/**
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* @fileoverview Rule to flag references to the undefined variable.
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* @author Michael Ficarra
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*/
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"use strict";
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//------------------------------------------------------------------------------
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// Rule Definition
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//------------------------------------------------------------------------------
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module.exports = {
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meta: {
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type: "suggestion",
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docs: {
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description: "disallow the use of `undefined` as an identifier",
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category: "Variables",
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recommended: false,
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url: "https://eslint.org/docs/rules/no-undefined"
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},
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schema: [],
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messages: {
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unexpectedUndefined: "Unexpected use of undefined."
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}
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},
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create(context) {
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/**
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* Report an invalid "undefined" identifier node.
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* @param {ASTNode} node The node to report.
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* @returns {void}
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*/
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function report(node) {
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context.report({
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node,
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messageId: "unexpectedUndefined"
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});
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}
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/**
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* Checks the given scope for references to `undefined` and reports
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* all references found.
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* @param {eslint-scope.Scope} scope The scope to check.
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* @returns {void}
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*/
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function checkScope(scope) {
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const undefinedVar = scope.set.get("undefined");
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if (!undefinedVar) {
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return;
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}
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const references = undefinedVar.references;
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const defs = undefinedVar.defs;
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// Report non-initializing references (those are covered in defs below)
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references
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.filter(ref => !ref.init)
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.forEach(ref => report(ref.identifier));
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defs.forEach(def => report(def.name));
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}
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return {
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"Program:exit"() {
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const globalScope = context.getScope();
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const stack = [globalScope];
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while (stack.length) {
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const scope = stack.pop();
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stack.push(...scope.childScopes);
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checkScope(scope);
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}
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}
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};
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}
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};
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