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Commit73596cb

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mdjermanovicmysticatea
authored andcommitted
Update: Add enforceForSwitchCase option to use-isnan (#12106)
1 parentd592a24 commit73596cb

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3 files changed

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‎docs/rules/use-isnan.md‎

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@@ -40,3 +40,66 @@ if (!isNaN(foo)) {
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// ...
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}
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```
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##Options
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This rule has an object option, with one option:
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*`"enforceForSwitchCase"` when set to`true` disallows`case NaN` and`switch(NaN)` in`switch` statements. Default is`false`, meaning
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that this rule by default does not warn about`case NaN` or`switch(NaN)`.
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###enforceForSwitchCase
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The`switch` statement internally uses the`===` comparison to match the expression's value to a case clause.
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Therefore, it can never match`case NaN`. Also,`switch(NaN)` can never match a case clause.
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Set`"enforceForSwitchCase"` to`true` if you want this rule to report`case NaN` and`switch(NaN)` in`switch` statements.
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Examples of**incorrect** code for this rule with`"enforceForSwitchCase"` option set to`true`:
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```js
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/*eslint use-isnan: ["error", {"enforceForSwitchCase": true}]*/
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switch (foo) {
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caseNaN:
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bar();
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break;
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case1:
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baz();
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break;
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// ...
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}
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switch (NaN) {
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case a:
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bar();
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break;
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case b:
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baz();
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break;
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// ...
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}
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```
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Examples of**correct** code for this rule with`"enforceForSwitchCase"` option set to`true`:
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```js
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/*eslint use-isnan: ["error", {"enforceForSwitchCase": true}]*/
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if (Number.isNaN(foo)) {
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bar();
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}else {
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switch (foo) {
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case1:
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baz();
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break;
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// ...
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}
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}
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if (Number.isNaN(a)) {
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bar();
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}elseif (Number.isNaN(b)) {
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baz();
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}// ...
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```

‎lib/rules/use-isnan.js‎

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"use strict";
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//------------------------------------------------------------------------------
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// Helpers
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//------------------------------------------------------------------------------
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/**
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* Determines if the given node is a NaN `Identifier` node.
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*@param {ASTNode|null} node The node to check.
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*@returns {boolean} `true` if the node is 'NaN' identifier.
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*/
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functionisNaNIdentifier(node){
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returnBoolean(node)&&node.type==="Identifier"&&node.name==="NaN";
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}
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//------------------------------------------------------------------------------
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// Rule Definition
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//------------------------------------------------------------------------------
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url:"https://eslint.org/docs/rules/use-isnan"
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},
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schema:[],
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schema:[
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{
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type:"object",
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properties:{
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enforceForSwitchCase:{
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type:"boolean",
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default:false
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}
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},
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additionalProperties:false
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}
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],
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messages:{
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useIsNaN:"Use the isNaN function to compare with NaN."
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comparisonWithNaN:"Use the isNaN function to compare with NaN.",
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switchNaN:"'switch(NaN)' can never match a case clause. Use Number.isNaN instead of the switch.",
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caseNaN:"'case NaN' can never match. Use Number.isNaN before the switch."
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}
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},
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create(context){
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return{
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BinaryExpression(node){
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if(/^(?:[<>]|[!=]=)=?$/u.test(node.operator)&&(node.left.name==="NaN"||node.right.name==="NaN")){
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context.report({ node,messageId:"useIsNaN"});
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constenforceForSwitchCase=context.options[0]&&context.options[0].enforceForSwitchCase;
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/**
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* Checks the given `BinaryExpression` node.
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*@param {ASTNode} node The node to check.
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*@returns {void}
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*/
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functioncheckBinaryExpression(node){
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if(
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/^(?:[<>]|[!=]=)=?$/u.test(node.operator)&&
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(isNaNIdentifier(node.left)||isNaNIdentifier(node.right))
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){
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context.report({ node,messageId:"comparisonWithNaN"});
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}
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}
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/**
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* Checks the discriminant and all case clauses of the given `SwitchStatement` node.
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*@param {ASTNode} node The node to check.
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*@returns {void}
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*/
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functioncheckSwitchStatement(node){
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if(isNaNIdentifier(node.discriminant)){
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context.report({ node,messageId:"switchNaN"});
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}
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for(constswitchCaseofnode.cases){
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if(isNaNIdentifier(switchCase.test)){
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context.report({node:switchCase,messageId:"caseNaN"});
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}
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}
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}
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constlisteners={
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BinaryExpression:checkBinaryExpression
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};
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if(enforceForSwitchCase){
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listeners.SwitchStatement=checkSwitchStatement;
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}
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returnlisteners;
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}
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};

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