yarn-deduplicate
Advanced tools
The yarn-deduplicate package is a tool designed to optimize your Yarn lockfile by deduplicating dependencies. It helps to reduce the number of duplicate packages in your project, which can lead to smaller lockfiles and potentially fewer issues with dependency resolution.
Deduplicate Dependencies
This command scans your Yarn lockfile and removes duplicate dependencies, ensuring that each package is only included once. This can help to reduce the size of your lockfile and avoid potential conflicts.
yarn-deduplicateSpecify Strategy
This command allows you to specify a deduplication strategy. The 'fewer' strategy aims to reduce the number of different versions of a package to the minimum possible.
yarn-deduplicate --strategy fewerInteractive Mode
This command runs the deduplication process in interactive mode, allowing you to manually choose which versions of packages to keep.
yarn-deduplicate --interactivenpm-dedupe is a similar tool for the npm package manager. It removes duplicate packages from the npm lockfile, optimizing the dependency tree. Unlike yarn-deduplicate, which is specific to Yarn, npm-dedupe is designed for use with npm.
pnpm is a fast, disk space-efficient package manager that also handles deduplication of dependencies. It uses a different approach by creating a single version of each package in a global store, which is then linked to the project. This can lead to even more efficient deduplication compared to yarn-deduplicate.
Builds: 
Cleans up yarn.lock by removing duplicates.
A duplicate package is when two dependencies are resolved to a different version, even when a single version matches the range specified in the dependencies. See the Deduplication strategies section for a few examples.
Install the package globally:
npm install -g yarn-deduplicate
or
yarn global add yarn-deduplicate
This package also works wth npx, so you don't need to install it.
The most common scenario is to run
yarn-deduplicate yarn.lock
This will use the default strategy to remove duplicated packages in yarn.lock.
If you do not specify the yarn.lock path, it defaults to yarn.lock.
Check all available options with:
yarn-deduplicate --help
yarn.lock contains a list of all the dependencies required by your project (including transitive
dependencies), and the actual package version installed to satisfy those dependencies.
For the context of this project, a "duplicated package" is a package that appears on multiple nodes of the dependency tree with overlapping version ranges but resolved to different versions.
For example, imagine that your project directly depends on lodash and babel, and babel depends
on lodash as well. Specifically, your project depends on lodash@^1.0.0 and babel depends on
lodash@^1.1.0. Because how the resolution algorithm works in Yarn, you might end up with two
different copies of lodash (for example, version 1.0.1 and 1.2.0) in your project, even when
1.2.0 will suffice to satisfy both requirements for lodash. That's a "duplicated package".
It is important to note that we do not consider duplicated packages when the version ranges don't
overlap. For example, if your project depends on underscore@^1.0.0 and underscore@^2.0.0. Your
project will end up with two versions of underscore, and yarn-deduplicate won't change that.
When using yarn-deduplicate remember that it will change your dependency tree. There are
certain code paths that now will run with a different set of dependencies. It is highly recommended
that you review each change to yarn.lock. If the change is too big, use the flag --packages to
deduplicate them gradually.
Yarn documentation seems to suggest this package shouldn't be necessary. For example, in https://classic.yarnpkg.com/en/docs/cli/dedupe/, it says
The dedupe command isn’t necessary.
yarn installwill already dedupe.
This is, however, not exactly true. There are cases where yarn will not deduplicate existing packages. For example, this scenario:
Install libA. It depends on libB ^1.1.0. At this point, the latest version of libB is
1.1.2, so it gets installed as a transitive dependency in your repo
After a few days, install libC. It also depends on libB ^1.1.0. But this time, the latest
libB version is 1.1.3.
In the above scenario, you'll end up with libB@1.1.2 and libB@1.1.3 in your repo.
Find more examples in:
highest
It will try to use the highest installed version. For example, with the following yarn.lock:
library@^1.1.0:
version "1.2.0"
library@^1.2.0:
version "1.2.0"
library@^1.3.0:
version "1.3.0"
It will deduplicate library@^1.1.0 and library@^1.2.0 to 1.3.0
fewer
It will try to minimize the number of installed versions by trying to deduplicate to the version
that satisfies most of the ranges first. For example, with the following yarn.lock:
library@*:
version "2.0.0"
library@>=1.1.0:
version "3.0.0"
library@^1.2.0:
version "1.2.0"
It will deduplicate library@* and library@>=1.1.0 to 1.2.0.
Note that this will cause some packages to downgrade it version. Be sure to check the changelogs between all versions and understand the consequences of that downgrade. If unsure, don't use this strategy.
It is not recommended to use different strategies for different packages. There is no guarantee that
the strategy will be honored in subsequent runs of yarn-deduplicate unless the same set of flags
is specified again.
--packages <package1> <package2> <packageN>
Receives a list of packages to deduplicate. It will ignore any other duplicated package not in the
list. This option is recommended when the number of duplicated packages in yarn.lock is too big
to be easily reviewed by a human. This will allow for a more controlled and progressive
deduplication of yarn.lock.
In this version we have renamed the project and refactored the CLI. These are the equivalent commands:
# Old
npm install -g yarn-tools
# New
npm install -g yarn-deduplicate
# Old
yarn-tools list-duplicates path/to/yarn.lock
# New
yarn-deduplicate --list path/to/yarn.lock
# Old
yarn-tools fix-duplicates path/to/yarn.lock > tmp
mv tmp path/to/yarn.lock
# New
yarn-deduplicate path/to/yarn.lock
# Old
yarn-tools fix-duplicates path/to/yarn.lock package1 package2
# New
yarn-deduplicate --packages package1,package2 path/to/yarn.lock
Pull requests, issues and comments welcome. For pull requests:
See the existing issues for things to start contributing.
For bigger changes, make sure you start a discussion first by creating an issue and explaining the intended change.
Atlassian requires contributors to sign a Contributor License Agreement, known as a CLA. This serves as a record stating that the contributor is entitled to contribute the code/documentation/translation to the project and is willing to have it used in distributions and derivative works (or is willing to transfer ownership).
Prior to accepting your contributions we ask that you please follow the appropriate link below to digitally sign the CLA. The Corporate CLA is for those who are contributing as a member of an organization and the individual CLA is for those contributing as an individual.
Copyright (c) 2017 Atlassian and others. Apache 2.0 licensed, see LICENSE.txt file.
2.0.0- 2020-02-29
FAQs
Deduplication tool for yarn.lock files
The npm package yarn-deduplicate receives a total of 293,995 weekly downloads. As such, yarn-deduplicate popularity was classified as popular.
We found that yarn-deduplicate demonstrated a not healthy version release cadence and project activity because the last version was released a year ago. It has 1 open source maintainer collaborating on the project.
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