node package manager

Introducing npm Enterprise add-ons. Integrate third-party dev tools into npm…


A consistent shrinkwrap tool


A consistent shrinkwrap tool

$ npm-shrinkwrap

This runs shrinkwrap, which verifies your package.json & node_modules tree are in sync. If they are it runs shrinkwrap then fixes the resolved fields and trims from fields

When you run npm-shrinkwrap it will either:

  • fail because your package.json & node_modules disagree, i.e. you installed something without --save or hand edited your package.json
  • succeed, and add all top level dependencies to your npm-shrinkwrap.json file and then runs npm-shrinkwrap sync which writes the npm-shrinkwrap.json back into node_modules

We need to verify that package.json, npm-shrinkwrap.json and node_modules all have the same content.

Currently npm verifies most things but doesn't verify git completely.

The edge case npm doesn't handle is if you change the tag in your package.json. npm happily says that the dependency in your node_modules tree is valid irregardless of what tag it is.

NPM shrinkwrap serializes your node_modules folder. Depending on whether you installed a module from cache or not it will either have or not have a resolved field.

npm-shrinkwrap will put a resolved field in for everything in your shrinkwrap.

There are a few tricks to ensuring there is no unneeded churn in the output of npm shrinkwrap.

This first is to ensure you install with npm cache clean so that an npm ls output is going to consistently give you the resolved and from fields.

The second is to just delete all from fields from the generated shrinkwrap file since they change a lot but are never used. However you can only delete some from fields, not all.

When you run shrinkwrap and check it into git you have an unreadable git diff.

npm-shrinkwrap comes with an npm-shrinkwrap diff command.

npm-shrinkwrap diff master HEAD
npm-shrinkwrap diff HEAD npm-shrinkwrap.json --short

You can use this command to print out a readable context specific diff of your shrinkwrap changes.

npm-shrinkwrap can be programmatically configured with an array of validators.

These validators run over every node in the shrinkwrap file and can do assertions.

Useful assertions are things like assertion all dependencies point at your private registry instead of the public one.

var npmShrinkwrap = require("npm-shrinkwrap");
    dirname: process.cwd()
}, function (err, optionalWarnings) {
    if (err) {
        throw err;
    optionalWarnings.forEach(function (err) {
    console.log("wrote npm-shrinkwrap.json")

npm-shrinkwrap algorithm

  • run npm ls to verify that node_modules & package.json agree.

  • run verifyGit() which has a similar algorithm to npm ls and will verify that node_modules & package.json agree for all git links.

  • read the old npm-shrinkwrap.json into memory

  • run npm shrinkwrap

  • copy over excess non-standard keys from old shrinkwrap into new shrinkwrap and write new shrinkwrap with extra keys to disk.

  • run setResolved() which will ensure that the new npm-shrinkwrap.json has a "resolved" field for every package and writes it to disk.

  • run trimFrom() which normalizes or removes the "from" field from the new npm-shrinkwrap.json. It also sorts the new npm-shrinkwrap.json deterministically then writes that to disk

  • run trimNested() which will trim any changes in the npm-shrinkwrap.json to dependencies at depth >=1. i.e. any changes to nested dependencies without changes to the direct parent dependency just get deleted

  • run sync() to the new npm-shrinkwrap.json back into the node_modules folder

npm-shrinkwrap NOTES:

  • verifyGit() only has a depth of 0, where as npm ls has depth infinity.

  • verifyGit() is only sound for git tags. This means that for non git tags it gives warnings / errors instead.

  • trimFrom() also sorts and rewrites the package.json for consistency

  • By default, the npm-shrinkwrap algorithm does not dedupe nested dependencies. This means that the shrinkwrap is closer to the installed dependencies by default. If this is not desired --keepNested=false can be passed to the shrinkwrap cli

npm install npm-shrinkwrap

npm test

  • Raynos