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Update: Add enforceForSwitchCase option to use-isnan #12106

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merged 2 commits into from Sep 29, 2019
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Update: Add enforceForSwitchCase option to use-isnan #12106

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23ce506
Update: Add enforceForSwitchCase option to use-isnan
mdjermanovic Aug 17, 2019
5c9a098
Check switch(NaN)
mdjermanovic Sep 17, 2019
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47 changes: 47 additions & 0 deletions docs/rules/use-isnan.md
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Expand Up @@ -40,3 +40,50 @@ if (!isNaN(foo)) {
// ...
}
```

## Options

This rule has an object option, with one option:

* `"enforceForSwitchCase"` when set to `true` disallows `case NaN` in `switch` statements. Default is `false`, meaning
that this rule by default does not warn about `case NaN`.

### enforceForSwitchCase

The `switch` statement internally uses the `===` operator to match the expression's value to a case clause.
Therefore, it can never match `case NaN`.

Set `"enforceForSwitchCase"` to `true` if you want this rule to report `case NaN` in `switch` statements.

Examples of **incorrect** code for this rule with `"enforceForSwitchCase"` option set to `true`:

```js
/*eslint use-isnan: ["error", {"enforceForSwitchCase": true}]*/

switch (foo) {
case NaN:
bar();
break;
case 1:
baz();
break;
// ...
}
```

Examples of **correct** code for this rule with `"enforceForSwitchCase"` option set to `true`:

