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feat(eslint-plugin): added new rule prefer-readonly (#555)
* feat(eslint-plugin): added new rule prefer-readonly Adds the equivalent of TSLint's `prefer-readonly` rule. * Added docs, auto-fixing * Updated docs; love the new build time checks! * Fixed linting errors (ha) and corrected internal source * PR feedback: non recommended; :exit; some test coverage * I guess tslintRuleName isn't allowed now? * Added back recommended as false * Removed :exit; fixed README.md table
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‎packages/eslint-plugin-tslint/src/custom-linter.ts

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@@ -4,7 +4,7 @@ import { Program } from 'typescript';
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const TSLintLinter = Linter as any;
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export class CustomLinter extends TSLintLinter {
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constructor(options: ILinterOptions, private program: Program) {
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constructor(options: ILinterOptions, private readonly program: Program) {
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super(options, program);
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}
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‎packages/eslint-plugin/README.md

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@@ -171,6 +171,7 @@ Then you should add `airbnb` (or `airbnb-base`) to your `extends` section of `.e
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| [`@typescript-eslint/prefer-function-type`](./docs/rules/prefer-function-type.md) | Use function types instead of interfaces with call signatures | | :wrench: | |
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| [`@typescript-eslint/prefer-includes`](./docs/rules/prefer-includes.md) | Enforce `includes` method over `indexOf` method | | :wrench: | :thought_balloon: |
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| [`@typescript-eslint/prefer-namespace-keyword`](./docs/rules/prefer-namespace-keyword.md) | Require the use of the `namespace` keyword instead of the `module` keyword to declare custom TypeScript modules | :heavy_check_mark: | :wrench: | |
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| [`@typescript-eslint/prefer-readonly`](./docs/rules/prefer-readonly.md) | Requires that private members are marked as `readonly` if they're never modified outside of the constructor | | :wrench: | :thought_balloon: |
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| [`@typescript-eslint/prefer-regexp-exec`](./docs/rules/prefer-regexp-exec.md) | Prefer RegExp#exec() over String#match() if no global flag is provided | | | :thought_balloon: |
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| [`@typescript-eslint/prefer-string-starts-ends-with`](./docs/rules/prefer-string-starts-ends-with.md) | Enforce the use of `String#startsWith` and `String#endsWith` instead of other equivalent methods of checking substrings | | :wrench: | :thought_balloon: |
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| [`@typescript-eslint/promise-function-async`](./docs/rules/promise-function-async.md) | Requires any function or method that returns a Promise to be marked async | | | :thought_balloon: |

‎packages/eslint-plugin/ROADMAP.md

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| [`no-require-imports`] | ✅ | [`@typescript-eslint/no-require-imports`] |
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| [`object-literal-sort-keys`] | 🌓 | [`sort-keys`][sort-keys] <sup>[2]</sup> |
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| [`prefer-const`] | 🌟 | [`prefer-const`][prefer-const] |
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| [`prefer-readonly`] | 🛑 | N/A |
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| [`prefer-readonly`] | ✅ | [`@typescript-eslint/prefer-readonly`] |
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| [`trailing-comma`] | 🌓 | [`comma-dangle`][comma-dangle] or [Prettier] |
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<sup>[1]</sup> Only warns when importing deprecated symbols<br>
@@ -611,6 +611,7 @@ Relevant plugins: [`chai-expect-keywords`](https://github.com/gavinaiken/eslint-
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[`@typescript-eslint/prefer-interface`]: https://github.com/typescript-eslint/typescript-eslint/blob/master/packages/eslint-plugin/docs/rules/prefer-interface.md
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[`@typescript-eslint/no-array-constructor`]: https://github.com/typescript-eslint/typescript-eslint/blob/master/packages/eslint-plugin/docs/rules/no-array-constructor.md
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[`@typescript-eslint/prefer-function-type`]: https://github.com/typescript-eslint/typescript-eslint/blob/master/packages/eslint-plugin/docs/rules/prefer-function-type.md
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[`@typescript-eslint/prefer-readonly`]: https://github.com/typescript-eslint/typescript-eslint/blob/master/packages/eslint-plugin/docs/rules/prefer-readonly.md
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[`@typescript-eslint/no-for-in-array`]: https://github.com/typescript-eslint/typescript-eslint/blob/master/packages/eslint-plugin/docs/rules/no-for-in-array.md
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[`@typescript-eslint/no-unnecessary-qualifier`]: https://github.com/typescript-eslint/typescript-eslint/blob/master/packages/eslint-plugin/docs/rules/no-unnecessary-qualifier.md
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[`@typescript-eslint/semi`]: https://github.com/typescript-eslint/typescript-eslint/blob/master/packages/eslint-plugin/docs/rules/semi.md

