npm shrinkwrap
This command locks down the versions of a package's dependencies so
that you can control exactly which versions of each dependency will be
used when your package is installed. The package.json file is still
required if you want to use npm install.
By default, npm install recursively installs the target's
dependencies (as specified in package.json), choosing the latest
available version that satisfies the dependency's semver pattern. In
some situations, particularly when shipping software where each change
is tightly managed, it's desirable to fully specify each version of
each dependency recursively so that subsequent builds and deploys do
not inadvertently pick up newer versions of a dependency that satisfy
the semver pattern. Specifying specific semver patterns in each
dependency's package.json would facilitate this, but that's not always
possible or desirable, as when another author owns the npm package.
It's also possible to check dependencies directly into source control,
but that may be undesirable for other reasons.
As an example, consider package A:
{
"name": "A",
"version": "0.1.0",
"dependencies": {
"B": "<0.1.0"
}
}
package B:
{
"name": "B",
"version": "0.0.1",
"dependencies": {
"C": "<0.1.0"
}
}
and package C:
{
"name": "C",
"version": "0.0.1"
}
If these are the only versions of A, B, and C available in the
registry, then a normal npm install A will install:
A@0.1.0
`-- B@0.0.1
`-- C@0.0.1
However, if B@0.0.2 is published, then a fresh npm install A will
install:
A@0.1.0
`-- B@0.0.2
`-- C@0.0.1
assuming the new version did not modify B's dependencies. Of course, the new version of B could include a new version of C and any number of new dependencies. If such changes are undesirable, the author of A could specify a dependency on B@0.0.1. However, if A's author and B's author are not the same person, there's no way for A's author to say that he or she does not want to pull in newly published versions of C when B hasn't changed at all.
In this case, A's author can run
npm shrinkwrap
This generates npm-shrinkwrap.json, which will look something like this:
{
"name": "A",
"version": "1.1.0",
"dependencies": {
"B": {
"version": "1.0.1",
"from": "B@^1.0.0",
"resolved": "https://registry.npmjs.org/B/-/B-1.0.1.tgz",
"dependencies": {
"C": {
"version": "1.0.1",
"from": "org/C#v1.0.1",
"resolved": "git://github.com/org/C.git#5c380ae319fc4efe9e7f2d9c78b0faa588fd99b4"
}
}
}
}
}
The shrinkwrap command has locked down the dependencies based on what's
currently installed in node_modules. The installation behavior is changed to:
The module tree described by the shrinkwrap is reproduced. This means reproducing the structure described in the file, using the specific files referenced in "resolved" if available, falling back to normal package resolution using "version" if one isn't.
The tree is walked and any missing dependencies are installed in the usual fashion.
Using a shrinkwrapped package is no different than using any other
package: you can npm install it by hand, or add a dependency to your
package.json file and npm install it.
To shrinkwrap an existing package:
npm install in the package root to install the current
versions of all dependencies.npm shrinkwrap, add npm-shrinkwrap.json to git, and publish
your package.To add or update a dependency in a shrinkwrapped package:
npm install in the package root to install the current
versions of all dependencies.npm install --save each new or updated
package individually to update the package.json and the shrinkwrap.
Note that they must be explicitly named in order to be installed: running
npm install with no arguments will merely reproduce the existing
shrinkwrap.npm-shrinkwrap.json, and publish your package.You can use npm-outdated to view dependencies with newer versions available.
A shrinkwrap file must be consistent with the package's package.json
file. npm shrinkwrap will fail if required dependencies are not
already installed, since that would result in a shrinkwrap that
wouldn't actually work. Similarly, the command will fail if there are
extraneous packages (not referenced by package.json), since that would
indicate that package.json is not correct.
Since npm shrinkwrap is intended to lock down your dependencies for
production use, devDependencies will not be included unless you
explicitly set the --dev flag when you run npm shrinkwrap. If
installed devDependencies are excluded, then npm will print a
warning. If you want them to be installed with your module by
default, please consider adding them to dependencies instead.
If shrinkwrapped package A depends on shrinkwrapped package B, B's shrinkwrap will not be used as part of the installation of A. However, because A's shrinkwrap is constructed from a valid installation of B and recursively specifies all dependencies, the contents of B's shrinkwrap will implicitly be included in A's shrinkwrap.
If you wish to lock down the specific bytes included in a package, for example to have 100% confidence in being able to reproduce a deployment or build, then you ought to check your dependencies into source control, or pursue some other mechanism that can verify contents rather than versions.
Last modified January 08, 2016 Found a typo? Send a pull request!