```js
/*eslint use-isnan: ["error", {"enforceForSwitchCase": true}]*/

if (Number.isNaN(foo)) {
bar();
} else {
switch (foo) {
case 1:
baz();
break;
// ...
}
}
```
30 changes: 27 additions & 3 deletions lib/rules/use-isnan.js
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Expand Up @@ -20,18 +20,42 @@ module.exports = {
url: "https://eslint.org/docs/rules/use-isnan"
},

schema: [],
schema: [
{
type: "object",
properties: {
enforceForSwitchCase: {
type: "boolean",
default: false
}
},
additionalProperties: false
}
],

messages: {
useIsNaN: "Use the isNaN function to compare with NaN."
comparisonWithNaN: "Use the isNaN function to compare with NaN.",
caseNaN: "'case NaN' can never match. Use Number.isNaN before the switch."
}
},

create(context) {

const enforceForSwitchCase = context.options[0] && context.options[0].enforceForSwitchCase;

return {
BinaryExpression(node) {
if (/^(?:[<>]|[!=]=)=?$/u.test(node.operator) && (node.left.name === "NaN" || node.right.name === "NaN")) {
context.report({ node, messageId: "useIsNaN" });
context.report({ node, messageId: "comparisonWithNaN" });
}
},
SwitchCase(node) {
if (enforceForSwitchCase) {
const test = node.test;

if (test && test.type === "Identifier" && test.name === "NaN") {
context.report({ node, messageId: "caseNaN" });
}
}
}
};
Expand Down
116 changes: 98 additions & 18 deletions tests/lib/rules/use-isnan.js
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Expand Up @@ -18,7 +18,7 @@ const rule = require("../../../lib/rules/use-isnan"),

const ruleTester = new RuleTester();

const error = { messageId: "useIsNaN", type: "BinaryExpression" };
const comparisonError = { messageId: "comparisonWithNaN", type: "BinaryExpression" };

ruleTester.run("use-isnan", rule, {
valid: [
Expand All @@ -35,72 +35,152 @@ ruleTester.run("use-isnan", rule, {
"foo(2 * NaN)",
"foo(NaN / 2)",
"foo(2 / NaN)",
"var x; if (x = NaN) { }"
"var x; if (x = NaN) { }",

//------------------------------------------------------------------------------
// enforceForSwitchCase
//------------------------------------------------------------------------------

"switch(foo) { case NaN: break; }",
{
code: "switch(foo) { case NaN: break; }",
options: [{}]
},
{
code: "switch(foo) { case NaN: break; }",
options: [{ enforceForSwitchCase: false }]
},
{
code: "switch(foo) { case bar: break; case NaN: break; default: break; }",
options: [{ enforceForSwitchCase: false }]
},
{
code: "switch(foo) {}",
options: [{ enforceForSwitchCase: true }]
},
{
code: "switch(NaN) {}",
options: [{ enforceForSwitchCase: true }]
},
{
code: "switch(foo) { case Nan: break }",
options: [{ enforceForSwitchCase: true }]
},
{
code: "switch(foo) { case 'NaN': break }",
options: [{ enforceForSwitchCase: true }]
},
{
code: "switch(foo) { case foo(NaN): break }",
options: [{ enforceForSwitchCase: true }]
},
{
code: "switch(foo) { case bar: break; case 1: break; default: break; }",
options: [{ enforceForSwitchCase: true }]
}
],
invalid: [
{
code: "123 == NaN;",
errors: [error]
errors: [comparisonError]
},
{
code: "123 === NaN;",
errors: [error]
errors: [comparisonError]
},
{
code: "NaN === \"abc\";",
errors: [error]
errors: [comparisonError]
},
{
code: "NaN == \"abc\";",
errors: [error]
errors: [comparisonError]
},
{
code: "123 != NaN;",
errors: [error]
errors: [comparisonError]
},
{
code: "123 !== NaN;",
errors: [error]
errors: [comparisonError]
},
{
code: "NaN !== \"abc\";",
errors: [error]
errors: [comparisonError]
},
{
code: "NaN != \"abc\";",
errors: [error]
errors: [comparisonError]
},
{
code: "NaN < \"abc\";",
errors: [error]
errors: [comparisonError]
},
{
code: "\"abc\" < NaN;",
errors: [error]
errors: [comparisonError]
},
{
code: "NaN > \"abc\";",
errors: [error]
errors: [comparisonError]
},
{
code: "\"abc\" > NaN;",
errors: [error]
errors: [comparisonError]
},
{
code: "NaN <= \"abc\";",
errors: [error]
errors: [comparisonError]
},
{
code: "\"abc\" <= NaN;",
errors: [error]
errors: [comparisonError]
},
{
code: "NaN >= \"abc\";",
errors: [error]
errors: [comparisonError]
},
{
code: "\"abc\" >= NaN;",
errors: [error]
errors: [comparisonError]
},

//------------------------------------------------------------------------------
// enforceForSwitchCase
//------------------------------------------------------------------------------

{
code: "switch(foo) { case NaN: }",
options: [{ enforceForSwitchCase: true }],
errors: [{ messageId: "caseNaN", type: "SwitchCase", column: 15 }]
},
{
code: "switch(foo) { case NaN: break; }",
options: [{ enforceForSwitchCase: true }],
errors: [{ messageId: "caseNaN", type: "SwitchCase", column: 15 }]
},
{
code: "switch(foo) { case (NaN): break; }",
options: [{ enforceForSwitchCase: true }],
errors: [{ messageId: "caseNaN", type: "SwitchCase", column: 15 }]
},
{
code: "switch(foo) { case bar: break; case NaN: break; default: break; }",
options: [{ enforceForSwitchCase: true }],
errors: [{ messageId: "caseNaN", type: "SwitchCase", column: 32 }]
},
{
code: "switch(foo) { case bar: case NaN: default: break; }",
options: [{ enforceForSwitchCase: true }],
errors: [{ messageId: "caseNaN", type: "SwitchCase", column: 25 }]
},
{
code: "switch(foo) { case bar: break; case NaN: break; case baz: break; case NaN: break;}",
options: [{ enforceForSwitchCase: true }],
errors: [
{ messageId: "caseNaN", type: "SwitchCase", column: 32 },
{ messageId: "caseNaN", type: "SwitchCase", column: 66 }
]
}
]
});