120 lines
3.4 KiB
Plaintext
120 lines
3.4 KiB
Plaintext
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---
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description: 'Disallow magic numbers.'
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---
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> 🛑 This file is source code, not the primary documentation location! 🛑
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>
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> See **https://typescript-eslint.io/rules/no-magic-numbers** for documentation.
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This rule extends the base [`eslint/no-magic-numbers`](https://eslint.org/docs/rules/no-magic-numbers) rule.
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It adds support for:
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- numeric literal types (`type T = 1`),
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- `enum` members (`enum Foo { bar = 1 }`),
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- `readonly` class properties (`class Foo { readonly bar = 1 }`).
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## Options
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This rule adds the following options:
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```ts
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interface Options extends BaseNoMagicNumbersOptions {
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ignoreEnums?: boolean;
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ignoreNumericLiteralTypes?: boolean;
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ignoreReadonlyClassProperties?: boolean;
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ignoreTypeIndexes?: boolean;
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}
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const defaultOptions: Options = {
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...baseNoMagicNumbersDefaultOptions,
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ignoreEnums: false,
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ignoreNumericLiteralTypes: false,
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ignoreReadonlyClassProperties: false,
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ignoreTypeIndexes: false,
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};
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```
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### `ignoreEnums`
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A boolean to specify if enums used in TypeScript are considered okay. `false` by default.
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Examples of **incorrect** code for the `{ "ignoreEnums": false }` option:
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```ts option='{ "ignoreEnums": false }' showPlaygroundButton
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enum foo {
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SECOND = 1000,
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}
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```
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Examples of **correct** code for the `{ "ignoreEnums": true }` option:
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```ts option='{ "ignoreEnums": true }' showPlaygroundButton
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enum foo {
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SECOND = 1000,
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}
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```
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### `ignoreNumericLiteralTypes`
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A boolean to specify if numbers used in TypeScript numeric literal types are considered okay. `false` by default.
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Examples of **incorrect** code for the `{ "ignoreNumericLiteralTypes": false }` option:
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```ts option='{ "ignoreNumericLiteralTypes": false }' showPlaygroundButton
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type SmallPrimes = 2 | 3 | 5 | 7 | 11;
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```
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Examples of **correct** code for the `{ "ignoreNumericLiteralTypes": true }` option:
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```ts option='{ "ignoreNumericLiteralTypes": true }' showPlaygroundButton
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type SmallPrimes = 2 | 3 | 5 | 7 | 11;
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```
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### `ignoreReadonlyClassProperties`
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Examples of **incorrect** code for the `{ "ignoreReadonlyClassProperties": false }` option:
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```ts option='{ "ignoreReadonlyClassProperties": false }' showPlaygroundButton
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class Foo {
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readonly A = 1;
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readonly B = 2;
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public static readonly C = 1;
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static readonly D = 1;
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}
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```
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Examples of **correct** code for the `{ "ignoreReadonlyClassProperties": true }` option:
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```ts option='{ "ignoreReadonlyClassProperties": true }' showPlaygroundButton
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class Foo {
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readonly A = 1;
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readonly B = 2;
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public static readonly C = 1;
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static readonly D = 1;
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}
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```
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### `ignoreTypeIndexes`
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A boolean to specify if numbers used to index types are okay. `false` by default.
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Examples of **incorrect** code for the `{ "ignoreTypeIndexes": false }` option:
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```ts option='{ "ignoreTypeIndexes": false }' showPlaygroundButton
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type Foo = Bar[0];
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type Baz = Parameters<Foo>[2];
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```
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Examples of **correct** code for the `{ "ignoreTypeIndexes": true }` option:
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```ts option='{ "ignoreTypeIndexes": true }' showPlaygroundButton
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type Foo = Bar[0];
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type Baz = Parameters<Foo>[2];
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```
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## When Not To Use It
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If your project frequently deals with constant numbers and you don't wish to take up extra space to declare them, this rule might not be for you.
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We recommend at least using descriptive comments and/or names to describe constants.
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You might consider using [ESLint disable comments](https://eslint.org/docs/latest/use/configure/rules#using-configuration-comments-1) instead of completely disabling this rule.
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