noImportCycles

JavaScript (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: v2.0.0
• Diagnostic Category: lint/nursery/noImportCycles
• This rule doesn’t have a fix.
• The default severity of this rule is warning.
• This rule belongs to the following domains:
  • project
• Sources:
  • Same as import/no-cycle

Description

Prevent import cycles.

This rule warns when a file imports another file that, either directly or indirectly, imports the original file again.

Cycles can lead to symbols that are unexpectedly undefined and are generally considered poor code hygiene.

If a cycle is detected, it is advised to move code such that imports only go in a single direction, i.e. they don’t point “back” to the importing file.

Note

This rule is computationally expensive. If you are particularly pressed for lint time, or don’t think you have an issue with dependency cycles, you may not want this rule enabled.

Examples

Invalid

foobar.js

import { baz } from "./baz.js";

export function foo() {
    baz();
}

export function bar() {
    console.log("foobar");
}

baz.js

import { bar } from "./foobar.js";

export function baz() {
    bar();
}

Valid

foo.js

import { baz } from "./baz.js";

export function foo() {
    baz();
}

bar.js

export function bar() {
    console.log("foobar");
}

baz.js

import { bar } from "./bar.js";

export function baz() {
    bar();
}

types.ts

import type { bar } from "./qux.ts";

export type Foo = {
  bar: typeof bar;
};

qux.ts

import type { Foo } from "./types.ts";

export function bar(foo: Foo) {
    console.log(foo);
}

Options

The rule provides the options described below.

ignoreTypes

Ignores type-only imports when finding an import cycle. A type-only import (import type) will be removed by the compiler, so it cuts an import cycle at runtime. Note that named type imports (import { type Foo }) aren’t considered as type-only because it’s not removed by the compiler if the verbatimModuleSyntax option is enabled. Enabled by default.

{
  "options": {
    "ignoreTypes": false
  }
}

Invalid

types.ts

import type { bar } from "./qux.ts";

export type Foo = {
  bar: typeof bar;
};

qux.ts

import type { Foo } from "./types.ts";

export function bar(foo: Foo) {
    console.log(foo);
}

How to configure

biome.json

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

Related links

• Disable a rule
• Configure the code fix
• Rule options