8000 feat(eslint-plugin): add default-param-last rule (#1418) · alex-dow/typescript-eslint@a37ff9f · GitHub
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feat(eslint-plugin): add default-param-last rule (typescript-eslint#1418)
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‎packages/eslint-plugin/README.md

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@@ -105,6 +105,7 @@ Pro Tip: For larger codebases you may want to consider splitting our linting int
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| [`@typescript-eslint/class-name-casing`](./docs/rules/class-name-casing.md) | Require PascalCased class and interface names | :heavy_check_mark: | | |
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| [`@typescript-eslint/consistent-type-assertions`](./docs/rules/consistent-type-assertions.md) | Enforces consistent usage of type assertions | :heavy_check_mark: | | |
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| [`@typescript-eslint/consistent-type-definitions`](./docs/rules/consistent-type-definitions.md) | Consistent with type definition either `interface` or `type` | | :wrench: | |
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| [`@typescript-eslint/default-param-last`](./docs/rules/default-param-last.md) | Enforce default parameters to be last | | | |
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| [`@typescript-eslint/explicit-function-return-type`](./docs/rules/explicit-function-return-type.md) | Require explicit return types on functions and class methods | :heavy_check_mark: | | |
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| [`@typescript-eslint/explicit-member-accessibility`](./docs/rules/explicit-member-accessibility.md) | Require explicit accessibility modifiers on class properties and methods | | | |
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| [`@typescript-eslint/func-call-spacing`](./docs/rules/func-call-spacing.md) | Require or disallow spacing between function identifiers and their invocations | | :wrench: | |

‎packages/eslint-plugin/docs/rules/default-param-last.md

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# Enforce default parameters to be last (`default-param-last`)
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## Rule Details
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This rule enforces default or optional parameters to be the last of parameters.
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Examples of **incorrect** code for this rule:
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```ts
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/* eslint @typescript-eslint/default-param-last: ["error"] */
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function f(a = 0, b: number) {}
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function f(a: number, b = 0, c?: number) {}
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function f(a: number, b = 0, c: number) {}
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function f(a: number, b?: number, c: number) {}
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```
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Examples of **correct** code for this rule:
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```ts
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/* eslint @typescript-eslint/default-param-last: ["error"] */
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function f(a = 0) {}
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function f(a: number, b = 0) {}
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function f(a: number, b?: number) {}
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function f(a: number, b?: number, c = 0) {}
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```
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<sup>Taken with ❤️ [from ESLint core](https://github.com/eslint/eslint/blob/master/docs/rules/default-param-last.md)</sup>

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

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"@typescript-eslint/class-name-casing": "error",
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"@typescript-eslint/consistent-type-assertions": "error",
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"@typescript-eslint/consistent-type-definitions": "error",
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"@typescript-eslint/default-param-last": "error",
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"@typescript-eslint/explicit-function-return-type": "error",
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"@typescript-eslint/explicit-member-accessibility": "error",
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"func-call-spacing": "off",

‎packages/eslint-plugin/src/rules/default-param-last.ts

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import { createRule } from '../util';
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import {
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TSESTree,
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AST_NODE_TYPES,
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} from '@typescript-eslint/experimental-utils';
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export default createRule({
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name: 'default-param-last',
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meta: {
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type: 'suggestion',
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docs: {
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description: 'Enforce default parameters to be last',
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category: 'Best Practices',
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recommended: false,
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},
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schema: [],
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messages: {
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shouldBeLast: 'Default parameters should be last.',
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},
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},
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defaultOptions: [],
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create(context) {
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/**
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* checks if node is optional parameter
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* @param node the node to be evaluated
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* @private
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*/
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function isOptionalParam(node: TSESTree.Parameter): boolean {
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return 'optional' in node && node.optional === true;
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}
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/**
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* checks if node is plain parameter
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* @param node the node to be evaluated
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* @private
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*/
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function isPlainParam(node: TSESTree.Parameter): boolean {
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return !(
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node.type === AST_NODE_TYPES.AssignmentPattern ||
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node.type === AST_NODE_TYPES.RestElement ||
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isOptionalParam(node)
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);
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}
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function checkDefaultParamLast(
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node:
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| TSESTree.ArrowFunctionExpression
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| TSESTree.FunctionDeclaration
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| TSESTree.FunctionExpression,
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): void {
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let hasSeenPlainParam = false;
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for (let i = node.params.length - 1; i >= 0; i--) {
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const param = node.params[i];
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if (isPlainParam(param)) {
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hasSeenPlainParam = true;
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continue;
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}
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if (
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hasSeenPlainParam &&
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(isOptionalParam(param) ||
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param.type === AST_NODE_TYPES.AssignmentPattern)
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) {
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context.report({ node: param, messageId: 'shouldBeLast' });
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}
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}
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}
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return {
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ArrowFunctionExpression: checkDefaultParamLast,
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FunctionDeclaration: checkDefaultParamLast,
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FunctionExpression: checkDefaultParamLast,
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};
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},
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});

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

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import classNameCasing from './class-name-casing';
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import consistentTypeAssertions from './consistent-type-assertions';
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import consistentTypeDefinitions from './consistent-type-definitions';
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import defaultParamLast from './default-param-last';
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import explicitFunctionReturnType from './explicit-function-return-type';
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import explicitMemberAccessibility from './explicit-member-accessibility';
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import funcCallSpacing from './func-call-spacing';
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'class-name-casing': classNameCasing,
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'consistent-type-assertions': consistentTypeAssertions,
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'consistent-type-definitions': consistentTypeDefinitions,
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'default-param-last': defaultParamLast,
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'explicit-function-return-type': explicitFunctionReturnType,
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'explicit-member-accessibility': explicitMemberAccessibility,
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'func-call-spacing': funcCallSpacing,

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