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/**
* @fileoverview Rule to disallow returning values from setters
* @author Milos Djermanovic
*/
"use strict";
//------------------------------------------------------------------------------
// Requirements
//------------------------------------------------------------------------------
const astUtils = require("./utils/ast-utils");
const { findVariable } = require("eslint-utils");
//------------------------------------------------------------------------------
// Helpers
//------------------------------------------------------------------------------
/**
* Determines whether the given identifier node is a reference to a global variable.
* @param {ASTNode} node `Identifier` node to check.
* @param {Scope} scope Scope to which the node belongs.
* @returns {boolean} True if the identifier is a reference to a global variable.
*/
function isGlobalReference(node, scope) {
const variable = findVariable(scope, node);
return variable !== null && variable.scope.type === "global" && variable.defs.length === 0;
}
/**
* Determines whether the given node is an argument of the specified global method call, at the given `index` position.
* E.g., for given `index === 1`, this function checks for `objectName.methodName(foo, node)`, where objectName is a global variable.
* @param {ASTNode} node The node to check.
* @param {Scope} scope Scope to which the node belongs.
* @param {string} objectName Name of the global object.
* @param {string} methodName Name of the method.
* @param {number} index The given position.
* @returns {boolean} `true` if the node is argument at the given position.
*/
function isArgumentOfGlobalMethodCall(node, scope, objectName, methodName, index) {
const parent = node.parent;
return parent.type === "CallExpression" &&
parent.arguments[index] === node &&
parent.callee.type === "MemberExpression" &&
astUtils.getStaticPropertyName(parent.callee) === methodName &&
parent.callee.object.type === "Identifier" &&
parent.callee.object.name === objectName &&
isGlobalReference(parent.callee.object, scope);
}
/**
* Determines whether the given node is used as a property descriptor.
* @param {ASTNode} node The node to check.
* @param {Scope} scope Scope to which the node belongs.
* @returns {boolean} `true` if the node is a property descriptor.
*/
function isPropertyDescriptor(node, scope) {
if (
isArgumentOfGlobalMethodCall(node, scope, "Object", "defineProperty", 2) ||
isArgumentOfGlobalMethodCall(node, scope, "Reflect", "defineProperty", 2)
) {
return true;
}
const parent = node.parent;
if (
parent.type === "Property" &&
parent.value === node
) {
const grandparent = parent.parent;
if (
grandparent.type === "ObjectExpression" &&
(
isArgumentOfGlobalMethodCall(grandparent, scope, "Object", "create", 1) ||
isArgumentOfGlobalMethodCall(grandparent, scope, "Object", "defineProperties", 1)
)
) {
return true;
}
}
return false;
}
/**
* Determines whether the given function node is used as a setter function.
* @param {ASTNode} node The node to check.
* @param {Scope} scope Scope to which the node belongs.
* @returns {boolean} `true` if the node is a setter.
*/
function isSetter(node, scope) {
const parent = node.parent;
if (
parent.kind === "set" &&
parent.value === node
) {
// Setter in an object literal or in a class
return true;
}
if (
parent.type === "Property" &&
parent.value === node &&
astUtils.getStaticPropertyName(parent) === "set" &&
parent.parent.type === "ObjectExpression" &&
isPropertyDescriptor(parent.parent, scope)
) {
// Setter in a property descriptor
return true;
}
return false;
}
/**
* Finds function's outer scope.
* @param {Scope} scope Function's own scope.
* @returns {Scope} Function's outer scope.
*/
function getOuterScope(scope) {
const upper = scope.upper;
if (upper.type === "function-expression-name") {
return upper.upper;
}
return upper;
}
//------------------------------------------------------------------------------
// Rule Definition
//------------------------------------------------------------------------------
module.exports = {
meta: {
type: "problem",
docs: {
description: "disallow returning values from setters",
category: "Possible Errors",
recommended: false,
url: "https://eslint.org/docs/rules/no-setter-return"
},
schema: [],
messages: {
returnsValue: "Setter cannot return a value."
}
},
create(context) {
let funcInfo = null;
/**
* Creates and pushes to the stack a function info object for the given function node.
* @param {ASTNode} node The function node.
* @returns {void}
*/
function enterFunction(node) {
const outerScope = getOuterScope(context.getScope());
funcInfo = {
upper: funcInfo,
isSetter: isSetter(node, outerScope)
};
}
/**
* Pops the current function info object from the stack.
* @returns {void}
*/
function exitFunction() {
funcInfo = funcInfo.upper;
}
/**
* Reports the given node.
* @param {ASTNode} node Node to report.
* @returns {void}
*/
function report(node) {
context.report({ node, messageId: "returnsValue" });
}
return {
/*
* Function declarations cannot be setters, but we still have to track them in the `funcInfo` stack to avoid
* false positives, because a ReturnStatement node can belong to a function declaration inside a setter.
*
* Note: A previously declared function can be referenced and actually used as a setter in a property descriptor,
* but that's out of scope for this rule.
*/
FunctionDeclaration: enterFunction,
FunctionExpression: enterFunction,
ArrowFunctionExpression(node) {
enterFunction(node);
if (funcInfo.isSetter && node.expression) {
// { set: foo => bar } property descriptor. Report implicit return 'bar' as the equivalent for a return statement.
report(node.body);
}
},
"FunctionDeclaration:exit": exitFunction,
"FunctionExpression:exit": exitFunction,
"ArrowFunctionExpression:exit": exitFunction,
ReturnStatement(node) {
// Global returns (e.g., at the top level of a Node module) don't have `funcInfo`.
if (funcInfo && funcInfo.isSetter && node.argument) {
report(node);
}
}
};
}
};
|
