pacote

What is pacote?

Pacote is a Node.js library that provides a set of utilities for fetching and extracting npm packages. It is designed to handle various types of package sources, including the npm registry, tarballs, git repositories, and local directories. Pacote is often used internally by npm and other tools to manage package dependencies.

What are pacote's main functionalities?

Fetch Package Metadata

This feature allows you to fetch the metadata of a package from the npm registry. The code sample demonstrates how to fetch and log the metadata for the 'lodash' package.

const pacote = require('pacote');

async function fetchMetadata(packageName) {
  const manifest = await pacote.manifest(packageName);
  console.log(manifest);
}

fetchMetadata('lodash');

Extract Package Tarball

This feature allows you to fetch and extract the tarball of a package. The code sample demonstrates how to fetch the tarball for the 'lodash' package and save it to a file named 'lodash.tgz'.

const pacote = require('pacote');
const fs = require('fs');

async function extractTarball(packageName, destination) {
  const tarballStream = await pacote.tarball.stream(packageName);
  tarballStream.pipe(fs.createWriteStream(destination));
}

extractTarball('lodash', './lodash.tgz');

Fetch Package from Git Repository

This feature allows you to fetch a package directly from a git repository. The code sample demonstrates how to fetch and log the metadata for the 'lodash' package from its GitHub repository.

const pacote = require('pacote');

async function fetchFromGit(repoUrl) {
  const manifest = await pacote.manifest(repoUrl);
  console.log(manifest);
}

fetchFromGit('https://github.com/lodash/lodash.git');

Other packages similar to pacote

npm

The npm package itself provides functionalities for managing npm packages, including installing, updating, and removing packages. While npm is a full-fledged package manager, pacote focuses specifically on fetching and extracting packages.

yarn

Yarn is another package manager for JavaScript that offers similar functionalities to npm, including package fetching and dependency management. Yarn also provides a more deterministic dependency resolution compared to npm.

pnpm

pnpm is a fast, disk space-efficient package manager. It uses a content-addressable file system to store all files from all module directories on a disk. While pnpm focuses on efficient package management, pacote is more specialized in fetching and extracting packages.

README

pacote

JavaScript Package Handler

USAGE

const pacote = require('pacote')

// get a package manifest
pacote.manifest('foo@1.x').then(manifest => console.log('got it', manifest))

// extract a package into a folder
pacote.extract('github:npm/cli', 'some/path', options)
  .then(({from, resolved, integrity}) => {
    console.log('extracted!', from, resolved, integrity)
  })

pacote.tarball('https://server.com/package.tgz').then(data => {
  console.log('got ' + data.length + ' bytes of tarball data')
})

Anything that you can do to with kind of package, you can do to any kind of package. Data that isn't relevant (like a packument for a tarball) will be simulated.

CLI

This module exports a command line interface that can do most of what is described below. Run pacote -h to learn more.

Pacote - The JavaScript Package Handler, v10.1.1

Usage:

  pacote resolve <spec>
    Resolve a specifier and output the fully resolved target
    Returns integrity and from if '--long' flag is set.

  pacote manifest <spec>
    Fetch a manifest and print to stdout

  pacote packument <spec>
    Fetch a full packument and print to stdout

  pacote tarball <spec> [<filename>]
    Fetch a package tarball and save to <filename>
    If <filename> is missing or '-', the tarball will be streamed to stdout.

  pacote extract <spec> <folder>
    Extract a package to the destination folder.

Configuration values all match the names of configs passed to npm, or
options passed to Pacote.  Additional flags for this executable:

  --long     Print an object from 'resolve', including integrity and spec.
  --json     Print result objects as JSON rather than node's default.
             (This is the default if stdout is not a TTY.)
  --help -h  Print this helpful text.

For example '--cache=/path/to/folder' will use that folder as the cache.

API

The spec refers to any kind of package specifier that npm can install. If you can pass it to the npm CLI, you can pass it to pacote. (In fact, that's exactly what the npm CLI does.)

See below for valid opts values.

• pacote.resolve(spec, opts) Resolve a specifier like foo@latest or github:user/project all the way to a tarball url, tarball file, or git repo with commit hash.

• pacote.extract(spec, dest, opts) Extract a package's tarball into a destination folder. Returns a promise that resolves to the {from,resolved,integrity} of the extracted package.

• pacote.manifest(spec, opts) Fetch (or simulate) a package's manifest (basically, the package.json file, plus a bit of metadata). See below for more on manifests and packuments. Returns a Promise that resolves to the manifest object.

• pacote.packument(spec, opts) Fetch (or simulate) a package's packument (basically, the top-level package document listing all the manifests that the registry returns). See below for more on manifests and packuments. Returns a Promise that resolves to the packument object.

