eslint/tests/lib/rules/prefer-arrow-callback.js

   1 /**
   2  * @fileoverview Tests for prefer-arrow-callback rule.
   3  * @author Toru Nagashima
   4  */
   5
   6 "use strict";
   7
   8 //------------------------------------------------------------------------------
   9 // Requirements
  10 //------------------------------------------------------------------------------
  11
  12 const rule = require("../../../lib/rules/prefer-arrow-callback");
  13 const { RuleTester } = require("../../../lib/rule-tester");
  14
  15 //------------------------------------------------------------------------------
  16 // Tests
  17 //------------------------------------------------------------------------------
  18
  19 const errors = [{
  20     messageId: "preferArrowCallback",
  21     type: "FunctionExpression"
  22 }];
  23
  24 const ruleTester = new RuleTester({ parserOptions: { ecmaVersion: 2020 } });
  25
  26 ruleTester.run("prefer-arrow-callback", rule, {
  27     valid: [
  28         "foo(a => a);",
  29         "foo(function*() {});",
  30         "foo(function() { this; });",
  31         { code: "foo(function bar() {});", options: [{ allowNamedFunctions: true }] },
  32         "foo(function() { (() => this); });",
  33         "foo(function() { this; }.bind(obj));",
  34         "foo(function() { this; }.call(this));",
  35         "foo(a => { (function() {}); });",
  36         "var foo = function foo() {};",
  37         "(function foo() {})();",
  38         "foo(function bar() { bar; });",
  39         "foo(function bar() { arguments; });",
  40         "foo(function bar() { arguments; }.bind(this));",
  41         "foo(function bar() { new.target; });",
  42         "foo(function bar() { new.target; }.bind(this));",
  43         "foo(function bar() { this; }.bind(this, somethingElse));",
  44         "foo((function() {}).bind.bar)",
  45         "foo((function() { this.bar(); }).bind(obj).bind(this))"
  46     ],
  47     invalid: [
  48         {
  49             code: "foo(function bar() {});",
  50             output: "foo(() => {});",
  51             errors
  52         },
  53         {
  54             code: "foo(function() {});",
  55             output: "foo(() => {});",
  56             options: [{ allowNamedFunctions: true }],
  57             errors
  58         },
  59         {
  60             code: "foo(function bar() {});",
  61             output: "foo(() => {});",
  62             options: [{ allowNamedFunctions: false }],
  63             errors
  64         },
  65         {
  66             code: "foo(function() {});",
  67             output: "foo(() => {});",
  68             errors
  69         },
  70         {
  71             code: "foo(nativeCb || function() {});",
  72             output: "foo(nativeCb || (() => {}));",
  73             errors
  74         },
  75         {
  76             code: "foo(bar ? function() {} : function() {});",
  77             output: "foo(bar ? () => {} : () => {});",
  78             errors: [errors[0], errors[0]]
  79         },
  80         {
  81             code: "foo(function() { (function() { this; }); });",
  82             output: "foo(() => { (function() { this; }); });",
  83             errors
  84         },
  85         {
  86             code: "foo(function() { this; }.bind(this));",
  87             output: "foo(() => { this; });",
  88             errors
  89         },
  90         {
  91             code: "foo(bar || function() { this; }.bind(this));",
  92             output: "foo(bar || (() => { this; }));",
  93             errors
  94         },
  95         {
  96             code: "foo(function() { (() => this); }.bind(this));",
  97             output: "foo(() => { (() => this); });",
  98             errors
  99         },
 100         {
 101             code: "foo(function bar(a) { a; });",
 102             output: "foo((a) => { a; });",
 103             errors
 104         },
 105         {
 106             code: "foo(function(a) { a; });",
 107             output: "foo((a) => { a; });",
 108             errors
 109         },
 110         {
 111             code: "foo(function(arguments) { arguments; });",
 112             output: "foo((arguments) => { arguments; });",
 113             errors
 114         },
 115         {
 116             code: "foo(function() { this; });",
 117             output: null, // No fix applied
 118             options: [{ allowUnboundThis: false }],
 119             errors
 120         },
 121         {
 122             code: "foo(function() { (() => this); });",
