useValidNamespaceImports (JavaScript)

Language JavaScript (and super languages)

Summary

Rule available since: v2.6.8
Diagnostic Category: lint/nursery/useValidNamespaceImports
This rule doesn’t have a fix.
The default severity of this rule is error.
This rule belongs to the following domains:
- project
Sources:
- Same as import/namespace

How to configure

1
{
2
  "linter": {
3
    "rules": {
4
      "nursery": {
5
        "useValidNamespaceImports": "error"
6
      }
7
    }
8
  }
9
}

Description

Require that names read from a namespace import are exported by the imported module.

A namespace import, such as import * as utils from "./utils.js", puts every export of a module into one object. Reading a name that the module doesn’t export gives undefined, which usually means the name has a typo, or the export was renamed or removed.

This rule reports:

reading a name from a namespace import that the imported module doesn’t export, including names read through destructuring, such as const { name } = utils, and JSX elements, such as <Components.Button />;
assigning a value to a member of a namespace import, which throws an error at runtime because namespace imports are read-only;
namespace imports and export * as name from statements of a module that has no exports.

The rule also follows namespaces that a module exports, such as export * as helpers from "./helpers.js", so utils.helpers.missing is checked as well.

The rule only checks modules that use import or export statements. It skips CommonJS modules and TypeScript modules that use export =, because their exports can’t be determined reliably.

Note that if you use TypeScript, you probably don’t need this rule, since TypeScript already reports these mistakes.

Examples

Invalid

1
export const add = (a, b) => a + b;

1
import * as utils from "./utils.js";
2

3
utils.subtract(2, 1);

/invalid-read.js:3:7 lint/nursery/useValidNamespaceImports ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━

  ✖ The namespace utils has no export named subtract.
  
    1 │ import * as utils from "./utils.js";
    2 │ 
  > 3 │ utils.subtract(2, 1);
      │       ^^^^^^^^
    4 │ 
  
  ℹ Reading a name that a module doesn't export gives undefined.
  
  ℹ Check the spelling of the name, or export it from the module.
  
  ℹ This rule belongs to the nursery group, which means it is not yet stable and may change in the future. Visit https://biomejs.dev/linter/#nursery for more information.

1
import * as utils from "./utils.js";
2

3
const { subtract } = utils;

/invalid-destructuring.js:3:9 lint/nursery/useValidNamespaceImports ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━

  ✖ The namespace utils has no export named subtract.
  
    1 │ import * as utils from "./utils.js";
    2 │ 
  > 3 │ const { subtract } = utils;
      │         ^^^^^^^^
    4 │ 
  
  ℹ Reading a name that a module doesn't export gives undefined.
  
  ℹ Check the spelling of the name, or export it from the module.
  
  ℹ This rule belongs to the nursery group, which means it is not yet stable and may change in the future. Visit https://biomejs.dev/linter/#nursery for more information.

1
import * as utils from "./utils.js";
2

3
utils.add = () => 0;

/invalid-assignment.js:3:1 lint/nursery/useValidNamespaceImports ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━

  ✖ The members of the namespace utils can't be reassigned.
  
    1 │ import * as utils from "./utils.js";
    2 │ 
  > 3 │ utils.add = () => 0;
      │ ^^^^^^^^^
    4 │ 
  
  ℹ Namespace imports are read-only, so this assignment throws an error at runtime.
  
  ℹ To change a value that a module exports, export a function from that module that changes it.
  
  ℹ This rule belongs to the nursery group, which means it is not yet stable and may change in the future. Visit https://biomejs.dev/linter/#nursery for more information.

Valid

1
export const add = (a, b) => a + b;

1
import * as utils from "./utils.js";
2

3
utils.add(2, 1);
4
const { add } = utils;