Current File : /var/www/html/node_modules/eslint/lib/rules/class-methods-use-this.js
/**
* @fileoverview Rule to enforce that all class methods use 'this'.
* @author Patrick Williams
*/
"use strict";
//------------------------------------------------------------------------------
// Requirements
//------------------------------------------------------------------------------
const astUtils = require("./utils/ast-utils");
//------------------------------------------------------------------------------
// Rule Definition
//------------------------------------------------------------------------------
/** @type {import('../shared/types').Rule} */
module.exports = {
meta: {
type: "suggestion",
docs: {
description: "enforce that class methods utilize `this`",
recommended: false,
url: "https://eslint.org/docs/rules/class-methods-use-this"
},
schema: [{
type: "object",
properties: {
exceptMethods: {
type: "array",
items: {
type: "string"
}
},
enforceForClassFields: {
type: "boolean",
default: true
}
},
additionalProperties: false
}],
messages: {
missingThis: "Expected 'this' to be used by class {{name}}."
}
},
create(context) {
const config = Object.assign({}, context.options[0]);
const enforceForClassFields = config.enforceForClassFields !== false;
const exceptMethods = new Set(config.exceptMethods || []);
const stack = [];
/**
* Push `this` used flag initialized with `false` onto the stack.
* @returns {void}
*/
function pushContext() {
stack.push(false);
}
/**
* Pop `this` used flag from the stack.
* @returns {boolean | undefined} `this` used flag
*/
function popContext() {
return stack.pop();
}
/**
* 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() {
pushContext();
}
/**
* 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) {
switch (node.type) {
case "MethodDefinition":
return !node.static && node.kind !== "constructor";
case "PropertyDefinition":
return !node.static && enforceForClassFields;
default:
return false;
}
}
/**
* 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) {
if (isInstanceMethod(node)) {
if (node.computed) {
return true;
}
const hashIfNeeded = node.key.type === "PrivateIdentifier" ? "#" : "";
const name = node.key.type === "Literal"
? astUtils.getStaticStringValue(node.key)
: (node.key.name || "");
return !exceptMethods.has(hashIfNeeded + name);
}
return false;
}
/**
* 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 = popContext();
if (isIncludedInstanceMethod(node.parent) && !methodUsesThis) {
context.report({
node,
loc: astUtils.getFunctionHeadLoc(node, context.getSourceCode()),
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,
/*
* Class field value are implicit functions.
*/
"PropertyDefinition > *.key:exit": pushContext,
"PropertyDefinition:exit": popContext,
/*
* Class static blocks are implicit functions. They aren't required to use `this`,
* but we have to push context so that it captures any use of `this` in the static block
* separately from enclosing contexts, because static blocks have their own `this` and it
* shouldn't count as used `this` in enclosing contexts.
*/
StaticBlock: pushContext,
"StaticBlock:exit": popContext,
ThisExpression: markThisUsed,
Super: markThisUsed,
...(
enforceForClassFields && {
"PropertyDefinition > ArrowFunctionExpression.value": enterFunction,
"PropertyDefinition > ArrowFunctionExpression.value:exit": exitFunction
}
)
};
}
};
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