 123             output: null, // No fix applied
 124             options: [{ allowUnboundThis: false }],
 125             errors
 126         },
 127         {
 128             code: "qux(function(foo, bar, baz) { return foo * 2; })",
 129             output: "qux((foo, bar, baz) => { return foo * 2; })",
 130             errors
 131         },
 132         {
 133             code: "qux(function(foo, bar, baz) { return foo * bar; }.bind(this))",
 134             output: "qux((foo, bar, baz) => { return foo * bar; })",
 135             errors
 136         },
 137         {
 138             code: "qux(function(foo, bar, baz) { return foo * this.qux; }.bind(this))",
 139             output: "qux((foo, bar, baz) => { return foo * this.qux; })",
 140             errors
 141         },
 142         {
 143             code: "foo(function() {}.bind(this, somethingElse))",
 144             output: "foo((() => {}).bind(this, somethingElse))",
 145             errors
 146         },
 147         {
 148             code: "qux(function(foo = 1, [bar = 2] = [], {qux: baz = 3} = {foo: 'bar'}) { return foo + bar; });",
 149             output: "qux((foo = 1, [bar = 2] = [], {qux: baz = 3} = {foo: 'bar'}) => { return foo + bar; });",
 150             errors
 151         },
 152         {
 153             code: "qux(function(baz, baz) { })",
 154             output: null, // Duplicate parameter names are a SyntaxError in arrow functions
 155             errors
 156         },
 157         {
 158             code: "qux(function( /* no params */ ) { })",
 159             output: "qux(( /* no params */ ) => { })",
 160             errors
 161         },
 162         {
 163             code: "qux(function( /* a */ foo /* b */ , /* c */ bar /* d */ , /* e */ baz /* f */ ) { return foo; })",
 164             output: "qux(( /* a */ foo /* b */ , /* c */ bar /* d */ , /* e */ baz /* f */ ) => { return foo; })",
 165             errors
 166         },
 167         {
 168             code: "qux(async function (foo = 1, bar = 2, baz = 3) { return baz; })",
 169             output: "qux(async (foo = 1, bar = 2, baz = 3) => { return baz; })",
 170             errors
 171         },
 172         {
 173             code: "qux(async function (foo = 1, bar = 2, baz = 3) { return this; }.bind(this))",
 174             output: "qux(async (foo = 1, bar = 2, baz = 3) => { return this; })",
 175             errors
 176         },
 177         {
 178             code: "foo((bar || function() {}).bind(this))",
 179             output: null,
 180             errors
 181         },
 182         {
 183             code: "foo(function() {}.bind(this).bind(obj))",
 184             output: "foo((() => {}).bind(obj))",
 185             errors
 186         },
 187
 188         // Optional chaining
 189         {
 190             code: "foo?.(function() {});",
 191             output: "foo?.(() => {});",
 192             errors
 193         },
 194         {
 195             code: "foo?.(function() { return this; }.bind(this));",
 196             output: "foo?.(() => { return this; });",
 197             errors
 198         },
 199         {
 200             code: "foo(function() { return this; }?.bind(this));",
 201             output: "foo(() => { return this; });",
 202             errors
 203         },
 204         {
 205             code: "foo((function() { return this; }?.bind)(this));",
 206             output: null,
 207             errors
 208         },
 209
 210         // https://github.com/eslint/eslint/issues/16718
 211         {
 212             code: `
 213             test(
 214                 function ()
 215                 { }
 216             );
 217             `,
 218             output: `
 219             test(
 220                 () =>
 221                 { }
 222             );
 223             `,
 224             errors
 225         },
 226         {
 227             code: `
 228             test(
 229                 function (
 230                     ...args
 231                 ) /* Lorem ipsum
 232                 dolor sit amet. */ {
 233                     return args;
 234                 }
 235             );
 236             `,
 237             output: `
 238             test(
 239                 (
 240                     ...args
 241                 ) => /* Lorem ipsum
 242                 dolor sit amet. */ {
 243                     return args;
 244                 }
 245             );
 246             `,
 247             errors
 248         }
 249     ]
 250 });