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app_vue/node_modules/eslint/lib/rules/class-methods-use-this.js

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+/**
+ * @fileoverview Rule to enforce that all class methods use 'this'.
+ * @author Patrick Williams
+ */
+
+"use strict";
+
+//------------------------------------------------------------------------------
+// Requirements
+//------------------------------------------------------------------------------
+
+const astUtils = require("./utils/ast-utils");
+
+//------------------------------------------------------------------------------
+// Rule Definition
+//------------------------------------------------------------------------------
+
+module.exports = {
+    meta: {
+        type: "suggestion",
+
+        docs: {
+            description: "enforce that class methods utilize `this`",
+            category: "Best Practices",
+            recommended: false,
+            url: "https://eslint.org/docs/rules/class-methods-use-this"
+        },
+
+        schema: [{
+            type: "object",
+            properties: {
+                exceptMethods: {
+                    type: "array",
+                    items: {
+                        type: "string"
+                    }
+                }
+            },
+            additionalProperties: false
+        }],
+
+        messages: {
+            missingThis: "Expected 'this' to be used by class {{name}}."
+        }
+    },
+    create(context) {
+        const config = Object.assign({}, context.options[0]);
+        const exceptMethods = new Set(config.exceptMethods || []);
+
+        const stack = [];
+
+        /**
+         * Initializes the current context to false and pushes it onto the stack.
+         * These booleans represent whether 'this' has been used in the context.
+         * @returns {void}
+         * @private
+         */
+        function enterFunction() {
+            stack.push(false);
+        }
+
+        /**
+         * Check if the node is an instance method
+         * @param {ASTNode} node node to check
+         * @returns {boolean} True if its an instance method
+         * @private
+         */
+        function isInstanceMethod(node) {
+            return !node.static && node.kind !== "constructor" && node.type === "MethodDefinition";
+        }
+
+        /**
+         * Check if the node is an instance method not excluded by config
+         * @param {ASTNode} node node to check
+         * @returns {boolean} True if it is an instance method, and not excluded by config
+         * @private
+         */
+        function isIncludedInstanceMethod(node) {
+            return isInstanceMethod(node) &&
+                (node.computed || !exceptMethods.has(node.key.name));
+        }
+
+        /**
+         * Checks if we are leaving a function that is a method, and reports if 'this' has not been used.
+         * Static methods and the constructor are exempt.
+         * Then pops the context off the stack.
+         * @param {ASTNode} node A function node that was entered.
+         * @returns {void}
+         * @private
+         */
+        function exitFunction(node) {
+            const methodUsesThis = stack.pop();
+
+            if (isIncludedInstanceMethod(node.parent) && !methodUsesThis) {
+                context.report({
+                    node,
+                    messageId: "missingThis",
+                    data: {
+                        name: astUtils.getFunctionNameWithKind(node)
+                    }
+                });
+            }
+        }
+
+        /**
+         * Mark the current context as having used 'this'.
+         * @returns {void}
+         * @private
+         */
+        function markThisUsed() {
+            if (stack.length) {
+                stack[stack.length - 1] = true;
+            }
+        }
+
+        return {
+            FunctionDeclaration: enterFunction,
+            "FunctionDeclaration:exit": exitFunction,
+            FunctionExpression: enterFunction,
+            "FunctionExpression:exit": exitFunction,
+            ThisExpression: markThisUsed,
+            Super: markThisUsed
+        };
+    }
+};