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230 lines
8.4 KiB
230 lines
8.4 KiB
/**
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* @fileoverview Disallow reassignment of function parameters.
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* @author Nat Burns
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*/
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"use strict";
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//------------------------------------------------------------------------------
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// Rule Definition
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//------------------------------------------------------------------------------
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const stopNodePattern = /(?:Statement|Declaration|Function(?:Expression)?|Program)$/u;
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/** @type {import('../shared/types').Rule} */
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module.exports = {
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meta: {
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type: "suggestion",
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docs: {
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description: "Disallow reassigning `function` parameters",
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recommended: false,
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url: "https://eslint.org/docs/latest/rules/no-param-reassign"
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},
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schema: [
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{
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oneOf: [
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{
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type: "object",
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properties: {
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props: {
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enum: [false]
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}
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},
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additionalProperties: false
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},
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{
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type: "object",
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properties: {
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props: {
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enum: [true]
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},
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ignorePropertyModificationsFor: {
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type: "array",
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items: {
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type: "string"
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},
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uniqueItems: true
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},
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ignorePropertyModificationsForRegex: {
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type: "array",
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items: {
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type: "string"
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},
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uniqueItems: true
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}
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},
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additionalProperties: false
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}
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]
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}
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],
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messages: {
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assignmentToFunctionParam: "Assignment to function parameter '{{name}}'.",
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assignmentToFunctionParamProp: "Assignment to property of function parameter '{{name}}'."
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}
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},
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create(context) {
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const props = context.options[0] && context.options[0].props;
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const ignoredPropertyAssignmentsFor = context.options[0] && context.options[0].ignorePropertyModificationsFor || [];
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const ignoredPropertyAssignmentsForRegex = context.options[0] && context.options[0].ignorePropertyModificationsForRegex || [];
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const sourceCode = context.sourceCode;
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/**
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* Checks whether or not the reference modifies properties of its variable.
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* @param {Reference} reference A reference to check.
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* @returns {boolean} Whether or not the reference modifies properties of its variable.
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*/
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function isModifyingProp(reference) {
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let node = reference.identifier;
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let parent = node.parent;
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while (parent && (!stopNodePattern.test(parent.type) ||
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parent.type === "ForInStatement" || parent.type === "ForOfStatement")) {
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switch (parent.type) {
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// e.g. foo.a = 0;
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case "AssignmentExpression":
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return parent.left === node;
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// e.g. ++foo.a;
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case "UpdateExpression":
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return true;
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// e.g. delete foo.a;
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case "UnaryExpression":
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if (parent.operator === "delete") {
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return true;
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}
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break;
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// e.g. for (foo.a in b) {}
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case "ForInStatement":
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case "ForOfStatement":
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if (parent.left === node) {
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return true;
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}
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// this is a stop node for parent.right and parent.body
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return false;
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// EXCLUDES: e.g. cache.get(foo.a).b = 0;
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case "CallExpression":
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if (parent.callee !== node) {
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return false;
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}
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break;
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// EXCLUDES: e.g. cache[foo.a] = 0;
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case "MemberExpression":
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if (parent.property === node) {
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return false;
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}
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break;
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// EXCLUDES: e.g. ({ [foo]: a }) = bar;
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case "Property":
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if (parent.key === node) {
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return false;
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}
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break;
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// EXCLUDES: e.g. (foo ? a : b).c = bar;
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case "ConditionalExpression":
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if (parent.test === node) {
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return false;
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}
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break;
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// no default
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}
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node = parent;
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parent = node.parent;
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}
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return false;
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}
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/**
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* Tests that an identifier name matches any of the ignored property assignments.
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* First we test strings in ignoredPropertyAssignmentsFor.
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* Then we instantiate and test RegExp objects from ignoredPropertyAssignmentsForRegex strings.
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* @param {string} identifierName A string that describes the name of an identifier to
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* ignore property assignments for.
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* @returns {boolean} Whether the string matches an ignored property assignment regular expression or not.
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*/
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function isIgnoredPropertyAssignment(identifierName) {
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return ignoredPropertyAssignmentsFor.includes(identifierName) ||
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ignoredPropertyAssignmentsForRegex.some(ignored => new RegExp(ignored, "u").test(identifierName));
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}
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/**
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* Reports a reference if is non initializer and writable.
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* @param {Reference} reference A reference to check.
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* @param {int} index The index of the reference in the references.
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* @param {Reference[]} references The array that the reference belongs to.
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* @returns {void}
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*/
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function checkReference(reference, index, references) {
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const identifier = reference.identifier;
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if (identifier &&
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!reference.init &&
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/*
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* Destructuring assignments can have multiple default value,
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* so possibly there are multiple writeable references for the same identifier.
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*/
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(index === 0 || references[index - 1].identifier !== identifier)
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) {
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if (reference.isWrite()) {
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context.report({
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node: identifier,
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messageId: "assignmentToFunctionParam",
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data: { name: identifier.name }
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});
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} else if (props && isModifyingProp(reference) && !isIgnoredPropertyAssignment(identifier.name)) {
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context.report({
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node: identifier,
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messageId: "assignmentToFunctionParamProp",
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data: { name: identifier.name }
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});
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}
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}
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}
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/**
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* Finds and reports references that are non initializer and writable.
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* @param {Variable} variable A variable to check.
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* @returns {void}
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*/
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function checkVariable(variable) {
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if (variable.defs[0].type === "Parameter") {
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variable.references.forEach(checkReference);
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}
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}
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/**
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* Checks parameters of a given function node.
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* @param {ASTNode} node A function node to check.
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* @returns {void}
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*/
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function checkForFunction(node) {
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sourceCode.getDeclaredVariables(node).forEach(checkVariable);
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}
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return {
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// `:exit` is needed for the `node.parent` property of identifier nodes.
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"FunctionDeclaration:exit": checkForFunction,
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"FunctionExpression:exit": checkForFunction,
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"ArrowFunctionExpression:exit": checkForFunction
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};
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}
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};
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