.TH "NPM\-SHRINKWRAP" "1" "October 2016" "" ""
.SH "NAME"
\fBnpm-shrinkwrap\fR \- Lock down dependency versions
.SH SYNOPSIS
.P
.RS 2
.nf
npm shrinkwrap
.fi
.RE
.SH DESCRIPTION
.P
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 \fBpackage\.json\fP file is still
required if you want to use \fBnpm install\fP\|\.
.P
By default, \fBnpm install\fP recursively installs the target's
dependencies (as specified in \fBpackage\.json\fP), 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 \fBpackage\.json\fP 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\.
.P
As an example, consider package A:
.P
.RS 2
.nf
{
  "name": "A",
  "version": "0\.1\.0",
  "dependencies": {
    "B": "<0\.1\.0"
  }
}
.fi
.RE
.P
package B:
.P
.RS 2
.nf
{
  "name": "B",
  "version": "0\.0\.1",
  "dependencies": {
    "C": "<0\.1\.0"
  }
}
.fi
.RE
.P
and package C:
.P
.RS 2
.nf
{
  "name": "C",
  "version": "0\.0\.1"
}
.fi
.RE
.P
If these are the only versions of A, B, and C available in the
registry, then a normal \fBnpm install A\fP will install:
.P
.RS 2
.nf
A@0\.1\.0
`\-\- B@0\.0\.1
    `\-\- C@0\.0\.1
.fi
.RE
.P
However, if B@0\.0\.2 is published, then a fresh \fBnpm install A\fP will
install:
.P
.RS 2
.nf
A@0\.1\.0
`\-\- B@0\.0\.2
    `\-\- C@0\.0\.1
.fi
.RE
.P
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\.
.P
In this case, A's author can run
.P
.RS 2
.nf
npm shrinkwrap
.fi
.RE
.P
This generates \fBnpm\-shrinkwrap\.json\fP, which will look something like this:
.P
.RS 2
.nf
{
  "name": "A",
  "version": "0\.1\.0",
  "dependencies": {
    "B": {
      "version": "0\.0\.1",
      "from": "B@^0\.0\.1",
      "resolved": "https://registry\.npmjs\.org/B/\-/B\-0\.0\.1\.tgz",
      "dependencies": {
        "C": {
          "version": "0\.0\.1",
          "from": "org/C#v0\.0\.1",
          "resolved": "git://github\.com/org/C\.git#5c380ae319fc4efe9e7f2d9c78b0faa588fd99b4"
        }
      }
    }
  }
}
.fi
.RE
.P
The shrinkwrap command has locked down the dependencies based on
what's currently installed in node_modules\.  When \fBnpm install\fP
installs a package with an \fBnpm\-shrinkwrap\.json\fP in the package
root, the shrinkwrap file (rather than \fBpackage\.json\fP files) completely
drives the installation of that package and all of its dependencies
(recursively)\.  So now the author publishes A@0\.1\.0, and subsequent
installs of this package will use B@0\.0\.1 and C@0\.0\.1, regardless the
dependencies and versions listed in A's, B's, and C's \fBpackage\.json\fP
files\.
.SS Using shrinkwrapped packages
.P
Using a shrinkwrapped package is no different than using any other
package: you can \fBnpm install\fP it by hand, or add a dependency to your
\fBpackage\.json\fP file and \fBnpm install\fP it\.
.SS Building shrinkwrapped packages
.P
To shrinkwrap an existing package:
.RS 0
.IP 1. 3
Run \fBnpm install\fP in the package root to install the current
versions of all dependencies\.
.IP 2. 3
Validate that the package works as expected with these versions\.
.IP 3. 3
Run \fBnpm shrinkwrap\fP, add \fBnpm\-shrinkwrap\.json\fP to git, and publish
your package\.

.RE
.P
To add or update a dependency in a shrinkwrapped package:
.RS 0
.IP 1. 3
Run \fBnpm install\fP in the package root to install the current
versions of all dependencies\.
.IP 2. 3
Add or update dependencies\. \fBnpm install\fP each new or updated
package individually and then update \fBpackage\.json\fP\|\.  Note that they
must be explicitly named in order to be installed: running \fBnpm
install\fP with no arguments will merely reproduce the existing
shrinkwrap\.
.IP 3. 3
Validate that the package works as expected with the new
dependencies\.
.IP 4. 3
Run \fBnpm shrinkwrap\fP, commit the new \fBnpm\-shrinkwrap\.json\fP, and
publish your package\.

.RE
.P
You can use npm help outdated to view dependencies with newer versions
available\.
.SS Other Notes
.P
A shrinkwrap file must be consistent with the package's \fBpackage\.json\fP
file\. \fBnpm shrinkwrap\fP 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 \fBpackage\.json\fP), since that would
indicate that \fBpackage\.json\fP is not correct\.
.P
Since \fBnpm shrinkwrap\fP is intended to lock down your dependencies for
production use, \fBdevDependencies\fP will not be included unless you
explicitly set the \fB\-\-dev\fP flag when you run \fBnpm shrinkwrap\fP\|\.  If
installed \fBdevDependencies\fP 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 \fBdependencies\fP instead\.
.P
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\.
.SS Caveats
.P
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\.
.SH SEE ALSO
.RS 0
.IP \(bu 2
npm help install
.IP \(bu 2
npm help 5 package\.json
.IP \(bu 2
npm help ls

.RE