eslint/tests/lib/rules/no-var.js

   1 /**
   2  * @fileoverview Tests for no-var rule.
   3  * @author Jamund Ferguson
   4  */
   5
   6 "use strict";
   7
   8 //------------------------------------------------------------------------------
   9 // Requirements
  10 //------------------------------------------------------------------------------
  11
  12 const rule = require("../../../lib/rules/no-var"),
  13     { RuleTester } = require("../../../lib/rule-tester");
  14
  15 //------------------------------------------------------------------------------
  16 // Tests
  17 //------------------------------------------------------------------------------
  18
  19 const ruleTester = new RuleTester({ parserOptions: { ecmaVersion: 6 } });
  20
  21 ruleTester.run("no-var", rule, {
  22     valid: [
  23         "const JOE = 'schmoe';",
  24         "let moo = 'car';",
  25         {
  26             code: "const JOE = 'schmoe';",
  27             parserOptions: { ecmaFeatures: { globalReturn: true } }
  28         },
  29         {
  30             code: "let moo = 'car';",
  31             parserOptions: { ecmaFeatures: { globalReturn: true } }
  32         }
  33     ],
  34
  35     invalid: [
  36         {
  37             code: "var foo = bar;",
  38             output: "let foo = bar;",
  39             parserOptions: { ecmaFeatures: { globalReturn: true } },
  40             errors: [
  41                 {
  42                     messageId: "unexpectedVar",
  43                     type: "VariableDeclaration"
  44                 }
  45             ]
  46         },
  47         {
  48             code: "var foo = bar, toast = most;",
  49             output: "let foo = bar, toast = most;",
  50             parserOptions: { ecmaFeatures: { globalReturn: true } },
  51             errors: [
  52                 {
  53                     messageId: "unexpectedVar",
  54                     type: "VariableDeclaration"
  55                 }
  56             ]
  57         },
  58         {
  59             code: "var foo = bar; let toast = most;",
  60             output: "let foo = bar; let toast = most;",
  61             parserOptions: { ecmaFeatures: { globalReturn: true } },
  62             errors: [
  63                 {
  64                     messageId: "unexpectedVar",
  65                     type: "VariableDeclaration"
  66                 }
  67             ]
  68         },
  69         {
  70             code: "for (var a of b) { console.log(a); }",
  71             output: "for (let a of b) { console.log(a); }",
  72             parserOptions: { ecmaFeatures: { globalReturn: true } },
  73             errors: [
  74                 {
  75                     messageId: "unexpectedVar",
  76                     type: "VariableDeclaration"
  77                 }
  78             ]
  79         },
  80         {
  81             code: "for (var a in b) { console.log(a); }",
  82             output: "for (let a in b) { console.log(a); }",
  83             parserOptions: { ecmaFeatures: { globalReturn: true } },
  84             errors: [
  85                 {
  86                     messageId: "unexpectedVar",
  87                     type: "VariableDeclaration"
  88                 }
  89             ]
  90         },
  91         {
  92             code: "for (let a of b) { var c = 1; console.log(c); }",
  93             output: "for (let a of b) { let c = 1; console.log(c); }",
  94             parserOptions: { ecmaFeatures: { globalReturn: true } },
  95             errors: [
  96                 {
  97                     messageId: "unexpectedVar",
  98                     type: "VariableDeclaration"
  99                 }
 100             ]
 101         },
 102         {
 103             code: "for (var i = 0; i < list.length; ++i) { foo(i) }",
 104             output: "for (let i = 0; i < list.length; ++i) { foo(i) }",
 105             parserOptions: { ecmaFeatures: { globalReturn: true } },
 106             errors: [
 107                 { messageId: "unexpectedVar", type: "VariableDeclaration" }
 108             ]
 109         },
 110         {
 111             code: "for (var i = 0, i = 0; false;);",
 112             output: null,
 113             parserOptions: { ecmaFeatures: { globalReturn: true } },
 114             errors: [
 115                 { messageId: "unexpectedVar", type: "VariableDeclaration" }
 116             ]
 117         },
 118         {
 119             code: "var i = 0; for (var i = 1; false;); console.log(i);",
 120             output: null,
 121             parserOptions: { ecmaFeatures: { globalReturn: true } },
 122             errors: [
 123                 { messageId: "unexpectedVar", type: "VariableDeclaration" },
 124                 { messageId: "unexpectedVar", type: "VariableDeclaration" }
 125             ]
 126         },
 127
 128         // Not fix if it's redeclared or it's used from outside of the scope or it's declared on a case chunk.
 129         {
 130             code: "var a, b, c; var a;",
 131             output: null,
 132             parserOptions: { ecmaFeatures: { globalReturn: true } },
 133             errors: [
 134                 { messageId: "unexpectedVar" },
 135                 { messageId: "unexpectedVar" }
 136             ]
 137         },
 138         {
 139             code: "var a; if (b) { var a; }",
 140             output: null,
 141             parserOptions: { ecmaFeatures: { globalReturn: true } },
 142             errors: [
 143                 { messageId: "unexpectedVar" },
 144                 { messageId: "unexpectedVar" }
 145             ]
 146         },
 147         {
 148             code: "if (foo) { var a, b, c; } a;",
 149             output: null,
 150             parserOptions: { ecmaFeatures: { globalReturn: true } },
 151             errors: [
 152                 { messageId: "unexpectedVar" }
 153             ]
 154         },
 155         {
 156             code: "for (var i = 0; i < 10; ++i) {} i;",
 157             output: null,
 158             parserOptions: { ecmaFeatures: { globalReturn: true } },
 159             errors: [
 160                 { messageId: "unexpectedVar" }
 161             ]
 162         },
 163         {
 164             code: "for (var a in obj) {} a;",
 165             output: null,
 166             parserOptions: { ecmaFeatures: { globalReturn: true } },
 167             errors: [
 168                 { messageId: "unexpectedVar" }
 169             ]
 170         },
 171         {
 172             code: "for (var a of list) {} a;",
 173             output: null,
 174             parserOptions: { ecmaFeatures: { globalReturn: true } },
 175             errors: [
 176                 { messageId: "unexpectedVar" }
 177             ]
 178         },
 179         {
 180             code: "switch (a) { case 0: var b = 1 }",
 181             output: null,
 182             parserOptions: { ecmaFeatures: { globalReturn: true } },
 183             errors: [
 184                 { messageId: "unexpectedVar" }
 185             ]
 186         },
 187
 188         // Don't fix if the variable is in a loop and the behavior might change.
