nx-core.md

Using Nx Core Without Plugins

The core of Nx is generic, simple, and unobtrusive. Nx plugins, although very useful for many projects, are completely optional. Most large Nx workspaces use plugins for some things and don't use plugins for others.

This guide will walk you through creating a simple Nx workspace with no plugins. It will help you see what capabilities of Nx are completely generic and can be used with any technology or tool.

Using Nx Core

Creating a New Workspace

Running npx create-nx-workspace@latest --preset=core creates an empty workspace.

This is what is generated:

packages/
nx.json
workspace.json
tsconfig.base.json
package.json

package.json contains Nx packages.

{
  "name": "myorg",
  "version": "0.0.0",
  "license": "MIT",
  "scripts": {},
  "private": true,
  "devDependencies": {
    "nx": "12.8.0",
    "@nrwl/workspace": "12.8.0",
    "@types/node": "14.14.33",
    "typescript": "~4.3.5"
  }
}

nx.json contains the Nx CLI configuration.

{
  "extends": "@nrwl/workspace/presets/core.json",
  "npmScope": "myorg",
  "tasksRunnerOptions": {
    "default": {
      "runner": "@nrwl/workspace/tasks-runners",
      "options": {
        "cacheableOperations": ["build", "lint", "test", "e2e"]
      }
    }
  }
}

Creating an NPM Package

Running nx g npm-package simple results in:

packages/
 simple/
   index.js
   package.json
nx.json
workspace.json
tsconfig.base.json
package.json

The generated simple/package.json:

{
  "name": "@myorg/simple",
  "version": "1.0.0",
  "scripts": {
    "test": "node index.js"
  }
}

With this you can invoke any script defined in packages/simple/package.json via Nx. For instance, you can invoke the test script by running nx test simple. And if you invoke this command a second time, the results are retrieved from cache.

In this example, we used a generator to create the package, but you could have also created it by hand or copied it from another project.

Creating Second NPM Package and Enabling Yarn Workspaces

Running nx g npm-package complex results in:

packages/
 simple/
   index.js
   package.json
 complex/
   index.js
   package.json
nx.json
workspace.json
tsconfig.base.json
package.json

Now let's modify packages/complex/index.js to include require('@myorg/simple'). If you run nx test complex, you will see an error saying that @myorg/simple cannot be resolved.

This is expected. Nx analyzes your source to enable computation caching, it knows what projects are affected by your PR, but it does not change how your npm scripts run. Whatever tools you use in your npm scripts will run exactly as they would without Nx. Nx Core doesn't replace your tools and doesn't change how they work.

In this simple setup, Nx doesn't do any automated path mapping as it usually does, but rather fully relies on a corresponding yarn or npm workspaces setup. As such, at the root-level package.json you should have something like:

{
  ...
  "workspaces": [
    "packages/*"
  ]
}

Moreover, a dependency from complex to simple in packages/complex/package.json needs to be added:

{
  "name": "@myorg/complex",
  "version": "1.0.0",
  "scripts": {
    "test": "node index.js"
  },
  "dependencies": {
    "@myorg/simple": "*"
  }
}

Finally, run yarn install or npm install to make the package available in the yarn/npm workspace.

Running nx test complex should work now.

Using Yarn/PNPM/Lerna

This example uses Yarn to connect the two packages. Most of the time, however, there are better ways to do it. The React, Node and Angular plugins for Nx allow different projects in your workspace to import each other without having to maintain cumbersome package.json files. Instead, they use Webpack, Rollup and Jest plugins to enable this use case in a more elegant way. Read about the relationship between Nx and Yarn/Lerna/PNPM.

What Nx Core Provides

Nx Understands How Your Workspace Is Structured

If you run nx graph you will see that complex has a dependency on simple. Any change to simple will invalidate the computation cache for complex, but changes to complex won't invalidate the cache for simple.

In contrast to more basic monorepo tools, Nx doesn't just analyze package.json files. It does much more. Nx also knows that adding a require() creates a dependency and that some dependencies cannot even be expressed in the source code.

Nx Orchestrates Tasks

Running nx run-many --target=test --all will test all projects in parallel.

Often, tests for different projects can run independently, but builds can't. If you, say, have two applications app1 and app2 depending on the shared-components library, it's possible that the library has to be built first before the two applications can be built. And that's what nx run-many --target=build --projects=app1,app2 will do.

With Nx, you never have to worry about preparing your workspace before running a particular command. Nx will do it for you.

Nx Knows What Is Affected

Running nx affected --target=test will test all the projects affected by the current PR.

Nx Caches and Distributes Tasks

Running nx run-many --target=build --all will cache the file artifacts and the terminal output, so if you run it again the command will execute instantly because the results will be retrieved from cache. If you use Nx Cloud the cache will be shared between you, your teammates, and the CI agents. Nx can also distribute tasks across multiple machines while preserving the developer experience of running it on a single machine.

This works because Nx's computation caching and distributed task execution work on the process level. It doesn't matter what build means. It can be an npm script, a custom Nx executor, a Gradle task. Nx will handle it in the same way.

Adding Plugins

As you can see, the core of Nx is generic, simple, and unobtrusive. Nx Plugins are completely optional, but they can really level up your developer experience. Watch this video to see the plugins in action.

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