| /** |
| * @fileoverview Rule to enforce that all class methods use 'this'. |
| * @author Patrick Williams |
| */ |
| |
| "use strict"; |
| |
| //------------------------------------------------------------------------------ |
| // 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 method '{{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) && !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: node.parent.key.name |
| } |
| }); |
| } |
| } |
| |
| /** |
| * 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 |
| }; |
| } |
| }; |