‎packages/eslint-plugin/docs/rules/prefer-readonly.md

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# require never-modified private members be marked as `readonly`
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This rule enforces that private members are marked as `readonly` if they're never modified outside of the constructor.
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## Rule Details
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Member variables with the privacy `private` are never permitted to be modified outside of their declaring class.
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If that class never modifies their value, they may safely be marked as `readonly`.
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Examples of **incorrect** code for this rule:
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```ts
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class Container {
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// These member variables could be marked as readonly
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private neverModifiedMember = true;
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private onlyModifiedInConstructor: number;
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public constructor(
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onlyModifiedInConstructor: number,
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// Private parameter properties can also be marked as reaodnly
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private neverModifiedParameter: string,
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) {
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this.onlyModifiedInConstructor = onlyModifiedInConstructor;
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}
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}
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```
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Examples of **correct** code for this rule:
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```ts
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class Container {
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// Public members might be modified externally
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public publicMember: boolean;
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// Protected members might be modified by child classes
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protected protectedMember: number;
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// This is modified later on by the class
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private modifiedLater = 'unchanged';
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public mutate() {
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this.modifiedLater = 'mutated';
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}
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}
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```
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## Options
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This rule, in its default state, does not require any argument.
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### onlyInlineLambdas
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You may pass `"onlyInlineLambdas": true` as a rule option within an object to restrict checking only to members immediately assigned a lambda value.
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```cjson
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{
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"@typescript-eslint/prefer-readonly": ["error", { "onlyInlineLambdas": true }]
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}
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```
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Example of **correct** code for the `{ "onlyInlineLambdas": true }` options:
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```ts
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class Container {
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private neverModifiedPrivate = 'unchanged';
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}
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```
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Example of **incorrect** code for the `{ "onlyInlineLambdas": true }` options:
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```ts
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class Container {
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private onClick = () => {
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/* ... */
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};
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}
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```
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## Related to
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- TSLint: ['prefer-readonly'](https://palantir.github.io/tslint/rules/prefer-readonly)

‎packages/eslint-plugin/src/configs/all.json

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"@typescript-eslint/prefer-function-type": "error",
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"@typescript-eslint/prefer-includes": "error",
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"@typescript-eslint/prefer-namespace-keyword": "error",
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"@typescript-eslint/prefer-readonly": "error",
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"@typescript-eslint/prefer-regexp-exec": "error",
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"@typescript-eslint/prefer-string-starts-ends-with": "error",
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"@typescript-eslint/promise-function-async": "error",

‎packages/eslint-plugin/src/rules/indent-new-do-not-use/OffsetStorage.ts

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* A class to store information on desired offsets of tokens from each other
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*/
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export class OffsetStorage {
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private tokenInfo: TokenInfo;
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private indentSize: number;
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private indentType: string;
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private tree: BinarySearchTree;
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private lockedFirstTokens: WeakMap<TokenOrComment, TokenOrComment>;
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private desiredIndentCache: WeakMap<TokenOrComment, string>;
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private ignoredTokens: WeakSet<TokenOrComment>;
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private readonly tokenInfo: TokenInfo;
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private readonly indentSize: number;
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private readonly indentType: string;
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private readonly tree: BinarySearchTree;
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private readonly lockedFirstTokens: WeakMap<TokenOrComment, TokenOrComment>;
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private readonly desiredIndentCache: WeakMap<TokenOrComment, string>;
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private readonly ignoredTokens: WeakSet<TokenOrComment>;
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/**
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* @param tokenInfo a TokenInfo instance
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* @param indentSize The desired size of each indentation level

‎packages/eslint-plugin/src/rules/indent-new-do-not-use/TokenInfo.ts

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* A helper class to get token-based info related to indentation
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*/
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export class TokenInfo {
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private sourceCode: TSESLint.SourceCode;
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private readonly sourceCode: TSESLint.SourceCode;
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public firstTokensByLineNumber: Map<number, TSESTree.Token>;
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constructor(sourceCode: TSESLint.SourceCode) {

‎packages/eslint-plugin/src/rules/index.ts

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import preferIncludes from './prefer-includes';
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import preferInterface from './prefer-interface';
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import preferNamespaceKeyword from './prefer-namespace-keyword';
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import preferReadonly from './prefer-readonly';
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import preferRegexpExec from './prefer-regexp-exec';
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import preferStringStartsEndsWith from './prefer-string-starts-ends-with';
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import promiseFunctionAsync from './promise-function-async';
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'prefer-includes': preferIncludes,
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'prefer-interface': preferInterface,
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'prefer-namespace-keyword': preferNamespaceKeyword,
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'prefer-readonly': preferReadonly,
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'prefer-regexp-exec': preferRegexpExec,
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'prefer-string-starts-ends-with': preferStringStartsEndsWith,
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'promise-function-async': promiseFunctionAsync,

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