eslint/lib/rules/no-import-assign.js

   1 /**
   2  * @fileoverview Rule to flag updates of imported bindings.
   3  * @author Toru Nagashima <https://github.com/mysticatea>
   4  */
   5
   6 "use strict";
   7
   8 //------------------------------------------------------------------------------
   9 // Helpers
  10 //------------------------------------------------------------------------------
  11
  12 const { findVariable } = require("eslint-utils");
  13 const astUtils = require("./utils/ast-utils");
  14
  15 const WellKnownMutationFunctions = {
  16     Object: /^(?:assign|definePropert(?:y|ies)|freeze|setPrototypeOf)$/u,
  17     Reflect: /^(?:(?:define|delete)Property|set(?:PrototypeOf)?)$/u
  18 };
  19
  20 /**
  21  * Check if a given node is LHS of an assignment node.
  22  * @param {ASTNode} node The node to check.
  23  * @returns {boolean} `true` if the node is LHS.
  24  */
  25 function isAssignmentLeft(node) {
  26     const { parent } = node;
  27
  28     return (
  29         (
  30             parent.type === "AssignmentExpression" &&
  31             parent.left === node
  32         ) ||
  33
  34         // Destructuring assignments
  35         parent.type === "ArrayPattern" ||
  36         (
  37             parent.type === "Property" &&
  38             parent.value === node &&
  39             parent.parent.type === "ObjectPattern"
  40         ) ||
  41         parent.type === "RestElement" ||
  42         (
  43             parent.type === "AssignmentPattern" &&
  44             parent.left === node
  45         )
  46     );
  47 }
  48
  49 /**
  50  * Check if a given node is the operand of mutation unary operator.
  51  * @param {ASTNode} node The node to check.
  52  * @returns {boolean} `true` if the node is the operand of mutation unary operator.
  53  */
  54 function isOperandOfMutationUnaryOperator(node) {
  55     const argumentNode = node.parent.type === "ChainExpression"
  56         ? node.parent
  57         : node;
  58     const { parent } = argumentNode;
  59
  60     return (
  61         (
  62             parent.type === "UpdateExpression" &&
  63             parent.argument === argumentNode
  64         ) ||
  65         (
  66             parent.type === "UnaryExpression" &&
  67             parent.operator === "delete" &&
  68             parent.argument === argumentNode
  69         )
  70     );
  71 }
  72
  73 /**
  74  * Check if a given node is the iteration variable of `for-in`/`for-of` syntax.
  75  * @param {ASTNode} node The node to check.
  76  * @returns {boolean} `true` if the node is the iteration variable.
  77  */
  78 function isIterationVariable(node) {
  79     const { parent } = node;
  80
  81     return (
  82         (
  83             parent.type === "ForInStatement" &&
  84             parent.left === node
  85         ) ||
  86         (
  87             parent.type === "ForOfStatement" &&
  88             parent.left === node
  89         )
  90     );
  91 }
  92
  93 /**
  94  * Check if a given node is at the first argument of a well-known mutation function.
  95  * - `Object.assign`
  96  * - `Object.defineProperty`
  97  * - `Object.defineProperties`
  98  * - `Object.freeze`
  99  * - `Object.setPrototypeOf`
 100  * - `Reflect.defineProperty`
 101  * - `Reflect.deleteProperty`
 102  * - `Reflect.set`
 103  * - `Reflect.setPrototypeOf`
 104  * @param {ASTNode} node The node to check.
 105  * @param {Scope} scope A `escope.Scope` object to find variable (whichever).
 106  * @returns {boolean} `true` if the node is at the first argument of a well-known mutation function.
