Current File : /var/www/html/node_modules/eslint/lib/rules/no-useless-computed-key.js
/**
* @fileoverview Rule to disallow unnecessary computed property keys in object literals
* @author Burak Yigit Kaya
*/
"use strict";
//------------------------------------------------------------------------------
// Requirements
//------------------------------------------------------------------------------
const astUtils = require("./utils/ast-utils");
//------------------------------------------------------------------------------
// Helpers
//------------------------------------------------------------------------------
/**
* Determines whether the computed key syntax is unnecessarily used for the given node.
* In particular, it determines whether removing the square brackets and using the content between them
* directly as the key (e.g. ['foo'] -> 'foo') would produce valid syntax and preserve the same behavior.
* Valid non-computed keys are only: identifiers, number literals and string literals.
* Only literals can preserve the same behavior, with a few exceptions for specific node types:
* Property
* - { ["__proto__"]: foo } defines a property named "__proto__"
* { "__proto__": foo } defines object's prototype
* PropertyDefinition
* - class C { ["constructor"]; } defines an instance field named "constructor"
* class C { "constructor"; } produces a parsing error
* - class C { static ["constructor"]; } defines a static field named "constructor"
* class C { static "constructor"; } produces a parsing error
* - class C { static ["prototype"]; } produces a runtime error (doesn't break the whole script)
* class C { static "prototype"; } produces a parsing error (breaks the whole script)
* MethodDefinition
* - class C { ["constructor"]() {} } defines a prototype method named "constructor"
* class C { "constructor"() {} } defines the constructor
* - class C { static ["prototype"]() {} } produces a runtime error (doesn't break the whole script)
* class C { static "prototype"() {} } produces a parsing error (breaks the whole script)
* @param {ASTNode} node The node to check. It can be `Property`, `PropertyDefinition` or `MethodDefinition`.
* @throws {Error} (Unreachable.)
* @returns {void} `true` if the node has useless computed key.
*/
function hasUselessComputedKey(node) {
if (!node.computed) {
return false;
}
const { key } = node;
if (key.type !== "Literal") {
return false;
}
const { value } = key;
if (typeof value !== "number" && typeof value !== "string") {
return false;
}
switch (node.type) {
case "Property":
return value !== "__proto__";
case "PropertyDefinition":
if (node.static) {
return value !== "constructor" && value !== "prototype";
}
return value !== "constructor";
case "MethodDefinition":
if (node.static) {
return value !== "prototype";
}
return value !== "constructor";
/* istanbul ignore next */
default:
throw new Error(`Unexpected node type: ${node.type}`);
}
}
//------------------------------------------------------------------------------
// Rule Definition
//------------------------------------------------------------------------------
/** @type {import('../shared/types').Rule} */
module.exports = {
meta: {
type: "suggestion",
docs: {
description: "disallow unnecessary computed property keys in objects and classes",
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",
messages: {
unnecessarilyComputedProperty: "Unnecessarily computed property [{{property}}] found."
}
},
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 (hasUselessComputedKey(node)) {
const { key } = node;
context.report({
node,
messageId: "unnecessarilyComputedProperty",
data: { property: sourceCode.getText(key) },
fix(fixer) {
const leftSquareBracket = sourceCode.getTokenBefore(key, astUtils.isOpeningBracketToken);
const rightSquareBracket = sourceCode.getTokenAfter(key, astUtils.isClosingBracketToken);
// If there are comments between the brackets and the property name, don't do a fix.
if (sourceCode.commentsExistBetween(leftSquareBracket, rightSquareBracket)) {
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);
}
});
}
}
/**
* A no-op function to act as placeholder for checking a node when the `enforceForClassMembers` option is `false`.
* @returns {void}
* @private
*/
function noop() {}
return {
Property: check,
MethodDefinition: enforceForClassMembers ? check : noop,
PropertyDefinition: enforceForClassMembers ? check : noop
};
}
};
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