feat: add suggestions to use-isnan in binary expressions (#17996)

* feat: add suggestions to `use-isnan` in binary expressions * remove `>` `<` from fixes * move the array up * use Set * wip * small refactor * remove empty line * add multiple suggestions * change wording * suggest casting only in `==` and `!=`
eslint · Jan 29, 2024 · 2d11d46 · 2d11d46
1 parent c25b4af
commit 2d11d46
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diff --git a/lib/rules/use-isnan.js b/lib/rules/use-isnan.js
@@ -34,6 +34,7 @@ function isNaNIdentifier(node) {
 /** @type {import('../shared/types').Rule} */
 module.exports = {
     meta: {
+        hasSuggestions: true,
         type: "problem",
 
         docs: {
@@ -63,14 +64,45 @@ module.exports = {
             comparisonWithNaN: "Use the isNaN function to compare with NaN.",
             switchNaN: "'switch(NaN)' can never match a case clause. Use Number.isNaN instead of the switch.",
             caseNaN: "'case NaN' can never match. Use Number.isNaN before the switch.",
-            indexOfNaN: "Array prototype method '{{ methodName }}' cannot find NaN."
+            indexOfNaN: "Array prototype method '{{ methodName }}' cannot find NaN.",
+            replaceWithIsNaN: "Replace with Number.isNaN.",
+            replaceWithCastingAndIsNaN: "Replace with Number.isNaN cast to a Number."
         }
     },
 
     create(context) {
 
         const enforceForSwitchCase = !context.options[0] || context.options[0].enforceForSwitchCase;
         const enforceForIndexOf = context.options[0] && context.options[0].enforceForIndexOf;
+        const sourceCode = context.sourceCode;
+
+        const fixableOperators = new Set(["==", "===", "!=", "!=="]);
+        const castableOperators = new Set(["==", "!="]);
+
+        /**
+         * Get a fixer for a binary expression that compares to NaN.
+         * @param  {ASTNode} node The node to fix.
+         * @param {function(string): string} wrapValue A function that wraps the compared value with a fix.
+         * @returns {function(Fixer): Fix} The fixer function.
+         */
+        function getBinaryExpressionFixer(node, wrapValue) {
+            return fixer => {
+                const comparedValue = isNaNIdentifier(node.left) ? node.right : node.left;
+                const shouldWrap = comparedValue.type === "SequenceExpression";
+                const shouldNegate = node.operator[0] === "!";
+
+                const negation = shouldNegate ? "!" : "";
+                let comparedValueText = sourceCode.getText(comparedValue);
+
+                if (shouldWrap) {
+                    comparedValueText = `(${comparedValueText})`;
+                }
+
+                const fixedValue = wrapValue(comparedValueText);
+
+                return fixer.replaceText(node, `${negation}${fixedValue}`);
+            };
+        }
 
         /**
          * Checks the given `BinaryExpression` node for `foo === NaN` and other comparisons.
@@ -82,7 +114,29 @@ module.exports = {
                 /^(?:[<>]|[!=]=)=?$/u.test(node.operator) &&
                 (isNaNIdentifier(node.left) || isNaNIdentifier(node.right))
             ) {
-                context.report({ node, messageId: "comparisonWithNaN" });
+                const suggestedFixes = [];
+                const isFixable = fixableOperators.has(node.operator);
+                const isCastable = castableOperators.has(node.operator);
+
+                if (isFixable) {
+                    suggestedFixes.push({
+                        messageId: "replaceWithIsNaN",
+                        fix: getBinaryExpressionFixer(node, value => `Number.isNaN(${value})`)
+                    });
+                }
+
+                if (isCastable) {
+                    suggestedFixes.push({
+                        messageId: "replaceWithCastingAndIsNaN",
+                        fix: getBinaryExpressionFixer(node, value => `Number.isNaN(Number(${value}))`)
+                    });
+                }
+
+                context.report({
+                    node,
+                    messageId: "comparisonWithNaN",
+                    suggest: suggestedFixes
+                });
             }
         }