble a list of conditions that should be activated while resolving your target(s).

Note: Although the Node.js documentation primarily showcases conditions alongside "exports" usage, they also apply to "imports" maps too. (example)

options.require

Type: boolean Default: false

When truthy, the "require" field is added to the list of allowed/known conditions. Otherwise the "import" field is added instead.

options.browser

Type: boolean Default: false

When truthy, the "browser" field is added to the list of allowed/known conditions. Otherwise the "node" field is added instead.

options.conditions

Type: string[] Default: []

A list of additional/custom conditions that should be accepted when seen.

Important: The order specified within options.conditions does not matter. The matching order/priority is always determined by the "exports" map's key order.

For example, you may choose to accept a "production" condition in certain environments. Given the following pkg content:

const pkg = {
  // package.json ...
  "exports": {
    "worker": "./$worker.js",
    "require": "./$require.js",
    "production": "./$production.js",
    "import": "./$import.mjs",
  }
};

resolve.exports(pkg, '.');
// Conditions: ["default", "import", "node"]
//=> ["./$import.mjs"]

resolve.exports(pkg, '.', {
  conditions: ['production']
});
// Conditions: ["default", "production", "import", "node"]
//=> ["./$production.js"]

resolve.exports(pkg, '.', {
  conditions: ['production'],
  require: true,
});
// Conditions: ["default", "production", "require", "node"]
//=> ["./$require.js"]

resolve.exports(pkg, '.', {
  conditions: ['production', 'worker'],
  require: true,
});
// Conditions: ["default", "production", "worker", "require", "node"]
//=> ["./$worker.js"]

resolve.exports(pkg, '.', {
  conditions: ['production', 'worker']
});
// Conditions: ["default", "production", "worker", "import", "node"]
//=> ["./$worker.js"]

options.unsafe

Type: boolean Default: false

Important: You probably do not want this option! It will break out of Node's default resolution conditions.

When enabled, this option will ignore all other options except options.conditions. This is because, when enabled, options.unsafe does not assume or provide any default conditions except the "default" condition.

resolve.exports(pkg, '.');
//=> Conditions: ["default", "import", "node"]

resolve.exports(pkg, '.', { unsafe: true });
//=> Conditions: ["default"]

resolve.exports(pkg, '.', { unsafe: true, require: true, browser: true });
//=> Conditions: ["default"]

In other words, this means that trying to use options.require or options.browser alongside options.unsafe will have no effect. In order to enable these conditions, you must provide them manually into the options.conditions list:

resolve.exports(pkg, '.', {
  unsafe: true,
  conditions: ["require"]
});
//=> Conditions: ["default", "require"]

resolve.exports(pkg, '.', {
  unsafe: true,
  conditions: ["browser", "require", "custom123"]
});
//=> Conditions: ["default", "browser", "require", "custom123"]

Legacy Resolver

Also included is a "legacy" method for resolving non-"exports" package fields. This may be used as a fallback method when for when no "exports" mapping is defined. In other words, it's completely optional (and tree-shakeable).

legacy(pkg, options?)

Returns: string or undefined

You may customize the field priority via options.fields.

When a field is found, its value is returned as written. When no fields were found, undefined is returned. If you wish to mimic Node.js behavior, you can assume this means 'index.js' – but this module does not make that assumption for you.

options.browser

Type: boolean or string Default: false

When truthy, ensures that the 'browser' field is part of the acceptable fields list.

Important: If your custom options.fields value includes 'browser', then your order is respected. Otherwise, when truthy, options.browser will move 'browser' to the front of the list, making it the top priority.

When true and "browser" is an object, then legacy() will return the the entire "browser" object.

You may also pass a string value, which will be treated as an import/file path. When this is the case and "browser" is an object, then legacy() may return:

  • false – if the package author decided a file should be ignored; or
  • your options.browser string value – but made relative, if not already

See the `"browser" field specification for more information.

options.fields

Type: string[] Default: ['module', 'main']

A list of fields to accept. The order of the array determines the priority/importance of each field, with the most important fields at the beginning of the list.

By default, the legacy() method will accept any "module" and/or "main" fields if they are defined. However, if both fields are defined, then "module" will be returned.

import { legacy } from 'resolve.exports';

// package.json
const pkg = {
  "name": "...",
  "worker": "worker.js",
  "module": "module.mjs",
  "browser": "browser.js",
  "main": "main.js",
};

legacy(pkg);
// fields = [module, main]
//=> "module.mjs"

legacy(pkg, { browser: true });
// fields = [browser, module, main]
//=> "browser.mjs"

legacy(pkg, {
  fields: ['missing', 'worker', 'module', 'main']
});
// fields = [missing, worker, module, main]
//=> "worker.js"

legacy(pkg, {
  fields: ['missing', 'worker', 'module', 'main'],
  browser: true,
});
// fields = [browser, missing, worker, module, main]
//=> "browser.js"

legacy(pkg, {
  fields: ['module', 'browser', 'main'],
  browser: true,
});
// fields = [module, browser, main]
//=> "module.mjs"

License

MIT © Luke Edwards