 189         {
 190             code: "for (var a of b) { arr.push(() => a); }",
 191             output: null,
 192             parserOptions: { ecmaFeatures: { globalReturn: true } },
 193             errors: [
 194                 { messageId: "unexpectedVar" }
 195             ]
 196         },
 197         {
 198             code: "for (let a of b) { var c; console.log(c); c = 'hello'; }",
 199             output: null,
 200             parserOptions: { ecmaFeatures: { globalReturn: true } },
 201             errors: [
 202                 { messageId: "unexpectedVar" }
 203             ]
 204         },
 205
 206         // https://github.com/eslint/eslint/issues/7950
 207         {
 208             code: "var a = a",
 209             output: null,
 210             parserOptions: { ecmaFeatures: { globalReturn: true } },
 211             errors: [
 212                 { messageId: "unexpectedVar" }
 213             ]
 214         },
 215         {
 216             code: "var {a = a} = {}",
 217             output: null,
 218             parserOptions: { ecmaVersion: 2015, ecmaFeatures: { globalReturn: true } },
 219             errors: [
 220                 { messageId: "unexpectedVar" }
 221             ]
 222         },
 223         {
 224             code: "var {a = b, b} = {}",
 225             output: null,
 226             parserOptions: { ecmaVersion: 2015, ecmaFeatures: { globalReturn: true } },
 227             errors: [
 228                 { messageId: "unexpectedVar" }
 229             ]
 230         },
 231         {
 232             code: "var {a, b = a} = {}",
 233             output: "let {a, b = a} = {}",
 234             parserOptions: { ecmaVersion: 2015, ecmaFeatures: { globalReturn: true } },
 235             errors: [
 236                 { messageId: "unexpectedVar" }
 237             ]
 238         },
 239         {
 240             code: "var a = b, b = 1",
 241             output: null,
 242             parserOptions: { ecmaVersion: 2015, ecmaFeatures: { globalReturn: true } },
 243             errors: [
 244                 { messageId: "unexpectedVar" }
 245             ]
 246         },
 247         {
 248             code: "var a = b; var b = 1",
 249             output: "let a = b; var b = 1",
 250             parserOptions: { ecmaVersion: 2015, ecmaFeatures: { globalReturn: true } },
 251             errors: [
 252                 { messageId: "unexpectedVar" },
 253                 { messageId: "unexpectedVar" }
 254             ]
 255         },
 256
 257         /*
 258          * This case is not in TDZ, but it's very hard to distinguish the reference is in TDZ or not.
 259          * So this rule does not fix it for safe.
 260          */
 261         {
 262             code: "function foo() { a } var a = 1; foo()",
 263             output: null,
 264             parserOptions: { ecmaVersion: 2015, ecmaFeatures: { globalReturn: true } },
 265             errors: [
 266                 { messageId: "unexpectedVar" }
 267             ]
 268         },
 269
 270         // https://github.com/eslint/eslint/issues/7961
 271         {
 272             code: "if (foo) var bar = 1;",
 273             output: null,
 274             parserOptions: { ecmaFeatures: { globalReturn: true } },
 275             errors: [
 276                 { messageId: "unexpectedVar", type: "VariableDeclaration" }
 277             ]
 278         },
 279
 280         // https://github.com/eslint/eslint/issues/9520
 281         {
 282             code: "var foo = 1",
 283             output: null,
 284             errors: [{ messageId: "unexpectedVar" }]
 285         },
 286         {
 287             code: "{ var foo = 1 }",
 288             output: null,
 289             errors: [{ messageId: "unexpectedVar" }]
 290         },
 291         {
 292             code: "if (true) { var foo = 1 }",
 293             output: null,
 294             errors: [{ messageId: "unexpectedVar" }]
 295         },
 296         {
 297             code: "var foo = 1",
 298             output: "let foo = 1",
 299             parserOptions: { ecmaVersion: 6, sourceType: "module" },
 300             errors: [{ messageId: "unexpectedVar" }]
 301         },
 302
 303         // https://github.com/eslint/eslint/issues/11594
 304         {
 305             code: "declare var foo = 2;",
 306             output: "declare let foo = 2;",
 307             parser: require.resolve("../../fixtures/parsers/typescript-parsers/declare-var"),
 308             parserOptions: { ecmaVersion: 6, sourceType: "module" },
 309             errors: [{ messageId: "unexpectedVar" }]
 310         },
 311
 312         // https://github.com/eslint/eslint/issues/11830
 313         {
 314             code: "function foo() { var let; }",
 315             output: null,
 316             errors: [{ messageId: "unexpectedVar" }]
 317         },
 318         {
 319             code: "function foo() { var { let } = {}; }",
 320             output: null,
 321             errors: [{ messageId: "unexpectedVar" }]
 322         }
 323     ]
 324 });