no-private.md

boundaries/no-private

Prevent importing private elements of another element

Rule details

This rule follow the next principles:

• An element becomes private when it is under another element.
• Private elements can't be used by anyone except its parent. (and any other descendant of the parent when allowUncles option is enabled)
• Private elements can import public elements.
• Private elements can import another private element when both have the same parent ("brother elements")
• Private elements can import another private element if it is a direct child of a common ancestor, and the allowUncles option is enabled.

Options

"boundaries/no-private": [<enabled>, { "allowUncles": <boolean>, "message": <string> }]

• enabled: for enabling the rule. 0=off, 1=warn, 2=error.
• allowUncles: Optional. If set to false, it disallows importing "uncle elements". Default is true.
• message: Custom message for the rule errors. Note that the rule default message provides enough information about why the error was produced, so you should define a custom message only if you are sure about what you are doing. Read "error messages" for further information.

Options example

{
  "rules": {
    "boundaries/no-private": [2, { "allowUncles": true }]
  }
}

Settings

Examples in the next sections are based on the previous options example and these files and settings.

src/
└── modules/
    ├── module-a/
    │   ├── index.js
    │   └── ModuleA.js
    └── module-b/
        ├── index.js
        ├── ModuleB.js
        └── modules
            ├── module-c
            │   ├── index.js
            │   ├── ModuleC.js
            │   └── modules
            │       └── module-e
            │           ├── index.js
            │           └── ModuleE.js
            └── module-d
                ├── index.js
                └── ModuleD.js

{
  "settings": {
    "boundaries/elements": [
      {
        "type": "modules",
        "pattern": "modules/*",
        "mode": "folder"
      }
    ],
    "import/resolver": {
      "babel-module": {}
    }
  }
}

Some of the next examples are written as is the project has configured a babel alias for the folder src/modules. This is made for better readability of the examples, but it would work also with relative paths. You can configure the plugin to recognize babel aliases using eslint-import-resolver-babel-module as a resolver, as you can see in the settings example.

Examples of incorrect code for this rule:

module-a can't import module-c because it is child of module-b

// src/modules/module-a/moduleA.js
import ModuleC from 'modules/module-b/modules/module-c'

module-b can't import module-e because it is child of module-c (even when it is his grandchild)

// src/modules/module-b/moduleB.js
import ModuleE from './modules/module-c/modules/module-e'

module-e can't import module-d when allowUncles option is disabled

// src/modules/module-b/modules/module-c/modules/module-e/ModuleE
import ModuleD from 'modules/module-b/modules/module-d'

Examples of correct code for this rule:

module-b can import module-c because it is his direct child

// src/modules/module-b/ModuleB.js
import ModuleC from './modules/module-c'

module-c can import module-a because it is public

// src/modules/module-b/modules/module-c/ModuleC.js
import ModuleA from 'modules/module-a'

module-c can import module-d because it is his brother

// modules/module-b/modules/module-c/ModuleC.js
import ModuleD from '../module-d'

module-e can import module-d because it is his uncle

// modules/module-b/modules/module-c/modules/module-e/ModuleE
import ModuleD from 'modules/module-b/modules/module-d'

Error messages

This rule provides information about the parent element of the imported one in case it is private, e.g. Dependency is private of element of type 'modules' with elementName 'module-b'

You can also configure a custom error message for changing this default behaviour, or even custom error messages only for a specific rule option. Read "error messages" in the main docs for further info about how to configure messages.

Further reading

Read how to configure the boundaries/elements setting to assign an element type to each project's file.