eslint/tests/lib/rules/no-unused-expressions.js

   1 /**
   2  * @fileoverview Tests for no-unused-expressions rule.
   3  * @author Michael Ficarra
   4  */
   5
   6 "use strict";
   7
   8 //------------------------------------------------------------------------------
   9 // Requirements
  10 //------------------------------------------------------------------------------
  11
  12 const rule = require("../../../lib/rules/no-unused-expressions"),
  13     { RuleTester } = require("../../../lib/rule-tester");
  14
  15 //------------------------------------------------------------------------------
  16 // Tests
  17 //------------------------------------------------------------------------------
  18
  19 const ruleTester = new RuleTester();
  20
  21 ruleTester.run("no-unused-expressions", rule, {
  22     valid: [
  23         "function f(){}",
  24         "a = b",
  25         "new a",
  26         "{}",
  27         "f(); g()",
  28         "i++",
  29         "a()",
  30         { code: "a && a()", options: [{ allowShortCircuit: true }] },
  31         { code: "a() || (b = c)", options: [{ allowShortCircuit: true }] },
  32         { code: "a ? b() : c()", options: [{ allowTernary: true }] },
  33         { code: "a ? b() || (c = d) : e()", options: [{ allowShortCircuit: true, allowTernary: true }] },
  34         "delete foo.bar",
  35         "void new C",
  36         "\"use strict\";",
  37         "\"directive one\"; \"directive two\"; f();",
  38         "function foo() {\"use strict\"; return true; }",
  39         { code: "var foo = () => {\"use strict\"; return true; }", parserOptions: { ecmaVersion: 6 } },
  40         "function foo() {\"directive one\"; \"directive two\"; f(); }",
  41         "function foo() { var foo = \"use strict\"; return true; }",
  42         {
  43             code: "function* foo(){ yield 0; }",
  44             parserOptions: { ecmaVersion: 6 }
  45         },
  46         {
  47             code: "async function foo() { await 5; }",
  48             parserOptions: { ecmaVersion: 8 }
  49         },
  50         {
  51             code: "async function foo() { await foo.bar; }",
  52             parserOptions: { ecmaVersion: 8 }
  53         },
  54         {
  55             code: "async function foo() { bar && await baz; }",
  56             options: [{ allowShortCircuit: true }],
  57             parserOptions: { ecmaVersion: 8 }
  58         },
  59         {
  60             code: "async function foo() { foo ? await bar : await baz; }",
  61             options: [{ allowTernary: true }],
  62             parserOptions: { ecmaVersion: 8 }
  63         },
  64         {
  65             code: "tag`tagged template literal`",
  66             options: [{ allowTaggedTemplates: true }],
  67             parserOptions: { ecmaVersion: 6 }
  68         },
  69         {
  70             code: "shouldNotBeAffectedByAllowTemplateTagsOption()",
  71             options: [{ allowTaggedTemplates: true }],
  72             parserOptions: { ecmaVersion: 6 }
  73         },
  74         {
  75             code: "import(\"foo\")",
  76             parserOptions: { ecmaVersion: 11 }
  77         },
  78         {
  79             code: "func?.(\"foo\")",
  80             parserOptions: { ecmaVersion: 11 }
  81         },
  82         {
  83             code: "obj?.foo(\"bar\")",
  84             parserOptions: { ecmaVersion: 11 }
  85         },
  86
  87         // JSX
  88         {
  89             code: "<div />",
  90             parserOptions: { ecmaFeatures: { jsx: true } }
  91         },
  92         {
  93             code: "<></>",
  94             parserOptions: { ecmaFeatures: { jsx: true } }
  95         },
  96         {
  97             code: "var partial = <div />",
  98             parserOptions: { ecmaFeatures: { jsx: true } }
  99         },
 100         {
 101             code: "var partial = <div />",
 102             options: [{ enforceForJSX: true }],
 103             parserOptions: { ecmaFeatures: { jsx: true } }
 104         },
 105         {
 106             code: "var partial = <></>",
 107             options: [{ enforceForJSX: true }],
 108             parserOptions: { ecmaFeatures: { jsx: true } }
 109         }
 110     ],
 111     invalid: [
 112         { code: "0", errors: [{ messageId: "unusedExpression", type: "ExpressionStatement" }] },
 113         { code: "a", errors: [{ messageId: "unusedExpression", type: "ExpressionStatement" }] },
 114         { code: "f(), 0", errors: [{ messageId: "unusedExpression", type: "ExpressionStatement" }] },
 115         { code: "{0}", errors: [{ messageId: "unusedExpression", type: "ExpressionStatement" }] },
 116         { code: "[]", errors: [{ messageId: "unusedExpression", type: "ExpressionStatement" }] },
