noDuplicateDependencies

JSON (and super languages)

Caution

This rule is part of the nursery group. This means that it is experimental and the behavior can change at any time.

Summary

• Rule available since: v2.2.4
• Diagnostic Category: lint/nursery/noDuplicateDependencies
• This rule doesn’t have a fix.
• The default severity of this rule is information.
• Sources:
  • Same as package-json/unique-dependencies
  • Same as package-json-dependencies/duplicate-dependencies

How to configure

biome.json

{
  "linter": {
    "rules": {
      "nursery": {
        "noDuplicateDependencies": "error"
      }
    }
  }
}

Description

Prevent the listing of duplicate dependencies. The rule supports the following dependency groups: “bundledDependencies”, “bundleDependencies”, “dependencies”, “devDependencies”, “overrides”, “optionalDependencies”, and “peerDependencies”.

Dependencies are not allowed to be listed twice under the same dependency group.

Examples

Invalid

{
    "dependencies": {
        "foo": "1.0.0",
        "foo": "2.0.0"
    }
}

{
    "bundleDependencies": ["foo", "foo"]
}

Valid

{
    "dependencies": {
        "foo": "2.0.0"
    }
}

{
    "bundleDependencies": ["foo"]
}

Some dependency group dependencies are checked against other dependency groups;

• Dependencies listed in “dependencies” cannot be listed under “devDependencies”, “optionalDependencies” or “peerDependencies”.
• Dependencies listed in “optionalDependencies” cannot be listed under “peerDependencies” (and vice versa).

Dependencies listed in “devDependencies” are allowed to be listed in “optionalDependencies” or “peerDependencies”. And dependencies listed in “overrides” & “bundleDependencies” are not checked against other dependency groups.

Examples

Invalid

{
    "dependencies": {
        "foo": "1.0.0"
    },
    "devDependencies": {
        "foo": "1.0.0"
    }
}

Valid

{
    "dependencies": {
        "foo": "1.0.0"
    }
}

Related links

• Disable a rule
• Configure the code fix
• Rule options
• Source Code
• Test Cases