feat: valid-typeof always ban undefined (#15635)

* feat: `valid-typeof`: always ban `undefined` * change error message and check definition of `undefined` * check string literal first * add suggestions * Apply suggestions from code review Co-authored-by: Milos Djermanovic <milos.djermanovic@gmail.com> * suggest string when `requireStringLiterals` is on Co-authored-by: Milos Djermanovic <milos.djermanovic@gmail.com>
eslint · Mar 5, 2022 · 57b8a57 · 57b8a57
1 parent 8f675b1
commit 57b8a57
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Showing 2 changed files with 89 additions and 4 deletions.
diff --git a/lib/rules/valid-typeof.js b/lib/rules/valid-typeof.js
@@ -19,6 +19,8 @@ module.exports = {
             url: "https://eslint.org/docs/rules/valid-typeof"
         },
 
+        hasSuggestions: true,
+
         schema: [
             {
                 type: "object",
@@ -33,7 +35,8 @@ module.exports = {
         ],
         messages: {
             invalidValue: "Invalid typeof comparison value.",
-            notString: "Typeof comparisons should be to string literals."
+            notString: "Typeof comparisons should be to string literals.",
+            suggestString: 'Use `"{{type}}"` instead of `{{type}}`.'
         }
     },
 
@@ -44,6 +47,21 @@ module.exports = {
 
         const requireStringLiterals = context.options[0] && context.options[0].requireStringLiterals;
 
+        let globalScope;
+
+        /**
+         * Checks whether the given node represents a reference to a global variable that is not declared in the source code.
+         * These identifiers will be allowed, as it is assumed that user has no control over the names of external global variables.
+         * @param {ASTNode} node `Identifier` node to check.
+         * @returns {boolean} `true` if the node is a reference to a global variable.
+         */
+        function isReferenceToGlobalVariable(node) {
+            const variable = globalScope.set.get(node.name);
+
+            return variable && variable.defs.length === 0 &&
+                variable.references.some(ref => ref.identifier === node);
+        }
+
         /**
          * Determines whether a node is a typeof expression.
          * @param {ASTNode} node The node
@@ -59,6 +77,10 @@ module.exports = {
 
         return {
 
+            Program() {
+                globalScope = context.getScope();
+            },
+
             UnaryExpression(node) {
                 if (isTypeofExpression(node)) {
                     const parent = context.getAncestors().pop();
@@ -72,6 +94,20 @@ module.exports = {
                             if (VALID_TYPES.indexOf(value) === -1) {
                                 context.report({ node: sibling, messageId: "invalidValue" });
                             }
+                        } else if (sibling.type === "Identifier" && sibling.name === "undefined" && isReferenceToGlobalVariable(sibling)) {
+                            context.report({
+                                node: sibling,
+                                messageId: requireStringLiterals ? "notString" : "invalidValue",
+                                suggest: [
+                                    {
+                                        messageId: "suggestString",
+                                        data: { type: "undefined" },
+                                        fix(fixer) {
+                                            return fixer.replaceText(sibling, '"undefined"');
+                                        }
+                                    }
+                                ]
+                            });
                         } else if (requireStringLiterals && !isTypeofExpression(sibling)) {
                             context.report({ node: sibling, messageId: "notString" });
                         }

diff --git a/tests/lib/rules/valid-typeof.js b/tests/lib/rules/valid-typeof.js
@@ -45,6 +45,7 @@ ruleTester.run("valid-typeof", rule, {
         "typeof(foo) == 'string'",
         "typeof(foo) != 'string'",
         "var oddUse = typeof foo + 'thing'",
+        "function f(undefined) { typeof x === undefined }",
         {
             code: "typeof foo === 'number'",
             options: [{ requireStringLiterals: true }]
@@ -136,6 +137,21 @@ ruleTester.run("valid-typeof", rule, {
             options: [{ requireStringLiterals: true }],
             errors: [{ messageId: "invalidValue", type: "Literal" }]
         },
+        {
+            code: "if (typeof bar !== undefined) {}",
+            errors: [
+                {
+                    messageId: "invalidValue",
+                    type: "Identifier",
+                    suggestions: [
+                        {
+                            messageId: "suggestString",
+                            data: { type: "undefined" },
+                            output: 'if (typeof bar !== "undefined") {}'
+                        }
+                    ]
+                }]
+        },
         {
             code: "typeof foo == Object",
             options: [{ requireStringLiterals: true }],
@@ -144,17 +160,50 @@ ruleTester.run("valid-typeof", rule, {
         {
             code: "typeof foo === undefined",
             options: [{ requireStringLiterals: true }],
-            errors: [{ messageId: "notString", type: "Identifier" }]
+            errors: [
+                {
+                    messageId: "notString",
+                    type: "Identifier",
+                    suggestions: [
+                        {
+                            messageId: "suggestString",
+                            data: { type: "undefined" },
+                            output: 'typeof foo === "undefined"'
+                        }
+                    ]
+                }]
         },
         {
             code: "undefined === typeof foo",
             options: [{ requireStringLiterals: true }],
-            errors: [{ messageId: "notString", type: "Identifier" }]
+            errors: [
+                {
+                    messageId: "notString",
+                    type: "Identifier",
+                    suggestions: [
+                        {
+                            messageId: "suggestString",
+                            data: { type: "undefined" },
+                            output: '"undefined" === typeof foo'
+                        }
+                    ]
+                }]
         },
         {
             code: "undefined == typeof foo",
             options: [{ requireStringLiterals: true }],
-            errors: [{ messageId: "notString", type: "Identifier" }]
+            errors: [
+                {
+                    messageId: "notString",
+                    type: "Identifier",
+                    suggestions: [
+                        {
+                            messageId: "suggestString",
+                            data: { type: "undefined" },
+                            output: '"undefined" == typeof foo'
+                        }
+                    ]
+                }]
         },
         {
             code: "typeof foo === `undefined${foo}`",