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app_vue/node_modules/eslint-plugin-vue/lib/rules/no-unused-vars.js

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+/**
+ * @fileoverview disallow unused variable definitions of v-for directives or scope attributes.
+ * @author 薛定谔的猫<hh_2013@foxmail.com>
+ */
+'use strict'
+
+const utils = require('../utils')
+
+/**
+ * @typedef {VVariable['kind']} VariableKind
+ */
+
+// ------------------------------------------------------------------------------
+// Helpers
+// ------------------------------------------------------------------------------
+
+/**
+ * Groups variables by directive kind.
+ * @param {VElement} node The element node
+ * @returns { { [kind in VariableKind]?: VVariable[] } } The variables of grouped by directive kind.
+ */
+function groupingVariables(node) {
+  /** @type { { [kind in VariableKind]?: VVariable[] } } */
+  const result = {}
+  for (const variable of node.variables) {
+    const vars = result[variable.kind] || (result[variable.kind] = [])
+    vars.push(variable)
+  }
+  return result
+}
+
+/**
+ * Checks if the given variable was defined by destructuring.
+ * @param {VVariable} variable the given variable to check
+ * @returns {boolean} `true` if the given variable was defined by destructuring.
+ */
+function isDestructuringVar(variable) {
+  const node = variable.id
+  /** @type {ASTNode | null} */
+  let parent = node.parent
+  while (parent) {
+    if (
+      parent.type === 'VForExpression' ||
+      parent.type === 'VSlotScopeExpression'
+    ) {
+      return false
+    }
+    if (parent.type === 'Property' || parent.type === 'ArrayPattern') {
+      return true
+    }
+    parent = parent.parent
+  }
+  return false
+}
+
+// ------------------------------------------------------------------------------
+// Rule Definition
+// ------------------------------------------------------------------------------
+
+module.exports = {
+  meta: {
+    hasSuggestions: true,
+    type: 'suggestion',
+    docs: {
+      description:
+        'disallow unused variable definitions of v-for directives or scope attributes',
+      categories: ['vue3-essential', 'essential'],
+      url: 'https://eslint.vuejs.org/rules/no-unused-vars.html'
+    },
+    fixable: null,
+    schema: [
+      {
+        type: 'object',
+        properties: {
+          ignorePattern: {
+            type: 'string'
+          }
+        },
+        additionalProperties: false
+      }
+    ]
+  },
+  /** @param {RuleContext} context */
+  create(context) {
+    const option = context.options[0] || {}
+    const ignorePattern = option.ignorePattern
+    /** @type {RegExp | null} */
+    let ignoreRegEx = null
+    if (ignorePattern) {
+      ignoreRegEx = new RegExp(ignorePattern, 'u')
+    }
+    return utils.defineTemplateBodyVisitor(context, {
+      /**
+       * @param {VElement} node
+       */
+      VElement(node) {
+        const vars = groupingVariables(node)
+        for (const variables of Object.values(vars)) {
+          if (!variables) {
+            continue
+          }
+          let hasAfterUsed = false
+
+          for (let i = variables.length - 1; i >= 0; i--) {
+            const variable = variables[i]
+
+            if (variable.references.length) {
+              hasAfterUsed = true
+              continue
+            }
+
+            if (ignoreRegEx != null && ignoreRegEx.test(variable.id.name)) {
+              continue
+            }
+
+            if (hasAfterUsed && !isDestructuringVar(variable)) {
+              // If a variable after the variable is used, it will be skipped.
+              continue
+            }
+
+            context.report({
+              node: variable.id,
+              loc: variable.id.loc,
+              message: `'{{name}}' is defined but never used.`,
+              data: {
+                name: variable.id.name
+              },
+              suggest:
+                ignorePattern === '^_'
+                  ? [
+                      {
+                        desc: `Replace the ${variable.id.name} with _${variable.id.name}`,
+                        fix(fixer) {
+                          return fixer.replaceText(
+                            variable.id,
+                            `_${variable.id.name}`
+                          )
+                        }
+                      }
+                    ]
+                  : []
+            })
+          }
+        }
+      }
+    })
+  }
+}