311 lines
11 KiB
JavaScript
311 lines
11 KiB
JavaScript
|
/**
|
||
|
|
* @fileoverview A rule to suggest using arrow functions as callbacks.
|
||
|
|
* @author Toru Nagashima
|
||
|
|
*/
|
||
|
|
|
||
|
|
"use strict";
|
||
|
|
|
||
|
|
//------------------------------------------------------------------------------
|
||
|
|
// Helpers
|
||
|
|
//------------------------------------------------------------------------------
|
||
|
|
|
||
|
|
/**
|
||
|
|
* Checks whether or not a given variable is a function name.
|
||
|
|
* @param {eslint-scope.Variable} variable - A variable to check.
|
||
|
|
* @returns {boolean} `true` if the variable is a function name.
|
||
|
|
*/
|
||
|
|
function isFunctionName(variable) {
|
||
|
|
return variable && variable.defs[0].type === "FunctionName";
|
||
|
|
}
|
||
|
|
|
||
|
|
/**
|
||
|
|
* Checks whether or not a given MetaProperty node equals to a given value.
|
||
|
|
* @param {ASTNode} node - A MetaProperty node to check.
|
||
|
|
* @param {string} metaName - The name of `MetaProperty.meta`.
|
||
|
|
* @param {string} propertyName - The name of `MetaProperty.property`.
|
||
|
|
* @returns {boolean} `true` if the node is the specific value.
|
||
|
|
*/
|
||
|
|
function checkMetaProperty(node, metaName, propertyName) {
|
||
|
|
return node.meta.name === metaName && node.property.name === propertyName;
|
||
|
|
}
|
||
|
|
|
||
|
|
/**
|
||
|
|
* Gets the variable object of `arguments` which is defined implicitly.
|
||
|
|
* @param {eslint-scope.Scope} scope - A scope to get.
|
||
|
|
* @returns {eslint-scope.Variable} The found variable object.
|
||
|
|
*/
|
||
|
|
function getVariableOfArguments(scope) {
|
||
|
|
const variables = scope.variables;
|
||
|
|
|
||
|
|
for (let i = 0; i < variables.length; ++i) {
|
||
|
|
const variable = variables[i];
|
||
|
|
|
||
|
|
if (variable.name === "arguments") {
|
||
|
|
|
||
|
|
/*
|
||
|
|
* If there was a parameter which is named "arguments", the
|
||
|
|
* implicit "arguments" is not defined.
|
||
|
|
* So does fast return with null.
|
||
|
|
*/
|
||
|
|
return (variable.identifiers.length === 0) ? variable : null;
|
||
|
|
}
|
||
|
|
}
|
||
|
|
|
||
|
|
/* istanbul ignore next */
|
||
|
|
return null;
|
||
|
|
}
|
||
|
|
|
||
|
|
/**
|
||
|
|
* Checkes whether or not a given node is a callback.
|
||
|
|
* @param {ASTNode} node - A node to check.
|
||
|
|
* @returns {Object}
|
||
|
|
* {boolean} retv.isCallback - `true` if the node is a callback.
|
||
|
|
* {boolean} retv.isLexicalThis - `true` if the node is with `.bind(this)`.
|
||
|
|
*/
|
||
|
|
function getCallbackInfo(node) {
|
||
|
|
const retv = { isCallback: false, isLexicalThis: false };
|
||
|
|
let currentNode = node;
|
||
|
|
let parent = node.parent;
|
||
|
|
|
||
|
|
while (currentNode) {
|
||
|
|
switch (parent.type) {
|
||
|
|
|
||
|
|
// Checks parents recursively.
|
||
|
|
|
||
|
|
case "LogicalExpression":
|
||
|
|
case "ConditionalExpression":
|
||
|
|
break;
|
||
|
|
|
||
|
|
// Checks whether the parent node is `.bind(this)` call.
|
||
|
|
case "MemberExpression":
|
||
|
|
if (parent.object === currentNode &&
|
||
|
|
!parent.property.computed &&
|
||
|
|
parent.property.type === "Identifier" &&
|
||
|
|
parent.property.name === "bind" &&
|
||
|
|
parent.parent.type === "CallExpression" &&
|
||
|
|
parent.parent.callee === parent
|
||
|
|
) {
|
||
|
|
retv.isLexicalThis = (
|
||
|
|
parent.parent.arguments.length === 1 &&
|
||
|
|
parent.parent.arguments[0].type === "ThisExpression"
|
||
|
|
);
|
||
|
|
parent = parent.parent;
|
||
|
|
} else {
|
||
|
|
return retv;
|
||
|
|
}
|
||
|
|
break;
|
||
|
|
|
||
|
|
// Checks whether the node is a callback.