• pacote.tarball(spec, opts) Get a package tarball data as a buffer in memory. Returns a Promise that resolves to the tarball data Buffer, with from, resolved, and integrity fields attached.

• pacote.tarball.file(spec, dest, opts) Save a package tarball data to a file on disk. Returns a Promise that resolves to {from,integrity,resolved} of the fetched tarball.

• pacote.tarball.stream(spec, streamHandler, opts) Fetch a tarball and make the stream available to the streamHandler function.

  This is mostly an internal function, but it is exposed because it does provide some functionality that may be difficult to achieve otherwise.

  The streamHandler function MUST return a Promise that resolves when the stream (and all associated work) is ended, or rejects if the stream has an error.

  The streamHandler function MAY be called multiple times, as Pacote retries requests in some scenarios, such as cache corruption or retriable network failures.

Options

• cache Where to store cache entries and temp files. Passed to cacache. Defaults to the same cache directory that npm will use by default, based on platform and environment.
• where Base folder for resolving relative file: dependencies.
• resolved Shortcut for looking up resolved values. Should be specified if known.
• integrity Expected integrity of fetched package tarball. If specified, tarballs with mismatched integrity values will raise an EINTEGRITY error.
• umask Permission mode mask for extracted files and directories. Defaults to 0o22. See "Extracted File Modes" below.
• fmode Minimum permission mode for extracted files. Defaults to 0o666. See "Extracted File Modes" below.
• dmode Minimum permission mode for extracted directories. Defaults to 0o777. See "Extracted File Modes" below.
• log A logger object with methods for various log levels. Typically, this will be npmlog in the npm CLI use case, but if not specified, the default is a logger that emits 'log' events on the process object.
• preferOnline Prefer to revalidate cache entries, even when it would not be strictly necessary. Default false.
• enjoyBy When picking a manifest from a packument, only consider packages published before the specified date. Default null.
• tag The default dist-tag to use when choosing a manifest from a packument. Defaults to latest.
• registry The npm registry to use by default. Defaults to https://registry.npmjs.org/.

Extracted File Modes

Files are extracted with a mode matching the following formula:

( (tarball entry mode value) | (minimum mode option) ) ~ (umask)

This is in order to prevent unreadable files or unlistable directories from cluttering a project's node_modules folder, even if the package tarball specifies that the file should be inaccessible.

It also prevents files from being group- or world-writable without explicit opt-in by the user, because all file and directory modes are masked against the umask value.

So, a file which is 0o771 in the tarball, using the default fmode of 0o666 and umask of 0o22, will result in a file mode of 0o755:

(0o771 | 0o666) => 0o777
(0o777 ~ 0o22) => 0o755

In almost every case, the defaults are appropriate. To respect exactly what is in the package tarball (even if this makes an unusable system), set both dmode and fmode options to 0. Otherwise, the umask config should be used in most cases where file mode modifications are required, and this functions more or less the same as the umask value in most Unix systems.

Extracted File Ownership

When running as root on Unix systems, all extracted files and folders will have their owning uid and gid values set to match the ownership of the containing folder.

This prevents root-owned files showing up in a project's node_modules folder when a user runs sudo npm install.

Manifests

A manifest is similar to a package.json file. However, it has a few pieces of extra metadata, and sometimes lacks metadata that is inessential to package installation.

In addition to the common package.json fields, manifests include:

• manifest._resolved The tarball url or file path where the package artifact can be found.

• manifest._from A normalized form of the spec passed in as an argument.

• manifest._integrity The integrity value for the package artifact.

• manifest.dist Registry manifests (those included in a packument) have a dist object. Only tarball is required, though at least one of shasum or integrity is almost always present.

  • tarball The url to the associated package artifact. (Copied by Pacote to manifest._resolved.)
  • integrity The integrity SRI string for the artifact. This may not be present for older packages on the npm registry. (Copied by Pacote to manifest._integrity.)
  • shasum Legacy integrity value. Hexadecimal-encoded sha1 hash. (Converted to an SRI string and copied by Pacote to manifest._integrity when dist.integrity is not present.)
  • fileCount Number of files in the tarball.
  • unpackedSize Size on disk of the package when unpacked.
  • npm-signature A signature of the package by the npmregistry Keybase account. (Obviously only present for packages published to https://registry.npmjs.org.)

Packuments

A packument is the top-level package document that lists the set of manifests for available versions for a package.

When a packument is fetched with accept: application/vnd.npm.install-v1+json in the HTTP headers, only the most minimum necessary metadata is returned. Additional metadata is returned when fetched with only accept: application/json.

For Pacote's purposes, the following fields are relevant:

• versions An object where each key is a version, and each value is the manifest for that version.
• dist-tags An object mapping dist-tags to version numbers. This is how foo@latest gets turned into foo@1.2.3.
• time In the full packument, an object mapping version numbers to publication times, for the opts.enjoyBy functionality.