namespaceDeclarations

Reports using legacy namespace declarations.

✅ This rule is included in the ts logical preset.

Namespaces are a legacy feature of TypeScript that can lead to confusion and are not compatible with ECMAScript modules. Modern codebases generally use export and import statements to define and use ECMAScript modules instead.

Examples

❌ Incorrect

namespace Values {
  export const value = 123;
}

namespace Fruits {
  export const apple = "🍎";
}

✅ Correct

export const value = 123;

export const Fruits = {
  apple: "🍎",
};

Options

allowDeclarations

Whether to allow namespaces declared with the declare keyword.

ts.rules({
  namespaceDeclarations: {
    allowDeclarations: true,
  },
});

❌ Incorrect

namespace Values {
  export const value = 123;
}

✅ Correct

declare namespace Values {
  const value: number;
}

allowDefinitionFiles

ts.rules({
  namespaceDeclarations: {
    allowDefinitionFiles: true,
  },
});

Whether to allow namespaces in .d.ts and other definition files.

❌ Incorrect

index.ts

declare namespace Values {
  const value: number;
}

✅ Correct

index.d.ts

declare namespace Values {
  const value: number;
}

When Not To Use It

If your project uses TypeScript’s CommonJS export syntax (export = ...), you may need to use namespaces in order to export types from your module. You can learn more about this at:

• TypeScript#52203, the pull request introducing verbatimModuleSyntax
• TypeScript#60852, an issue requesting syntax to export types from a CommonJS module.

If your project uses this syntax, either because it was architected before modern modules and namespaces, or because a module option such as verbatimModuleSyntax requires it, it may be difficult to migrate off of namespaces. In that case you may not be able to use this rule for parts of your project.

You might consider using Flint disable comments and/or configuration file disables for those specific situations instead of completely disabling this rule.

Further Reading

• TypeScript handbook entry on Modules
• TypeScript handbook entry on Namespaces
• TypeScript handbook entry on Namespaces and Modules

Equivalents in Other Linters

• Biome: noNamespace
• Deno: no-namespace
• ESLint: @typescript-eslint/no-namespace
• Oxlint: typescript/no-namespace