 107  */
 108 function isArgumentOfWellKnownMutationFunction(node, scope) {
 109     const { parent } = node;
 110
 111     if (parent.type !== "CallExpression" || parent.arguments[0] !== node) {
 112         return false;
 113     }
 114     const callee = astUtils.skipChainExpression(parent.callee);
 115
 116     if (
 117         !astUtils.isSpecificMemberAccess(callee, "Object", WellKnownMutationFunctions.Object) &&
 118         !astUtils.isSpecificMemberAccess(callee, "Reflect", WellKnownMutationFunctions.Reflect)
 119     ) {
 120         return false;
 121     }
 122     const variable = findVariable(scope, callee.object);
 123
 124     return variable !== null && variable.scope.type === "global";
 125 }
 126
 127 /**
 128  * Check if the identifier node is placed at to update members.
 129  * @param {ASTNode} id The Identifier node to check.
 130  * @param {Scope} scope A `escope.Scope` object to find variable (whichever).
 131  * @returns {boolean} `true` if the member of `id` was updated.
 132  */
 133 function isMemberWrite(id, scope) {
 134     const { parent } = id;
 135
 136     return (
 137         (
 138             parent.type === "MemberExpression" &&
 139             parent.object === id &&
 140             (
 141                 isAssignmentLeft(parent) ||
 142                 isOperandOfMutationUnaryOperator(parent) ||
 143                 isIterationVariable(parent)
 144             )
 145         ) ||
 146         isArgumentOfWellKnownMutationFunction(id, scope)
 147     );
 148 }
 149
 150 /**
 151  * Get the mutation node.
 152  * @param {ASTNode} id The Identifier node to get.
 153  * @returns {ASTNode} The mutation node.
 154  */
 155 function getWriteNode(id) {
 156     let node = id.parent;
 157
 158     while (
 159         node &&
 160         node.type !== "AssignmentExpression" &&
 161         node.type !== "UpdateExpression" &&
 162         node.type !== "UnaryExpression" &&
 163         node.type !== "CallExpression" &&
 164         node.type !== "ForInStatement" &&
 165         node.type !== "ForOfStatement"
 166     ) {
 167         node = node.parent;
 168     }
 169
 170     return node || id;
 171 }
 172
 173 //------------------------------------------------------------------------------
 174 // Rule Definition
 175 //------------------------------------------------------------------------------
 176
 177 /** @type {import('../shared/types').Rule} */
 178 module.exports = {
 179     meta: {
 180         type: "problem",
 181
 182         docs: {
 183             description: "disallow assigning to imported bindings",
 184             recommended: true,
 185             url: "https://eslint.org/docs/rules/no-import-assign"
 186         },
 187
 188         schema: [],
 189
 190         messages: {
 191             readonly: "'{{name}}' is read-only.",
 192             readonlyMember: "The members of '{{name}}' are read-only."
 193         }
 194     },
 195
 196     create(context) {
 197         return {
 198             ImportDeclaration(node) {
 199                 const scope = context.getScope();
 200
 201                 for (const variable of context.getDeclaredVariables(node)) {
 202                     const shouldCheckMembers = variable.defs.some(
 203                         d => d.node.type === "ImportNamespaceSpecifier"
 204                     );
 205                     let prevIdNode = null;
 206
 207                     for (const reference of variable.references) {
 208                         const idNode = reference.identifier;
 209
 210                         /*
 211                          * AssignmentPattern (e.g. `[a = 0] = b`) makes two write
 212                          * references for the same identifier. This should skip
 213                          * the one of the two in order to prevent redundant reports.
 214                          */
 215                         if (idNode === prevIdNode) {
 216                             continue;
 217                         }
 218                         prevIdNode = idNode;
 219
 220                         if (reference.isWrite()) {
 221                             context.report({
 222                                 node: getWriteNode(idNode),
 223                                 messageId: "readonly",
 224                                 data: { name: idNode.name }
 225                             });
 226                         } else if (shouldCheckMembers && isMemberWrite(idNode, scope)) {
 227                             context.report({
 228                                 node: getWriteNode(idNode),
 229                                 messageId: "readonlyMember",
 230                                 data: { name: idNode.name }
 231                             });
 232                         }
 233                     }
 234                 }
 235             }
 236         };
 237
 238     }
 239 };