Npm postinstall only on development

Question

I have npm module with following package.json

{
  "name": "my-app",
  "version": "0.0.0",
  "scripts": {
    "prepublish": "bower install",
    "build": "gulp"
  },
  "dependencies": {
    "express": "~4.0.0",
    "body-parser": "~1.0.1"
  },
  "devDependencies": {
    "gulp": "~3.6.0",
    "bower": "~1.3.2"
  }
}

When I deploy my app to production, I don't want install devDependecies, so, I run npm install --production. But in this case, prepublish script is called, but it doesn't need to, because I use CDN links in production.

How to call postinstall script only after npm install but not after npm install --production?

score 41 · Accepted Answer · answered Apr 03 '18 at 11:59

41

Newer npm (& Yarn) versions include support for the prepare script that is run after each install run but only in development mode. Also, the prepublish is deprecated. This should be enough:

{
  scripts: {
    "prepare": "bower install"
  }
}

Docs: https://docs.npmjs.com/misc/scripts

answered Apr 03 '18 at 11:59

mgol

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It appears later versions of npm (e.g. v6 and v7) run `prepare` on both dev and production installs now. – jchook Jul 12 '21 at 21:44
6

Yes, this answer is wrong. The npm script prepare does run in both prod and dev modes. – José Cabo Jan 31 '22 at 21:21
2

npm totally botched this :face_palm – Nick Feb 24 '22 at 22:43
1

With yarn this works perfectly! – MEMark Apr 11 '22 at 05:41
I forked and created https://www.npmjs.com/package/@znemz/skip-npm-task to specifically deal with this problem. – Nick Feb 15 '23 at 21:39

score 26 · Answer 2 · edited Jun 04 '21 at 13:59

26

I think you cannot choose what scripts are run based on the --production argument. What you can do, however, is supply a script which tests the NODE_ENV variable and only runs bower install if it's not "production".

If you are always in a unix-y environment, you can do it like this:

{ 
  scripts: {
    "prepublish": "[ \"$NODE_ENV\" = production ] && exit 0; bower install"
  }
}

edited Jun 04 '21 at 13:59

Nik Sumeiko

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answered Jan 06 '15 at 18:16

Sam Mikes

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nice answer! what if i want to also include "beta" enviroment? how can i add the "production OR beta" condition? – maephisto Apr 17 '15 at 09:20
Then it starts to get complicated -- but you can do `"[ \"$NODE_ENV\" = production ] || [ \"$NODE_ENV\" = beta ] || bower install"` – Sam Mikes Apr 17 '15 at 12:37
6

My NPM fails if I have this script and run it in production mode, as it returns a non-zero exit code. It works with: `[ \"$npm_config_production\" ] && exit 0; bower install` or `[ \"$NODE_ENV\" == production ] && exit 0; bower install` – Tim Jun 21 '16 at 13:44
I think it worth updating this answer based on last comment @SamMikes – Restuta Oct 09 '19 at 22:04
1

I think it would be even better if this answer reommended [cross-env](https://npmjs.com/package/cross-env) instead of using bash-only constructs. It's really actually easier and your build will be cross-platform. – Stijn de Witt Jul 13 '21 at 11:28

score 17 · Answer 3 · edited Apr 19 '16 at 15:31

17

This only works if you're on a unix-like environment:

NPM sets an environment variable to "true" when install is run with --production. To only run the postinstall script if npm install was not run with --production, use the following code.

"postinstall": "if [ -z \"$npm_config_production\" ]; then node_modules/gulp/bin/gulp.js first-run; fi",

edited Apr 19 '16 at 15:31

Samuel Bolduc

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answered May 05 '15 at 16:59

Synthe

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4

Thanks! I used the reverse for building assets only on heroku deploys: `"postinstall": "if [ -n \"$npm_config_production\" ]; then npm run build-for-production; fi"` – Derek Dahmer Jul 31 '15 at 18:12

score 13 · Answer 4 · answered Nov 11 '16 at 15:28

13

Solution that is less dependent on unix nature of your shell:

  "scripts": {
    "postinstall": "node -e \"process.env.NODE_ENV != 'production' && process.exit(1)\" || echo do dev stuff"
  },

answered Nov 11 '16 at 15:28

Alexey Vishentsev

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This fails when I add this module to another module as a dependency and try to `npm install` the encompassing one. Modifying the return value of the command chain fixes this for me: `"(node -e \"process.env.NODE_ENV !== 'production' && process.exit()\" && grunt devTask) || node -v"` – mucaho Apr 10 '17 at 12:49
1

FYI: This still works in 2022 and it was the only one-liner solution for me – ghaschel Sep 26 '22 at 19:36

score 12 · Answer 5 · answered Jan 03 '17 at 18:05

I work with windows, osx and linux so I use a NON environment specific solution to solve this problem:

In the postinstall handler i execute a js script that checks process.env.NODE_ENV variable and does the work.

in my specific case I have to execute a gulp task only in development env:

part of package.json

"scripts": {
  "postinstall": "node postinstall"
}

all postinstall.js script

if (process.env.NODE_ENV === 'development') {
  const gulp = require('./gulpfile');
  gulp.start('taskname');
}

last row of gulpfile.js

module.exports = gulp;

it's important to export gulp from the gulpfile.js because all tasks are in that specific gulp instance.

score 6 · Answer 6 · answered Nov 10 '18 at 13:24

I have a more general problem - where I want to skip running the postinstall script on local (direct) installs - like when I'm developing the package and run yarn add --dev my-new-dependency.

This is what I came up with. It works with both npm and yarn.

postinstall.js:

const env = process.env;
if (
    // if INIT_CWD (yarn/npm install invocation path) and PWD
    // are the same, then local (dev) install/add is taking place
    env.INIT_CWD === env.PWD ||
    // local (dev) yarn install may have been run
    // from a project subfolder
    env.INIT_CWD.indexOf(env.PWD) === 0
) {
    console.info('Skipping `postinstall` script on local installs');
}
else {
    // do post-installation things
    // ...
}

package.json:

"script": {
    "postinstall": "node postinstall.js",
    ...

Thanks, just what I was looking for. Created a npm package to do just that: https://www.npmjs.com/package/skip-local-postinstall — matthiasgiger, Sep 05 '20 at 18:44
Matthias your package looks great but it would be great to have flags cause I actually need this inverted. — Nick, Feb 24 '22 at 22:51

score 5 · Answer 7 · answered Sep 04 '18 at 14:29

Landed here because I had the same issue. Ended up with a solution that tests for the existence of a package under node_modules that I know should only be available in development.

{
  "scripts": {
    "postinstall": "bash -c '[ -d ./node_modules/@types ] && lerna run prepare || echo No postinstall without type info'" 
  }
}

This works fine for me conceptually, as the prepare scripts here called by lerna are mainly to ts-to-js compilations.

score 1 · Answer 8 · answered Jan 10 '18 at 13:35

1

I'm using if-env module. It's less verbose.

PS: I didn't test it on windows yet.

Install with:

npm i if-env

than in package.json scripts:

"postinstall-production": "echo \"production, skipping...\"",
"postinstall-dev": "echo \"doing dev exclusive stuff\"",
"postinstall": "if-env NODE_ENV=production && npm run postinstall-production || npm run postinstall-dev"

answered Jan 10 '18 at 13:35

JacopKane

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Does this mean that `if-env` has to be in `dependencies` instead of `devDependencies`? – jordanbtucker Aug 16 '18 at 02:19

Npm postinstall only on development

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