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‎stack/eslint-plugin/README.md‎

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Please see [that project's documentation](https://www.npmjs.com/package/@rushstack/eslint-config)
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for details. To learn about Rush Stack, please visit: [https://rushstack.io/](https://rushstack.io/)
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## `@rushstack/no-null`
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### `@rushstack/no-null`
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Prevents usage of JavaScript's `null` keyword.
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Prevent usage of JavaScript's `null` keyword.
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### Rule Details
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#### Rule Details
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Most programming languages have a "null" or "nil" value that serves several purposes:
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in type annotations. Comparisons with `null` are also allowed. In other words, this rule aims to tolerate
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preexisting null values but prevents new ones from being introduced.
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### Examples
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#### Examples
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The following patterns are considered problems when `@rushstack/no-null` is enabled:
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x = 0;
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}
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```
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### `@rushstack/no-untyped-underscore`
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(Optional) Prevent TypeScript code from accessing legacy JavaScript members whose name has an underscore prefix.
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#### Rule Details
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JavaScript does not provide a straightforward way to restrict access to object members, so API names commonly
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use an underscore prefix to indicate a private member (e.g. `exampleObject._privateMember`). However, inexperienced
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developers may not be aware of this convention. In TypeScript we can generally solve this problem by marking the types
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as `private` or omitting them from the typings. However, when migrating a large legacy code base to TypeScript,
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it may be difficult to author typings for every legacy API. For this case, you can enable the
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`@rushstack/no-untyped-underscore` rule.
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This rule reports access to members whose name has an underscore prefix, EXCEPT in cases where:
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- The containing object has a type which declares the member; OR
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- The untyped expression uses privileged names like `this._example` or `that._example` or `super._example`; OR
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#### Examples
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The following patterns are considered problems when `@rushstack/no-untyped-underscore` is enabled:
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```ts
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let x: any;
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x._privateMember = 123; // error
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let x: { [key: string]: number };
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x._privateMember = 123; // error
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```
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The following patterns are NOT considered problems:
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```ts
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let x: { _privateMember: any };
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x._privateMember = 123; // okay because _privateMember is declared by x's type
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enum E {
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_PrivateMember
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}
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let e: E._PrivateMember = E._PrivateMember; // okay because _PrivateMember is declared by E
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```

‎stack/eslint-plugin/src/no-null.ts‎

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},
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schema: [ ],
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docs: {
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description: 'Prevents usage of JavaScript\'s "null" keyword.',
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description: 'Prevent usage of JavaScript\'s "null" keyword',
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category: 'Stylistic Issues',
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recommended: "error",
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url: 'https://www.npmjs.com/package/@rushstack/eslint-config'
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url: 'https://www.npmjs.com/package/@rushstack/eslint-plugin'
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}
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},
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create: (context: TSESLint.RuleContext<MessageIds, Options>) => {

‎stack/eslint-plugin/src/no-untyped-underscore.ts‎

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},
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schema: [ ],
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docs: {
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description: 'Prevents usage of JavaScript\'s "null" keyword.',
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description: 'Prevent TypeScript code from accessing legacy JavaScript members'
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+ ' whose name has an underscore prefix',
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category: 'Stylistic Issues',
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recommended: "error",
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url: 'https://www.npmjs.com/package/@rushstack/eslint-config'
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recommended: false,
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url: 'https://www.npmjs.com/package/@rushstack/eslint-plugin'
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}
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},
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create: (context: TSESLint.RuleContext<MessageIds, Options>) => {

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