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feat(eslint-plugin): add space-before-function-paren [extension] (#924)
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‎packages/eslint-plugin/README.md

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@@ -201,6 +201,7 @@ Then you should add `airbnb` (or `airbnb-base`) to your `extends` section of `.e
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| [`@typescript-eslint/require-await`](./docs/rules/require-await.md) | Disallow async functions which have no `await` expression | :heavy_check_mark: | | :thought_balloon: |
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| [`@typescript-eslint/restrict-plus-operands`](./docs/rules/restrict-plus-operands.md) | When adding two variables, operands must both be of type number or of type string | | | :thought_balloon: |
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| [`@typescript-eslint/semi`](./docs/rules/semi.md) | Require or disallow semicolons instead of ASI | | :wrench: | |
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| [`@typescript-eslint/space-before-function-paren`](./docs/rules/space-before-function-paren.md) | enforce consistent spacing before `function` definition opening parenthesis | | :wrench: | |
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| [`@typescript-eslint/strict-boolean-expressions`](./docs/rules/strict-boolean-expressions.md) | Restricts the types allowed in boolean expressions | | | :thought_balloon: |
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| [`@typescript-eslint/triple-slash-reference`](./docs/rules/triple-slash-reference.md) | Sets preference level for triple slash directives versus ES6-style import declarations | :heavy_check_mark: | | |
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| [`@typescript-eslint/type-annotation-spacing`](./docs/rules/type-annotation-spacing.md) | Require consistent spacing around type annotations | :heavy_check_mark: | :wrench: | |

‎packages/eslint-plugin/docs/rules/space-before-function-paren.md

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# Require or disallow a space before function parenthesis (space-before-function-paren)
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When formatting a function, whitespace is allowed between the function name or `function` keyword and the opening paren. Named functions also require a space between the `function` keyword and the function name, but anonymous functions require no whitespace. For example:
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<!-- prettier-ignore -->
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```ts
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function withoutSpace (x) {
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// ...
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}
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function withSpace (x) {
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// ...
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}
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var anonymousWithoutSpace = function () {};
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var anonymousWithSpace = function () {};
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```
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Style guides may require a space after the `function` keyword for anonymous functions, while others specify no whitespace. Similarly, the space after a function name may or may not be required.
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## Rule Details
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This rule extends the base [eslint/func-call-spacing](https://eslint.org/docs/rules/space-before-function-paren) rule.
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It supports all options and features of the base rule.
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This version adds support for generic type parameters on function calls.
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## How to use
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```cjson
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{
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// note you must disable the base rule as it can report incorrect errors
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"space-before-function-paren": "off",
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"@typescript-eslint/space-before-function-paren": ["error"]
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}
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```
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## Options
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See [eslint/space-before-function-paren options](https://eslint.org/docs/rules/space-before-function-paren#options).
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<sup>Taken with ❤️ [from ESLint core](https://github.com/eslint/eslint/blob/master/docs/rules/space-before-function-paren.md)</sup>

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

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"@typescript-eslint/restrict-plus-operands": "error",
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"semi": "off",
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"@typescript-eslint/semi": "error",
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"space-before-function-paren": "off",
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"@typescript-eslint/space-before-function-paren": "error",
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"@typescript-eslint/strict-boolean-expressions": "error",
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"@typescript-eslint/triple-slash-reference": "error",
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"@typescript-eslint/type-annotation-spacing": "error",

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

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import requireAwait from './require-await';
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import restrictPlusOperands from './restrict-plus-operands';
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import semi from './semi';
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import spaceBeforeFunctionParen from './space-before-function-paren';
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import strictBooleanExpressions from './strict-boolean-expressions';
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import tripleSlashReference from './triple-slash-reference';
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import typeAnnotationSpacing from './type-annotation-spacing';
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'require-await': requireAwait,
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'restrict-plus-operands': restrictPlusOperands,
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semi: semi,
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'space-before-function-paren': spaceBeforeFunctionParen,
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'strict-boolean-expressions': strictBooleanExpressions,
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'triple-slash-reference': tripleSlashReference,
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'type-annotation-spacing': typeAnnotationSpacing,

