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/**
* @fileoverview Rule to flag when the same variable is declared more then once.
* @author Ilya Volodin
*/
"use strict";
//------------------------------------------------------------------------------
// Rule Definition
//------------------------------------------------------------------------------
module.exports = {
meta: {
docs: {
description: "disallow variable redeclaration",
category: "Best Practices",
recommended: true
},
schema: [
{
type: "object",
properties: {
builtinGlobals: { type: "boolean" }
},
additionalProperties: false
}
]
},
create(context) {
const options = {
builtinGlobals: Boolean(context.options[0] && context.options[0].builtinGlobals)
};
/**
* Find variables in a given scope and flag redeclared ones.
* @param {Scope} scope - An escope scope object.
* @returns {void}
* @private
*/
function findVariablesInScope(scope) {
scope.variables.forEach(variable => {
const hasBuiltin = options.builtinGlobals && "writeable" in variable;
const count = (hasBuiltin ? 1 : 0) + variable.identifiers.length;
if (count >= 2) {
variable.identifiers.sort((a, b) => a.range[1] - b.range[1]);
for (let i = (hasBuiltin ? 0 : 1), l = variable.identifiers.length; i < l; i++) {
context.report({ node: variable.identifiers[i], message: "'{{a}}' is already defined.", data: { a: variable.name } });
}
}
});
}
/**
* Find variables in the current scope.
* @param {ASTNode} node - The Program node.
* @returns {void}
* @private
*/
function checkForGlobal(node) {
const scope = context.getScope(),
parserOptions = context.parserOptions,
ecmaFeatures = parserOptions.ecmaFeatures || {};
// Nodejs env or modules has a special scope.
if (ecmaFeatures.globalReturn || node.sourceType === "module") {
findVariablesInScope(scope.childScopes[0]);
} else {
findVariablesInScope(scope);
}
}
/**
* Find variables in the current scope.
* @returns {void}
* @private
*/
function checkForBlock() {
findVariablesInScope(context.getScope());
}
if (context.parserOptions.ecmaVersion >= 6) {
return {
Program: checkForGlobal,
BlockStatement: checkForBlock,
SwitchStatement: checkForBlock
};
}
return {
Program: checkForGlobal,
FunctionDeclaration: checkForBlock,
FunctionExpression: checkForBlock,
ArrowFunctionExpression: checkForBlock
};
}
};
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