 117         { code: "a && b();", errors: [{ messageId: "unusedExpression", type: "ExpressionStatement" }] },
 118         { code: "a() || false", errors: [{ messageId: "unusedExpression", type: "ExpressionStatement" }] },
 119         { code: "a || (b = c)", errors: [{ messageId: "unusedExpression", type: "ExpressionStatement" }] },
 120         { code: "a ? b() || (c = d) : e", errors: [{ messageId: "unusedExpression", type: "ExpressionStatement" }] },
 121         {
 122             code: "`untagged template literal`",
 123             parserOptions: { ecmaVersion: 6 },
 124             errors: [{ messageId: "unusedExpression" }]
 125         },
 126         {
 127             code: "tag`tagged template literal`",
 128             parserOptions: { ecmaVersion: 6 },
 129             errors: [{ messageId: "unusedExpression" }]
 130         },
 131         { code: "a && b()", options: [{ allowTernary: true }], errors: [{ messageId: "unusedExpression", type: "ExpressionStatement" }] },
 132         { code: "a ? b() : c()", options: [{ allowShortCircuit: true }], errors: [{ messageId: "unusedExpression", type: "ExpressionStatement" }] },
 133         { code: "a || b", options: [{ allowShortCircuit: true }], errors: [{ messageId: "unusedExpression", type: "ExpressionStatement" }] },
 134         { code: "a() && b", options: [{ allowShortCircuit: true }], errors: [{ messageId: "unusedExpression", type: "ExpressionStatement" }] },
 135         { code: "a ? b : 0", options: [{ allowTernary: true }], errors: [{ messageId: "unusedExpression", type: "ExpressionStatement" }] },
 136         { code: "a ? b : c()", options: [{ allowTernary: true }], errors: [{ messageId: "unusedExpression", type: "ExpressionStatement" }] },
 137         { code: "foo.bar;", errors: [{ messageId: "unusedExpression", type: "ExpressionStatement" }] },
 138         { code: "!a", errors: [{ messageId: "unusedExpression", type: "ExpressionStatement" }] },
 139         { code: "+a", errors: [{ messageId: "unusedExpression", type: "ExpressionStatement" }] },
 140         { code: "\"directive one\"; f(); \"directive two\";", errors: [{ messageId: "unusedExpression", type: "ExpressionStatement" }] },
 141         { code: "function foo() {\"directive one\"; f(); \"directive two\"; }", errors: [{ messageId: "unusedExpression", type: "ExpressionStatement" }] },
 142         { code: "if (0) { \"not a directive\"; f(); }", errors: [{ messageId: "unusedExpression", type: "ExpressionStatement" }] },
 143         { code: "function foo() { var foo = true; \"use strict\"; }", errors: [{ messageId: "unusedExpression", type: "ExpressionStatement" }] },
 144         { code: "var foo = () => { var foo = true; \"use strict\"; }", parserOptions: { ecmaVersion: 6 }, errors: [{ messageId: "unusedExpression", type: "ExpressionStatement" }] },
 145         {
 146             code: "`untagged template literal`",
 147             options: [{ allowTaggedTemplates: true }],
 148             parserOptions: { ecmaVersion: 6 },
 149             errors: [{ messageId: "unusedExpression" }]
 150         },
 151         {
 152             code: "`untagged template literal`",
 153             options: [{ allowTaggedTemplates: false }],
 154             parserOptions: { ecmaVersion: 6 },
 155             errors: [{ messageId: "unusedExpression" }]
 156         },
 157         {
 158             code: "tag`tagged template literal`",
 159             options: [{ allowTaggedTemplates: false }],
 160             parserOptions: { ecmaVersion: 6 },
 161             errors: [{ messageId: "unusedExpression" }]
 162         },
 163
 164         // Optional chaining
 165         {
 166             code: "obj?.foo",
 167             parserOptions: { ecmaVersion: 2020 },
 168             errors: [{ messageId: "unusedExpression", type: "ExpressionStatement" }]
 169         },
 170         {
 171             code: "obj?.foo.bar",
 172             parserOptions: { ecmaVersion: 2020 },
 173             errors: [{ messageId: "unusedExpression", type: "ExpressionStatement" }]
 174         },
 175         {
 176             code: "obj?.foo().bar",
 177             parserOptions: { ecmaVersion: 2020 },
 178             errors: [{ messageId: "unusedExpression", type: "ExpressionStatement" }]
 179         },
 180
 181         // JSX
 182         {
 183             code: "<div />",
 184             options: [{ enforceForJSX: true }],
 185             parserOptions: { ecmaFeatures: { jsx: true } },
 186             errors: [{ messageId: "unusedExpression", type: "ExpressionStatement" }]
 187         },
 188         {
 189             code: "<></>",
 190             options: [{ enforceForJSX: true }],
 191             parserOptions: { ecmaFeatures: { jsx: true } },
 192             errors: [{ messageId: "unusedExpression", type: "ExpressionStatement" }]
 193         }
 194     ]
 195 });