‎packages/eslint-plugin/src/rules/space-before-function-paren.ts

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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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import { isOpeningParenToken } from 'eslint-utils';
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import * as util from '../util';
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type Option = 'never' | 'always';
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type FuncOption = Option | 'ignore';
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export type Options = [
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| Option
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| Partial<{
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anonymous: FuncOption;
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named: FuncOption;
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asyncArrow: FuncOption;
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}>,
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];
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export type MessageIds = 'unexpected' | 'missing';
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export default util.createRule<Options, MessageIds>({
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name: 'space-before-function-paren',
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meta: {
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type: 'layout',
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docs: {
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description:
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'enforce consistent spacing before `function` definition opening parenthesis',
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category: 'Stylistic Issues',
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recommended: false,
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},
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fixable: 'whitespace',
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schema: [
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{
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oneOf: [
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{
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enum: ['always', 'never'],
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},
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{
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type: 'object',
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properties: {
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anonymous: {
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enum: ['always', 'never', 'ignore'],
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},
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named: {
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enum: ['always', 'never', 'ignore'],
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},
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asyncArrow: {
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enum: ['always', 'never', 'ignore'],
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},
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},
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additionalProperties: false,
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},
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],
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},
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],
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messages: {
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unexpected: 'Unexpected space before function parentheses.',
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missing: 'Missing space before function parentheses.',
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},
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},
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defaultOptions: ['always'],
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create(context) {
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const sourceCode = context.getSourceCode();
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const baseConfig =
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typeof context.options[0] === 'string' ? context.options[0] : 'always';
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const overrideConfig =
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typeof context.options[0] === 'object' ? context.options[0] : {};
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/**
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* Determines whether a function has a name.
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* @param {ASTNode} node The function node.
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* @returns {boolean} Whether the function has a name.
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*/
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function isNamedFunction(
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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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): boolean {
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if (node.id) {
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return true;
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}
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const parent = node.parent!;
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return (
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parent.type === 'MethodDefinition' ||
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(parent.type === 'Property' &&
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(parent.kind === 'get' || parent.kind === 'set' || parent.method))
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);
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}
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/**
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* Gets the config for a given function
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* @param {ASTNode} node The function node
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* @returns {string} "always", "never", or "ignore"
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*/
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function getConfigForFunction(
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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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): FuncOption {
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if (node.type === AST_NODE_TYPES.ArrowFunctionExpression) {
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// Always ignore non-async functions and arrow functions without parens, e.g. async foo => bar
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if (
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node.async &&
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isOpeningParenToken(sourceCode.getFirstToken(node, { skip: 1 })!)
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) {
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return overrideConfig.asyncArrow || baseConfig;
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}
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} else if (isNamedFunction(node)) {
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return overrideConfig.named || baseConfig;
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// `generator-star-spacing` should warn anonymous generators. E.g. `function* () {}`
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} else if (!node.generator) {
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return overrideConfig.anonymous || baseConfig;
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}
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return 'ignore';
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}
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/**
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* Checks the parens of a function node
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* @param {ASTNode} node A function node
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* @returns {void}
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*/
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function checkFunction(
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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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const functionConfig = getConfigForFunction(node);
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if (functionConfig === 'ignore') {
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return;
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}
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let leftToken: TSESTree.Token, rightToken: TSESTree.Token;
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if (node.typeParameters) {
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leftToken = sourceCode.getLastToken(node.typeParameters)!;
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rightToken = sourceCode.getTokenAfter(leftToken)!;
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} else {
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rightToken = sourceCode.getFirstToken(node, isOpeningParenToken)!;
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leftToken = sourceCode.getTokenBefore(rightToken)!;
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}
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const hasSpacing = sourceCode.isSpaceBetweenTokens(leftToken, rightToken);
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if (hasSpacing && functionConfig === 'never') {
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context.report({
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node,
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loc: leftToken.loc.end,
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messageId: 'unexpected',
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fix: fixer =>
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fixer.removeRange([leftToken.range[1], rightToken.range[0]]),
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});
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} else if (
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!hasSpacing &&
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functionConfig === 'always' &&
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(!node.typeParameters || node.id)
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) {
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context.report({
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node,
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loc: leftToken.loc.end,
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messageId: 'missing',
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fix: fixer => fixer.insertTextAfter(leftToken, ' '),
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});
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}
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}
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return {
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ArrowFunctionExpression: checkFunction,
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FunctionDeclaration: checkFunction,
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FunctionExpression: checkFunction,
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};
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},
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});

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