enforce-module-boundaries.md

Nx Enforce Module Boundaries

In this exercise you'll learn how to enforce architecture constraints. We will use the built-in eslint rule @nx/enforce-module-boundaries in order to configure how libraries are allowed to depend on each other.

1. Configure tags

The first thing we need to do is to tag our projects so that our eslint rule is able to treat them.

For each project, go ahead and assign the proper tag into the project.json file

Libraries in libs/movies/

• "tags": ["scope:movies", "type:feature"]
• "tags": ["scope:movies", "type:data-access"]
• "tags": ["scope:movies", "type:ui"]
• "tags": ["scope:movies", "type:util"]

Libraries in libs/shared/

• "tags": ["scope:shared", "type:feature"]
• "tags": ["scope:shared", "type:data-access"]
• "tags": ["scope:shared", "type:ui"]
• "tags": ["scope:shared", "type:util"]

2. Setup Scope Constraints

Let's setup constraints between different scopes.

Open the .eslintrc.json file in the root folder and locate the @nx/enforce-module-boundaries rule

// eslintrc.json

"rules": {
  "@nx/enforce-module-boundaries": [
    "error",
    {
      "enforceBuildableLibDependency": true,
      "allow": [],
      "depConstraints": [
        {
          "sourceTag": "*",
          "onlyDependOnLibsWithTags": ["*"]
        }
      ]
    }
  ]
}

Change its configuration so that scope:movie can only depend on scope:shared & scope:movie. Also scope:shared can only depend on scope:shared.

Solution

// eslintrc.json

[
  {
    "sourceTag": "scope:movies",
    "onlyDependOnLibsWithTags": ["scope:movies", "scope:shared"]
  },
  {
    "sourceTag": "scope:shared",
    "onlyDependOnLibsWithTags": ["scope:shared"]
  }
]

Great, go ahead and confirm that the rule you have applied is actually working.

Go to any file within the shared scope and try to import a file from the movie scope. If configured properly, your IDE should already warn you about something is wrong.

Run the lint command for affected projects to see if your changes break some rule or not.

nx affected:lint

3. Setup Type Constraints

Now let's introduce another dimension to our architecture enforcement ruleset. We are going to setup constraints within scopes & cross-scopes, between types.

Again open the eslintrc.json file and add the following rules:

• type feature can only depend on type feature, data-access, ui, util
• type data-access can only depend on type data-access, util
• type ui can only depend on type ui, util
• type util can only depend on type util

feature

Feature

// eslintrc.json

[
  {
    "sourceTag": "type:feature",
    "onlyDependOnLibsWithTags": ["type:feature", "type:data-access", "type:ui", "type:util"]
  },
]

Great, go ahead and confirm that the rule you have applied is actually working.

Go to any library of type ui and try to import a file from a library of type feature. If configured properly, your IDE should already warn you about something is wrong.

Run the lint command for affected projects to see if your changes break some rule or not.

nx affected:lint

data-access

data-access

// eslintrc.json

[
  {
    "sourceTag": "type:data-access",
    "onlyDependOnLibsWithTags": ["type:data-access", "type:util"]
  },
]

Great, go ahead and confirm that the rule you have applied is actually working.

Go to any library of type data-access and try to import a file from a library of type ui. If configured properly, your IDE should already warn you about something is wrong.

Run the lint command for affected projects to see if your changes break some rule or not.

nx affected:lint

ui

ui

// eslintrc.json

[
  {
    "sourceTag": "type:ui",
    "onlyDependOnLibsWithTags": ["type:ui", "type:util"]
  },
]

Great, go ahead and confirm that the rule you have applied is actually working.

Go to any library of type ui and try to import a file from a library of type data-access. If configured properly, your IDE should already warn you about something is wrong.

Run the lint command for affected projects to see if your changes break some rule or not.

nx affected:lint

util

util

// eslintrc.json

[
  {
    "sourceTag": "type:util",
    "onlyDependOnLibsWithTags": ["type:util"]
  }
]

Great, go ahead and confirm that the rule you have applied is actually working.

Go to any library of type ui and try to import a file from a library of type data-access. If configured properly, your IDE should already warn you about something is wrong.

Run the lint command for affected projects to see if your changes break some rule or not.

nx affected:lint

Congratulation, you have now enforced dependency constraints for your workspace architecture!