Migrate to moon

Now that we've talked about the workspace, projects, tasks, and more, we must talk about something important... Should you embrace moon tasks? Or keep using language/ecosystem specific scripts? Or both (incremental adoption)?

Migrate to moon tasks

We suggest using moon tasks (of course), as they provide far more granular control and configurable options than scripts, and a moon.yml is a better source of truth. Scripts aren't powerful enough to scale for large codebases.

An example of what this may look like can be found below. This may look like a lot, but it pays dividends in the long run.

<project>/moon.yml

language: 'javascript'

fileGroups:
  sources:
    - 'src/**/*'
  tests:
    - 'tests/**/*'

tasks:
  build:
    command: 'webpack build --output-path @out(0)'
    inputs:
      - '@globs(sources)'
      - 'webpack.config.js'
    outputs:
      - 'build'
  dev:
    command: 'webpack server'
    inputs:
      - '@globs(sources)'
      - 'webpack.config.js'
    local: true
  format:
    command: 'prettier --check .'
    inputs:
      - '@globs(sources)'
      - '@globs(tests)'
      - '/prettier.config.js'
  lint:
    command: 'eslint .'
    inputs:
      - '@globs(sources)'
      - '@globs(tests)'
      - '.eslintignore'
      - '.eslintrc.js'
      - '/.eslintrc.js'
  test:
    command: 'jest .'
    inputs:
      - '@globs(sources)'
      - '@globs(tests)'
      - 'jest.config.js'
  typecheck:
    command: 'tsc --build'
    inputs:
      - '@globs(sources)'
      - '@globs(tests)'
      - 'tsconfig.json'
      - '/tsconfig.json'

To ease the migration process, we offer the moon migrate from-package-json command, which will convert a project's package.json scripts into moon.yml tasks, while also determining project dependencies (dependsOn). This needs to be ran per project.

$ moon migrate from-package-json <project>

This command will do its best to parse and convert scripts, but this isn't always a simple 1:1 conversion, especially when determining dependency chains. For this reason alone, we suggest manually curating tasks, but the migrate command well get you most of the way!

Continue using scripts

As a frontend developer you're already familiar with the Node.js ecosystem, specifically around defining and using package.json scripts, and you may not want to deviate from this. Don't worry, simply enable the node.inferTasksFromScripts setting to automatically create moon tasks from a project's scripts! These can then be ran with moon run.

This implementation is a simple abstraction that runs npm run <script> (or pnpm/yarn) in the project directory as a child process. While this works, relying on package.json scripts incurs the following risks and disadvantages:

• Inputs default to **/*:
  • A change to every project relative file will mark the task as affected, even those not necessary for the task. Granular input control is lost.
  • A change to workspace relative files will not mark the task as affected. For example, a change to /prettier.config.js would not be detected for a npm run format script.
• Outputs default to an empty list unless:
  • moon will attempt to extract outputs from arguments, by looking for variations of --out, --outFile, --dist-dir, etc.
  • If no output could be determined, builds will not be cached and hydrated.
• Tasks will always run in CI unless:
  • moon will attempt to determine invalid CI tasks by looking for popular command usage, for example: webpack serve, next dev, --watch usage, and more. This is not an exhaustive check.
  • The script name contains variations of dev, start, or serve.

Next steps

By this point, you should have a better understanding behind moon's fundamentals! Why not adopt incrementally next? Jump into guides for advanced use cases or concepts for a deeper understanding.

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