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Project graph

The project graph is a representation of all configured projects in the workspace and their relationships between each other, and is represented internally as a directed acyclic graph (DAG). Below is a visual representation of a project graph, composed of multiple applications and libraries, where both project types depend on libraries.

info

The moon project-graph command can be used to view the structure of your workspace.

Relationships​

A relationship is between a dependent (downstream project) and a dependency/requirement (upstream project). Relationships are derived from source code and configuration files within the repository, and fall into 1 of 2 categories:

Explicit​

These are dependencies that are explicitly defined in a project's moon.yml config file, using the dependsOn setting.

moon.yml
dependsOn:
  - 'components'
  - id: 'utils'
    scope: 'peer'

Implicit​

These are dependencies that are implicitly discovered by moon when scanning the repository. How an implicit dependency is discovered is based on a language's platform integration, and how that language's ecosystem functions.

package.json
{
  // ...
  "dependencies": {
    "@company/components": "workspace:*"
  },
  "peerDependencies": {
    "@company/utils": "workspace:*"
  }
}
caution

If a language is not officially supported by moon, then implicit dependencies will not be resolved. For unsupported languages, you must explicitly configure dependencies.

Scopes​

Every relationship is categorized into a scope that describes the type of relationship between the parent and child. Scopes are currently used for project syncing and deep Docker integration.

  • Production - Dependency is required in production, will not be pruned in production environments, and will sync as a production dependency.
  • Development - Dependency is required in development and production, will be pruned from production environments, and will sync as a development-only dependency.
  • Build - Dependency is required for building only, and will sync as a build dependency.
  • Peer - Dependency is a peer requirement, with language specific semantics. Will sync as a peer dependency when applicable.

What is the graph used for?​

Great question, the project graph is used throughout the codebase to accomplish a variety of functions, but mainly:

  • Is fed into the task graph to determine relationships of tasks between other tasks, and across projects.
  • Powers our Docker layer caching and scaffolding implementations.
  • Utilized for project syncing to ensure a healthy repository state.
  • Determines affected projects in continuous integration workflows.