@darkobits/is-dev
v0.6.3
Published
Check if your package is being installed locally or by another package.
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Maintainers
Readme
This package provides a way to determine if your package is being installed locally (ex: npm install
)
or by another package (ex: npm install <your package>
).
Installation
$ npm install @darkobits/is-dev
Usage
This package is designed to be used as part of a lifecycle script or in files that run during lifecycle
scripts. It provides a function, isDev
, and two binaries, if-dev
and if-not-dev
.
isDev(): boolean
Returns true
if the package is the host package, false
if it is a dependency or if the package is
installed globally.
postinstall.js
import isDev from '@darkobits/is-dev';
if (isDev()) {
// This package is the host package.
} else {
// This package is a dependency.
}
Binaries
if-dev
checks if the package is the host package. If it is, the provided command will be executed.
package.json
{
"scripts": {
"bar": "cowsay 'Moo!'",
"foo": "if-dev npm run bar"
}
}
if-not-dev
is the inverse of if-dev
.
Use Cases
NPM runs the following lifecycle scripts (among others) in the following order:
| Script | Runs | Typical Use Case |
|---------------|----------------------------------|-----------------------------------------------|
| install
| Always | Set up package for use by consuming packages. |
| postinstall
| Always | See above. |
| prepare
| Development (npm install
) Only | Generate package's build artifacts. |
Because modern JavaScript projects have begun to rely heavily on transpilation, this order of execution
is less than ideal. If, for example, we are developing a package that uses a postinstall
script that
must be transpiled, it will not have been built when the install
and postinstall
lifecycle scripts
are run.
Take the following package.json
snippet, for example:
{
"files": [
"dist"
],
"scripts": {
"build": "babel src --out-dir dist",
"prepare": "npm run build",
"postinstall": "./dist/bin/postinstall.js"
}
}
This will work fine for consumers of our package, who will only be downloading our build artifacts
(re: dist
). But when we try to run npm install
when this package is the host, we will get an error,
because the package has not been prepared yet, and our dist
folder does not exist.
We can use if-dev
to address this problem:
package.json
{
"scripts": {
"build": "babel src --out-dir dist",
"prepare": "npm run build",
"postinstall": "if-dev npm run prepare && ./dist/postinstall.js"
}
}
This will ensure that for local development, the package is prepared before we try to execute
postinstall.js
. When the package is being installed by consumers, if-dev
will simply no-op and
postinstall.js
will be run immediately.
Alternatively, imagine we have a postinstall
script that we don't want to run during local
development. We can use if-not-dev
to no-op the postinstall
script/command unless the package is
being installed by a consumer:
{
"scripts": {
"build": "babel src --out-dir dist",
"prepare": "npm run build",
"postinstall": "if-not-dev ./dist/postinstall.js"
}
}