Manypkg is a linter for package.json files in Yarn, Bolt or pnpm monorepos.

manypkg check runs all of the checks against your repo, logs any errors and exits with a code

manypkg fix runs all of the checks against your repo and fixes any of problems that can be fixed.

manypkg run executes scripts for packages within a monorepo.

As an example, let's say there are two packages: @project/package-a at packages/pkg-a and @project/package-b at packages/pkg-a which both have a start script, manypkg run can be used like this:

The following wouldn't work though because the package and pkg aren't unique among the package names/directories:

manypkg exec executes a command for all packages within a monorepo.

As an example, let's say there are two packages which both have a dist dir, manypkg exec can be used like this:

The ranges for all dependencies(excluding peerDependencies) on external packages should exactly match(===). It's important to note that this check does not enforce that only a single version of an external package is installed, only that two versions of an external package will never be installed because they're specified as dependencies of internal packages.

So that only a single version of an external package will be installed because having multiple versions of the same package can cause confusion and bundle size problems especially with libraries like React that require there to only be a single copy of the library.

The highest range of the dependency is set as the range at every non-peer dependency place it is depended on.

Incorrect example

package.json

packages/pkg-a/package.json

packages/pkg-b/package.json

This example will cause an error because the range 1.0.0 for some-external-package specified in @manypkg-example/pkg-a is not equal(===) to the range 2.0.0 specified in @manypkg-example/pkg-b.

Correct example

package.json

packages/pkg-a/package.json

packages/pkg-b/package.json

This example will not cause an error because the range 1.0.0 for some-external-package specified in @manypkg-example/pkg-a is equal(===) to the range 1.0.0 specified in @manypkg-example/pkg-b.

There are some cases where you might want to intentionally have conflicts between versions. To do this, you can use something that isn't a valid semver range instead of a range such as a git url or etc. If you'd like a conflicting version of an npm package, you can use npm:pkg-name@your-range-here instead of just a range and it will be ignored.

The ranges for all regular dependencies, devDependencies and optionalDependencies(not peerDependencies) on internal packages should include the version of the internal package.

So that an internal package that depends on another internal package will always get the local version of the internal package rather than a version from the registry because installing internal packages from the registry can be very confusing since you generally expect to get the local version when you depend on an internal package.

If the range is a caret range or a tilde range with no other comparators, the range is set as a caret or tilde range respectively with the version of the internal package. If it is any other range, the range is set to the exact version of the internal package.

All peerDependencies should also be specified in devDependencies and the range specified in devDependencies should be a subset of the range for that dependency in peerDependencies.

This is so that peerDependencies are available in the package during development for testing and etc.

The range for the dependency specified in peerDependencies is added to devDependencies unless the package is already a non-peer dependency elsewhere in the repo in which, that range is used instead.

The root package should not have any devDependencies, instead all dependencies should be in dependencies

The root package.json of a monorepo is not published so whether a dependency is in devDependencies or dependencies does not make a difference and having one place to put dependencies in the root means that people do not have to arbitrarily decide where a dependency should go every time they install one.

All devDependencies in the root package.json are moved to dependencies.

A dependency shouldn't be specified in more than one of dependencies, devDependencies or optionalDependencies.

The dep is removed from devDependencies or optionalDependencies if it's also in dependencies, if it's in devDependencies and optionalDependencies, it is removed from dependencies.

There are rules from npm about what a package name can be and a package will fail to publish if those rules are not met.

All packages will be published together so some packages may depend on a package which can't be published. Checking for invalid package names prevents this kind of publish failure.

This requires manual fixing as automatically fixing this may lead to valid but incorrect package names.

Dependencies in the dependency fields(dependencies, devDependencies, peerDependencies, optionalDependencies) should be sorted alphabetically.

When you add a package with yarn add or etc. dependencies are sorted, and this can cause confusing diffs if the dependencies were not previously sorted.

This is fixed by sorting deps by key alphabetically.

If a GitHub repo URL is in the repository field in the root package.json, all of the packages should have a repository field which goes into the directory of the package.

Having a repository field is helpful so there is a link to the source of a package on npm but setting that field on every package and making sure it's correct is error prone and time consuming.

This is fixed by setting the correct URL.