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Dependencies are an intrinsic part of every software project.

The Dependencies component is responsible to track the list of dependencies a project has, and then used by project types as the model for rendering project-specific dependency manifests such as the dependencies section package.json files.

To add a dependency you can use a project-type specific API such as nodeProject.addDeps() or use the generic API of project.deps:

project.deps.addDependency(dep, type);

Dependencies can often be specified on the options for the project type, such as:

const project = new cdk.JsiiProject({
// ...
deps: ['constructs', 'projen'],

By default, npx projen will automatically install dependencies in your project if they are not already installed.

Semantic Requirements

The first argument (dep) is a string in the form MODULE[@VERSION] where MODULE is the package-manager specific name of the dependency (i.e. for node projects, this is the npm module name) and VERSION is an optional semantic version requirement (e.g. @^7).


Regardless of which type of project and package manager you use, whether it by Python/PyPi, Node.js/NPM, Java/Maven, this method for defining dependencies will always be the same.

Dependency Types

The second argument (type) defines the dependency type and is one of:

  • DependencyType.RUNTIME: The dependency is required for the program/library during runtime.
  • DependencyType.PEER: The dependency is required at runtime but only a single copy of the module must exist in the dependency closure of the consumer. In most package managers (PyPI, NuGet, Maven) there is no difference between runtime and peer dependencies (since all dependencies are installed as peers), but in npm, this is an important distinction. Prior to npm@7, peer dependencies must be installed explicitly by consumers.
  • DependencyType.BUNDLED: A runtime dependency that is bundled and shipped with the module, so consumers are not required to install it.
  • DependencyType.BUILD: The dependency is required to run the build task.
  • DependencyType.TEST: The dependency is required to run the test task.
  • DependencyType.DEVENV: The dependency is required for development (e.g. IDE plugins).

Overriding Dependency Specifications

If a dependency is added multiple times, the last specification will prevail. This allows you to override dependency specs added by projects or components.

For example, if you wish to change the version of the TypeScript compiler used in TypeScript projects:

const { typescript } = require('projen');

const project = new typescript.TypeScriptProject({
/* ... */