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/**
* @fileoverview Rule to flag adding properties to native object's prototypes.
* @author David Nelson
*/
"use strict";
//------------------------------------------------------------------------------
// Requirements
//------------------------------------------------------------------------------
const globals = require("globals");
//------------------------------------------------------------------------------
// Rule Definition
//------------------------------------------------------------------------------
module.exports = {
meta: {
docs: {
description: "disallow extending native types",
category: "Best Practices",
recommended: false
},
schema: [
{
type: "object",
properties: {
exceptions: {
type: "array",
items: {
type: "string"
},
uniqueItems: true
}
},
additionalProperties: false
}
]
},
create(context) {
const config = context.options[0] || {};
const exceptions = config.exceptions || [];
let modifiedBuiltins = Object.keys(globals.builtin).filter(function(builtin) {
return builtin[0].toUpperCase() === builtin[0];
});
if (exceptions.length) {
modifiedBuiltins = modifiedBuiltins.filter(function(builtIn) {
return exceptions.indexOf(builtIn) === -1;
});
}
return {
// handle the Array.prototype.extra style case
AssignmentExpression(node) {
const lhs = node.left;
if (lhs.type !== "MemberExpression" || lhs.object.type !== "MemberExpression") {
return;
}
const affectsProto = lhs.object.computed ?
lhs.object.property.type === "Literal" && lhs.object.property.value === "prototype" :
lhs.object.property.name === "prototype";
if (!affectsProto) {
return;
}
modifiedBuiltins.forEach(function(builtin) {
if (lhs.object.object.name === builtin) {
context.report(node, builtin + " prototype is read only, properties should not be added.");
}
});
},
// handle the Object.definePropert[y|ies](Array.prototype) case
CallExpression(node) {
const callee = node.callee;
// only worry about Object.definePropert[y|ies]
if (callee.type === "MemberExpression" &&
callee.object.name === "Object" &&
(callee.property.name === "defineProperty" || callee.property.name === "defineProperties")) {
// verify the object being added to is a native prototype
const subject = node.arguments[0];
const object = subject && subject.object;
if (object &&
object.type === "Identifier" &&
(modifiedBuiltins.indexOf(object.name) > -1) &&
subject.property.name === "prototype") {
context.report(node, object.name + " prototype is read only, properties should not be added.");
}
}
}
};
}
};
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