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 `` 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 ) { // @ts-expect-error - `node.argument` could be a `JSXElement` which has property `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 \`\`. See: ${url}`, }) } } } }, } }, })