install-from

Reliably installs a local package into another, for testing.

It’s very similar to installing a published package; npm pack is used to generate a tarball that only includes published files, which are extracted into node_modules for a similar result to a regular npm install --no-save.

npm link is a notoriously unreliable way to locally test a package in another package, as it uses symlinks:

• It will not reveal if the package.json files field or .npmignore is correct, as npm link doesn’t use npm pack like npm publish does.
• As the package being tested is not actually installed inside the node_modules of the package it’s being tested in, peer dependencies installed in the host package can’t be reached. For example, this makes it difficult to test a package that has a react peer dependency inside a Next.js project.
• How it works is not intuitive. It messes with the global node_modules and bin directories, and you have to remember to use npm unlink to tidy up, which inconveniently strips the dependency from your package.json.

Setup

Installation isn’t required to use the CLI command install-from with npx.

To install with npm, run:

npm install install-from --save-dev

Then, use either the CLI command install-from or the JS API function installFrom.

CLI

Command install-from

Reliably installs a local package into another at the CWD, for testing.

Arguments

Argument	Description
1	Absolute or CWD relative filesystem path to the package to install from.

Examples

Installing a local package into another using npx.

In a terminal, change to the directory of the package you want to test another package in:

cd ~/Repos/foo

Then, install the desired local package:

npx install-from ~/Repos/bar

API

function installFrom

Reliably installs a local package into another, for testing.

Parameter	Type	Description
pathPackageFrom	string	Absolute or CWD relative filesystem path to the package to install from.
pathPackageTo	string?	Absolute or CWD relative filesystem path to the package to install to, defaulting to process.cwd().

Returns: Promise<void> — Resolves once installation is complete.

Examples

How to import.

import installFrom from 'install-from';

Installing a local package into another.

installFrom(
  './packages/package-to-install-from',
  './packages/package-to-install-to'
)
  .then(() => {
    // …
  })
  .catch(() => {
    // …
  });