| import { defineRule } from '../utils/define-rule' |
| const url = 'https://nextjs.org/docs/messages/no-duplicate-head' |
|
|
| export = defineRule({ |
| meta: { |
| docs: { |
| description: |
| 'Prevent duplicate usage of `<Head>` in `pages/_document.js`.', |
| recommended: true, |
| url, |
| }, |
| type: 'problem', |
| schema: [], |
| }, |
| create(context) { |
| const { sourceCode } = context |
| let documentImportName |
| return { |
| ImportDeclaration(node) { |
| if (node.source.value === 'next/document') { |
| const documentImport = node.specifiers.find( |
| ({ type }) => type === 'ImportDefaultSpecifier' |
| ) |
| if (documentImport && documentImport.local) { |
| documentImportName = documentImport.local.name |
| } |
| } |
| }, |
| ReturnStatement(node) { |
| const ancestors = sourceCode.getAncestors(node) |
| const documentClass = ancestors.find( |
| (ancestorNode) => |
| ancestorNode.type === 'ClassDeclaration' && |
| ancestorNode.superClass && |
| 'name' in ancestorNode.superClass && |
| ancestorNode.superClass.name === documentImportName |
| ) |
|
|
| if (!documentClass) { |
| return |
| } |
|
|
| if ( |
| node.argument && |
| 'children' in node.argument && |
| node.argument.children |
| ) { |
| |
| const headComponents = node.argument.children.filter( |
| (childrenNode) => |
| childrenNode.openingElement && |
| childrenNode.openingElement.name && |
| childrenNode.openingElement.name.name === 'Head' |
| ) |
|
|
| if (headComponents.length > 1) { |
| for (let i = 1; i < headComponents.length; i++) { |
| context.report({ |
| node: headComponents[i], |
| message: `Do not include multiple instances of \`<Head/>\`. See: ${url}`, |
| }) |
| } |
| } |
| } |
| }, |
| } |
| }, |
| }) |
|
|
