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- const getLocation = (node) => ({
- end: node.params[node.params.length - 1].loc.end,
- start: node.params[0].loc.start,
- });
- const isOpeningParenToken = (token) => token.value === '(' && token.type === 'Punctuator';
- const isClosingParenToken = (token) => token.value === ')' && token.type === 'Punctuator';
- export default {
- create(context) {
- const asNeeded = context.options[0] === 'as-needed';
- const requireForBlockBody = (
- asNeeded
- && context.options[1] && context.options[1].requireForBlockBody === true
- );
- const sourceCode = context.getSourceCode();
- // Determines whether a arrow function argument end with `)`
- // eslint-disable-next-line complexity
- const parens = (node) => {
- const isAsync = node.async;
- const firstTokenOfParam = sourceCode.getFirstToken(node, isAsync ? 1 : 0);
- // Remove the parenthesis around a parameter
- const fixParamsWithParenthesis = (fixer) => {
- const paramToken = sourceCode.getTokenAfter(firstTokenOfParam);
- /*
- * ES8 allows Trailing commas in function parameter lists and calls
- * https://github.com/eslint/eslint/issues/8834
- */
- const closingParenToken = sourceCode.getTokenAfter(paramToken, isClosingParenToken);
- const asyncToken = isAsync ? sourceCode.getTokenBefore(firstTokenOfParam) : null;
- const shouldAddSpaceForAsync = (
- asyncToken
- && asyncToken.range[1] === firstTokenOfParam.range[0]
- );
- return fixer.replaceTextRange([
- firstTokenOfParam.range[0],
- closingParenToken.range[1],
- ], `${shouldAddSpaceForAsync ? ' ' : ''}${paramToken.value}`);
- };
- // Type parameters without an opening paren is always a parse error, and
- // can therefore be safely ignored.
- if (node.typeParameters) {
- return;
- }
- // Similarly, a predicate always requires parens just like a return type
- // does, and therefore this case can also be safely ignored.
- if (node.predicate) {
- return;
- }
- // "as-needed", { "requireForBlockBody": true }: x => x
- if (
- requireForBlockBody
- && node.params.length === 1
- && node.params[0].type === 'Identifier'
- && !node.params[0].typeAnnotation
- && node.body.type !== 'BlockStatement'
- && !node.returnType
- ) {
- if (isOpeningParenToken(firstTokenOfParam)) {
- context.report({
- fix: fixParamsWithParenthesis,
- loc: getLocation(node),
- messageId: 'unexpectedParensInline',
- node,
- });
- }
- return;
- }
- if (
- requireForBlockBody
- && node.body.type === 'BlockStatement'
- ) {
- if (!isOpeningParenToken(firstTokenOfParam)) {
- context.report({
- fix(fixer) {
- return fixer.replaceText(firstTokenOfParam, `(${firstTokenOfParam.value})`);
- },
- loc: getLocation(node),
- messageId: 'expectedParensBlock',
- node,
- });
- }
- return;
- }
- // "as-needed": x => x
- if (asNeeded
- && node.params.length === 1
- && node.params[0].type === 'Identifier'
- && !node.params[0].typeAnnotation
- && !node.returnType
- ) {
- if (isOpeningParenToken(firstTokenOfParam)) {
- context.report({
- fix: fixParamsWithParenthesis,
- loc: getLocation(node),
- messageId: 'unexpectedParens',
- node,
- });
- }
- return;
- }
- if (firstTokenOfParam.type === 'Identifier') {
- const after = sourceCode.getTokenAfter(firstTokenOfParam);
- // (x) => x
- if (after.value !== ')') {
- context.report({
- fix(fixer) {
- return fixer.replaceText(firstTokenOfParam, `(${firstTokenOfParam.value})`);
- },
- loc: getLocation(node),
- messageId: 'expectedParens',
- node,
- });
- }
- }
- };
- return {
- ArrowFunctionExpression: parens,
- };
- },
- meta: {
- docs: {
- category: 'ECMAScript 6',
- description: 'require parentheses around arrow function arguments',
- recommended: false,
- url: 'https://eslint.org/docs/rules/arrow-parens',
- },
- fixable: 'code',
- messages: {
- expectedParens: 'Expected parentheses around arrow function argument.',
- expectedParensBlock: 'Expected parentheses around arrow function argument having a body with curly braces.',
- unexpectedParens: 'Unexpected parentheses around single function argument.',
- unexpectedParensInline: 'Unexpected parentheses around single function argument having a body with no curly braces.',
- },
- type: 'layout',
- },
- schema: [
- {
- enum: ['always', 'as-needed'],
- },
- {
- additionalProperties: false,
- properties: {
- requireForBlockBody: {
- default: false,
- type: 'boolean',
- },
- },
- type: 'object',
- },
- ],
- };
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