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app_vue/node_modules/eslint-plugin-vue/lib/rules/no-multiple-template-root.js

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+/**
+ * @fileoverview disallow adding multiple root nodes to the template
+ * @author Przemyslaw Falowski (@przemkow)
+ */
+'use strict'
+
+// ------------------------------------------------------------------------------
+// Requirements
+// ------------------------------------------------------------------------------
+
+const utils = require('../utils')
+
+// ------------------------------------------------------------------------------
+// Rule Definition
+// ------------------------------------------------------------------------------
+
+module.exports = {
+  meta: {
+    type: 'problem',
+    docs: {
+      description: 'disallow adding multiple root nodes to the template',
+      categories: ['essential'],
+      url: 'https://eslint.vuejs.org/rules/no-multiple-template-root.html'
+    },
+    fixable: null,
+    schema: []
+  },
+  /**
+   * @param {RuleContext} context - The rule context.
+   * @returns {RuleListener} AST event handlers.
+   */
+  create(context) {
+    const sourceCode = context.getSourceCode()
+
+    return {
+      Program(program) {
+        const element = program.templateBody
+        if (element == null) {
+          return
+        }
+
+        const rootElements = []
+        let extraText = null
+        let extraElement = null
+        let vIf = false
+        for (const child of element.children) {
+          if (child.type === 'VElement') {
+            if (rootElements.length === 0) {
+              rootElements.push(child)
+              vIf = utils.hasDirective(child, 'if')
+            } else if (vIf && utils.hasDirective(child, 'else-if')) {
+              rootElements.push(child)
+            } else if (vIf && utils.hasDirective(child, 'else')) {
+              rootElements.push(child)
+              vIf = false
+            } else {
+              extraElement = child
+            }
+          } else if (sourceCode.getText(child).trim() !== '') {
+            extraText = child
+          }
+        }
+
+        if (extraText != null) {
+          context.report({
+            node: extraText,
+            loc: extraText.loc,
+            message: 'The template root requires an element rather than texts.'
+          })
+        } else if (extraElement != null) {
+          context.report({
+            node: extraElement,
+            loc: extraElement.loc,
+            message: 'The template root requires exactly one element.'
+          })
+        } else {
+          for (const element of rootElements) {
+            const tag = element.startTag
+            const name = element.name
+
+            if (name === 'template' || name === 'slot') {
+              context.report({
+                node: tag,
+                loc: tag.loc,
+                message: "The template root disallows '<{{name}}>' elements.",
+                data: { name }
+              })
+            }
+            if (utils.hasDirective(element, 'for')) {
+              context.report({
+                node: tag,
+                loc: tag.loc,
+                message: "The template root disallows 'v-for' directives."
+              })
+            }
+          }
+        }
+      }
+    }
+  }
+}