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Using Builders

Builders perform actions on your code. This can include building, linting, testing, serving and many other actions.

There are two main differences between a builder and a shell script or an npm script:

  1. Builders encourage a consistent methodology for performing similar actions on unrelated projects. i.e. A developer switching between teams can be confident that nx build project2 will build project2 with the default settings, just like nx build project1 built project1.
  2. Nx can leverage this consistency to perform the same builder command across multiple projects. i.e. nx affected --target==test will run the test builder command on every project that is affected by the current code change.

Builder Command Definitions

The builder commands that are available for each project are defined and configured in the /workspace.json file.

{
  "projects": {
    "cart": {
      "root": "apps/cart",
      "sourceRoot": "apps/cart/src",
      "projectType": "application",
      "schematics": {},
      "architect": {
        "build": {
          "builder": "@nrwl/web:build",
          "options": {
            "outputPath": "dist/apps/cart",
            ...
          },
          "configurations": {
            "production": {
              "sourceMap": false,
              ...
            }
          }
        },
        "test": {
          "builder": "@nrwl/jest:jest",
          "options": {
            ...
          }
        }
      }
    }
  }
}

Each project has its builder commands defined in the architect property. In this snippet, cart has two builder commands defined - build and test.

Note: build and test can be any strings you choose. For the sake of consistency, we make test run unit tests for every project and build produce compiled code for the projects which can be built.

Each builder command definition has a builder property and, optionally, an options and a configurations property.

  • builder is a string of the from [package name]:[builder name]. For the build builder, the package name is @nrwl/web and the builder name is build.
  • options is an object that contains any configuration defaults for the builder. These options vary from builder to builder.
  • configurations allows you to create presets of options for different scenarios. All the configurations start with the properties defined in options as a baseline and then overwrite those options. In the example, there is a production configuration that overrides the default options to set sourceMap to false.

Executing Builder Commands

The nx run cli command (or the shorthand versions) can be used to execute builder commands.

nx run [project]:[command]
nx run cart:build

As long as your command name doesn't conflict with an existing nx cli command, you can use this short hand:

nx [command] [project]
nx build cart

You can also use a specific configuration preset like this:

nx [command] [project] --configuration=[configuration]
nx build cart --configuration=production

Or you can overwrite individual builder options like this:

nx [command] [project] --[optionNameInCamelCase]=[value]
nx build cart --outputPath=some/other/path

See Also