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