|
||
|
|
case "CallExpression":
|
||
|
|
case "NewExpression":
|
||
|
|
if (parent.callee !== currentNode) {
|
||
|
|
retv.isCallback = true;
|
||
|
|
}
|
||
|
|
return retv;
|
||
|
|
|
||
|
|
default:
|
||
|
|
return retv;
|
||
|
|
}
|
||
|
|
|
||
|
|
currentNode = parent;
|
||
|
|
parent = parent.parent;
|
||
|
|
}
|
||
|
|
|
||
|
|
/* istanbul ignore next */
|
||
|
|
throw new Error("unreachable");
|
||
|
|
}
|
||
|
|
|
||
|
|
/**
|
||
|
|
* Checks whether a simple list of parameters contains any duplicates. This does not handle complex
|
||
|
|
* parameter lists (e.g. with destructuring), since complex parameter lists are a SyntaxError with duplicate
|
||
|
|
* parameter names anyway. Instead, it always returns `false` for complex parameter lists.
|
||
|
|
* @param {ASTNode[]} paramsList The list of parameters for a function
|
||
|
|
* @returns {boolean} `true` if the list of parameters contains any duplicates
|
||
|
|
*/
|
||
|
|
function hasDuplicateParams(paramsList) {
|
||
|
|
return paramsList.every(param => param.type === "Identifier") && paramsList.length !== new Set(paramsList.map(param => param.name)).size;
|
||
|
|
}
|
||
|
|
|
||
|
|
//------------------------------------------------------------------------------
|
||
|
|
// Rule Definition
|
||
|
|
//------------------------------------------------------------------------------
|
||
|
|
|
||
|
|
module.exports = {
|
||
|
|
meta: {
|
||
|
|
type: "suggestion",
|
||
|
|
|
||
|
|
docs: {
|
||
|
|
description: "require using arrow functions for callbacks",
|
||
|
|
category: "ECMAScript 6",
|
||
|
|
recommended: false,
|
||
|
|
url: "https://eslint.org/docs/rules/prefer-arrow-callback"
|
||
|
|
},
|
||
|
|
|
||
|
|
schema: [
|
||
|
|
{
|
||
|
|
type: "object",
|
||
|
|
properties: {
|
||
|
|
allowNamedFunctions: {
|
||
|
|
type: "boolean",
|
||
|
|
default: false
|
||
|
|
},
|
||
|
|
allowUnboundThis: {
|
||
|
|
type: "boolean",
|
||
|
|
default: true
|
||
|
|
}
|
||
|
|
},
|
||
|
|
additionalProperties: false
|
||
|
|
}
|
||
|
|
],
|
||
|
|
|
||
|
|
fixable: "code"
|
||
|
|
},
|
||
|
|
|
||
|
|
create(context) {
|
||
|
|
const options = context.options[0] || {};
|
||
|
|
|
||
|
|
const allowUnboundThis = options.allowUnboundThis !== false; // default to true
|
||
|
|
const allowNamedFunctions = options.allowNamedFunctions;
|
||
|
|
const sourceCode = context.getSourceCode();
|
||
|
|
|
||
|
|
/*
|
||
|
|
* {Array<{this: boolean, super: boolean, meta: boolean}>}
|
||
|
|
* - this - A flag which shows there are one or more ThisExpression.
|
||
|
|
* - super - A flag which shows there are one or more Super.
|
||
|
|
* - meta - A flag which shows there are one or more MethProperty.
|
||
|
|
*/
|
||
|
|
let stack = [];
|
||
|
|
|
||
|
|
/**
|
||
|
|
* Pushes new function scope with all `false` flags.
|
||
|
|
* @returns {void}
|
||
|
|
*/
|
||
|
|
function enterScope() {
|
||
|
|
stack.push({ this: false, super: false, meta: false });
|
||
|
|
}
|
||
|
|
|
||
|
|
/**
|
||
|
|
* Pops a function scope from the stack.
|
||
|
|
* @returns {{this: boolean, super: boolean, meta: boolean}} The information of the last scope.
|
||
|
|
*/
|
||
|
|
function exitScope() {
|
||
|
|
return stack.pop();
|
||
|
|
}
|
||
|
|
|
||
|
|
return {
|
||
|
|
|
||
|
|
// Reset internal state.
|
||
|
|
Program() {
|
||
|
|
stack = [];
|
||
|
|
},
|
||
|
|
|
||
|
|
// If there are below, it cannot replace with arrow functions merely.
|
||
|
|
ThisExpression() {
|
||
|
|
const info = stack[stack.length - 1];
|
||
|
|
|
||
|
|
if (info) {
|
||
|
|
info.this = true;
|
||
|
|
}
|
||
|
|
},
|
||
|
|
|
||
|
|
Super() {
|
||
|
|
const info = stack[stack.length - 1];
|
||
|
|
|
||
|
|
if (info) {
|
||
|
|
info.super = true;
|
||
|
|
}
|
||
|
|
},
|
||
|
|
|
||
|
|
MetaProperty(node) {
|
||
|
|
const info = stack[stack.length - 1];
|
||
|
|
|
||
|
|
if (info && checkMetaProperty(node, "new", "target")) {
|
||
|
|
info.meta = true;
|
||
|
|
}
|
||
|
|
},
|
||
|
|
|
||
|
|
// To skip nested scopes.
