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/**
* @fileoverview Rule to flag when return statement contains assignment
* @author Ilya Volodin
*/
"use strict";
//------------------------------------------------------------------------------
// Helpers
//------------------------------------------------------------------------------
const SENTINEL_TYPE = /^(?:[a-zA-Z]+?Statement|ArrowFunctionExpression|FunctionExpression|ClassExpression)$/;
/**
* Checks whether or not a node is enclosed in parentheses.
* @param {Node|null} node - A node to check.
* @param {sourceCode} sourceCode - The ESLint SourceCode object.
* @returns {boolean} Whether or not the node is enclosed in parentheses.
*/
function isEnclosedInParens(node, sourceCode) {
const prevToken = sourceCode.getTokenBefore(node);
const nextToken = sourceCode.getTokenAfter(node);
return prevToken && prevToken.value === "(" && nextToken && nextToken.value === ")";
}
//------------------------------------------------------------------------------
// Rule Definition
//------------------------------------------------------------------------------
module.exports = {
meta: {
docs: {
description: "disallow assignment operators in `return` statements",
category: "Best Practices",
recommended: false
},
schema: [
{
enum: ["except-parens", "always"]
}
]
},
create(context) {
const always = (context.options[0] || "except-parens") !== "except-parens";
const sourceCode = context.getSourceCode();
return {
AssignmentExpression(node) {
if (!always && isEnclosedInParens(node, sourceCode)) {
return;
}
let parent = node.parent;
// Find ReturnStatement or ArrowFunctionExpression in ancestors.
while (parent && !SENTINEL_TYPE.test(parent.type)) {
node = parent;
parent = parent.parent;
}
// Reports.
if (parent && parent.type === "ReturnStatement") {
context.report({
node: parent,
message: "Return statement should not contain assignment."
});
} else if (parent && parent.type === "ArrowFunctionExpression" && parent.body === node) {
context.report({
node: parent,
message: "Arrow function should not return assignment."
});
}
}
};
}
};
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