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feat: valid-typeof: always ban undefined #15635

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merged 6 commits into from Mar 5, 2022
Merged

feat: valid-typeof: always ban undefined #15635

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7dda297
feat: `valid-typeof`: always ban `undefined`
Zzzen Feb 24, 2022
51073f5
change error message and check definition of `undefined`
Zzzen Feb 24, 2022
f4a96de
check string literal first
Zzzen Feb 26, 2022
f288a78
add suggestions
Zzzen Feb 27, 2022
bf98c4d
Apply suggestions from code review
Zzzen Mar 4, 2022
f79dcde
suggest string when `requireStringLiterals` is on
Zzzen Mar 4, 2022
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21 changes: 21 additions & 0 deletions lib/rules/valid-typeof.js
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Expand Up @@ -44,6 +44,21 @@ 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
Expand All @@ -59,6 +74,10 @@ module.exports = {

return {

Program() {
globalScope = context.getScope();
},

UnaryExpression(node) {
if (isTypeofExpression(node)) {
const parent = context.getAncestors().pop();
Expand All @@ -74,6 +93,8 @@ module.exports = {
}
} else if (requireStringLiterals && !isTypeofExpression(sibling)) {
context.report({ node: sibling, messageId: "notString" });
} else if (sibling.type === "Identifier" && sibling.name === "undefined" && isReferenceToGlobalVariable(sibling)) {
context.report({ node: sibling, messageId: "invalidValue" });
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}
}
}
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5 changes: 5 additions & 0 deletions tests/lib/rules/valid-typeof.js
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Expand Up @@ -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 }]
Expand Down Expand Up @@ -136,6 +137,10 @@ ruleTester.run("valid-typeof", rule, {
options: [{ requireStringLiterals: true }],
errors: [{ messageId: "invalidValue", type: "Literal" }]
},
{
code: "if (typeof bar !== undefined) {}",
errors: [{ messageId: "invalidValue", type: "Identifier" }]
},
{
code: "typeof foo == Object",
options: [{ requireStringLiterals: true }],
Expand Down