|
||
|
|
FunctionDeclaration: enterScope,
|
||
|
|
"FunctionDeclaration:exit": exitScope,
|
||
|
|
|
||
|
|
// Main.
|
||
|
|
FunctionExpression: enterScope,
|
||
|
|
"FunctionExpression:exit"(node) {
|
||
|
|
const scopeInfo = exitScope();
|
||
|
|
|
||
|
|
// Skip named function expressions
|
||
|
|
if (allowNamedFunctions && node.id && node.id.name) {
|
||
|
|
return;
|
||
|
|
}
|
||
|
|
|
||
|
|
// Skip generators.
|
||
|
|
if (node.generator) {
|
||
|
|
return;
|
||
|
|
}
|
||
|
|
|
||
|
|
// Skip recursive functions.
|
||
|
|
const nameVar = context.getDeclaredVariables(node)[0];
|
||
|
|
|
||
|
|
if (isFunctionName(nameVar) && nameVar.references.length > 0) {
|
||
|
|
return;
|
||
|
|
}
|
||
|
|
|
||
|
|
// Skip if it's using arguments.
|
||
|
|
const variable = getVariableOfArguments(context.getScope());
|
||
|
|
|
||
|
|
if (variable && variable.references.length > 0) {
|
||
|
|
return;
|
||
|
|
}
|
||
|
|
|
||
|
|
// Reports if it's a callback which can replace with arrows.
|
||
|
|
const callbackInfo = getCallbackInfo(node);
|
||
|
|
|
||
|
|
if (callbackInfo.isCallback &&
|
||
|
|
(!allowUnboundThis || !scopeInfo.this || callbackInfo.isLexicalThis) &&
|
||
|
|
!scopeInfo.super &&
|
||
|
|
!scopeInfo.meta
|
||
|
|
) {
|
||
|
|
context.report({
|
||
|
|
node,
|
||
|
|
message: "Unexpected function expression.",
|
||
|
|
fix(fixer) {
|
||
|
|
if ((!callbackInfo.isLexicalThis && scopeInfo.this) || hasDuplicateParams(node.params)) {
|
||
|
|
|
||
|
|
/*
|
||
|
|
* If the callback function does not have .bind(this) and contains a reference to `this`, there
|
||
|
|
* is no way to determine what `this` should be, so don't perform any fixes.
|
||
|
|
* If the callback function has duplicates in its list of parameters (possible in sloppy mode),
|
||
|
|
* don't replace it with an arrow function, because this is a SyntaxError with arrow functions.
|
||
|
|
*/
|
||
|
|
return null;
|
||
|
|
}
|
||
|
|
|
||
|
|
const paramsLeftParen = node.params.length ? sourceCode.getTokenBefore(node.params[0]) : sourceCode.getTokenBefore(node.body, 1);
|
||
|
|
const paramsRightParen = sourceCode.getTokenBefore(node.body);
|
||
|
|
const asyncKeyword = node.async ? "async " : "";
|
||
|
|
const paramsFullText = sourceCode.text.slice(paramsLeftParen.range[0], paramsRightParen.range[1]);
|
||
|
|
const arrowFunctionText = `${asyncKeyword}${paramsFullText} => ${sourceCode.getText(node.body)}`;
|
||
|
|
|
||
|
|
/*
|
||
|
|
* If the callback function has `.bind(this)`, replace it with an arrow function and remove the binding.
|
||
|
|
* Otherwise, just replace the arrow function itself.
|
||
|
|
*/
|
||
|
|
const replacedNode = callbackInfo.isLexicalThis ? node.parent.parent : node;
|
||
|
|
|
||
|
|
/*
|
||
|
|
* If the replaced node is part of a BinaryExpression, LogicalExpression, or MemberExpression, then
|
||
|
|
* the arrow function needs to be parenthesized, because `foo || () => {}` is invalid syntax even
|
||
|
|
* though `foo || function() {}` is valid.
|
||
|
|
*/
|
||
|
|
const needsParens = replacedNode.parent.type !== "CallExpression" && replacedNode.parent.type !== "ConditionalExpression";
|
||
|
|
const replacementText = needsParens ? `(${arrowFunctionText})` : arrowFunctionText;
|
||
|
|
|
||
|
|
return fixer.replaceText(replacedNode, replacementText);
|
||
|
|
}
|
||
|
|
});
|
||
|
|
}
|
||
|
|
}
|
||
|
|
};
|
||
|
|
}
|
||
|
|
};
|