no-useless-computed-key.js
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/**
* @fileoverview Rule to disallow unnecessary computed property keys in object literals
* @author Burak Yigit Kaya
*/
"use strict";
//------------------------------------------------------------------------------
// Requirements
//------------------------------------------------------------------------------
const lodash = require("lodash");
const astUtils = require("./utils/ast-utils");
//------------------------------------------------------------------------------
// Rule Definition
//------------------------------------------------------------------------------
const MESSAGE_UNNECESSARY_COMPUTED = "Unnecessarily computed property [{{property}}] found.";
module.exports = {
meta: {
type: "suggestion",
docs: {
description: "disallow unnecessary computed property keys in objects and classes",
category: "ECMAScript 6",
recommended: false,
url: "https://eslint.org/docs/rules/no-useless-computed-key"
},
schema: [{
type: "object",
properties: {
enforceForClassMembers: {
type: "boolean",
default: false
}
},
additionalProperties: false
}],
fixable: "code"
},
create(context) {
const sourceCode = context.getSourceCode();
const enforceForClassMembers = context.options[0] && context.options[0].enforceForClassMembers;
/**
* Reports a given node if it violated this rule.
* @param {ASTNode} node The node to check.
* @returns {void}
*/
function check(node) {
if (!node.computed) {
return;
}
const key = node.key,
nodeType = typeof key.value;
let allowedKey;
if (node.type === "MethodDefinition") {
allowedKey = node.static ? "prototype" : "constructor";
} else {
allowedKey = "__proto__";
}
if (key.type === "Literal" && (nodeType === "string" || nodeType === "number") && key.value !== allowedKey) {
context.report({
node,
message: MESSAGE_UNNECESSARY_COMPUTED,
data: { property: sourceCode.getText(key) },
fix(fixer) {
const leftSquareBracket = sourceCode.getFirstToken(node, astUtils.isOpeningBracketToken);
const rightSquareBracket = sourceCode.getFirstTokenBetween(node.key, node.value, astUtils.isClosingBracketToken);
const tokensBetween = sourceCode.getTokensBetween(leftSquareBracket, rightSquareBracket, 1);
if (tokensBetween.slice(0, -1).some((token, index) =>
sourceCode.getText().slice(token.range[1], tokensBetween[index + 1].range[0]).trim())) {
// If there are comments between the brackets and the property name, don't do a fix.
return null;
}
const tokenBeforeLeftBracket = sourceCode.getTokenBefore(leftSquareBracket);
// Insert a space before the key to avoid changing identifiers, e.g. ({ get[2]() {} }) to ({ get2() {} })
const needsSpaceBeforeKey = tokenBeforeLeftBracket.range[1] === leftSquareBracket.range[0] &&
!astUtils.canTokensBeAdjacent(tokenBeforeLeftBracket, sourceCode.getFirstToken(key));
const replacementKey = (needsSpaceBeforeKey ? " " : "") + key.raw;
return fixer.replaceTextRange([leftSquareBracket.range[0], rightSquareBracket.range[1]], replacementKey);
}
});
}
}
return {
Property: check,
MethodDefinition: enforceForClassMembers ? check : lodash.noop
};
}
};