1 | /**
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2 | * @fileoverview Rule to disallow assignments to native objects or read-only global variables
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3 | * @author Ilya Volodin
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4 | */
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5 |
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6 | "use strict";
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7 |
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8 | //------------------------------------------------------------------------------
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9 | // Rule Definition
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10 | //------------------------------------------------------------------------------
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11 |
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12 | /** @type {import('../shared/types').Rule} */
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13 | module.exports = {
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14 | meta: {
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15 | type: "suggestion",
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16 |
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17 | docs: {
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18 | description: "Disallow assignments to native objects or read-only global variables",
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19 | recommended: true,
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20 | url: "https://eslint.org/docs/latest/rules/no-global-assign"
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21 | },
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22 |
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23 | schema: [
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24 | {
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25 | type: "object",
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26 | properties: {
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27 | exceptions: {
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28 | type: "array",
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29 | items: { type: "string" },
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30 | uniqueItems: true
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31 | }
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32 | },
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33 | additionalProperties: false
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34 | }
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35 | ],
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36 |
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37 | messages: {
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38 | globalShouldNotBeModified: "Read-only global '{{name}}' should not be modified."
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39 | }
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40 | },
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41 |
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42 | create(context) {
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43 | const config = context.options[0];
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44 | const sourceCode = context.sourceCode;
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45 | const exceptions = (config && config.exceptions) || [];
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46 |
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47 | /**
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48 | * Reports write references.
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49 | * @param {Reference} reference A reference to check.
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50 | * @param {int} index The index of the reference in the references.
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51 | * @param {Reference[]} references The array that the reference belongs to.
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52 | * @returns {void}
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53 | */
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54 | function checkReference(reference, index, references) {
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55 | const identifier = reference.identifier;
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56 |
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57 | if (reference.init === false &&
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58 | reference.isWrite() &&
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59 |
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60 | /*
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61 | * Destructuring assignments can have multiple default value,
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62 | * so possibly there are multiple writeable references for the same identifier.
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63 | */
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64 | (index === 0 || references[index - 1].identifier !== identifier)
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65 | ) {
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66 | context.report({
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67 | node: identifier,
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68 | messageId: "globalShouldNotBeModified",
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69 | data: {
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70 | name: identifier.name
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71 | }
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72 | });
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73 | }
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74 | }
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75 |
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76 | /**
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77 | * Reports write references if a given variable is read-only builtin.
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78 | * @param {Variable} variable A variable to check.
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79 | * @returns {void}
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80 | */
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81 | function checkVariable(variable) {
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82 | if (variable.writeable === false && !exceptions.includes(variable.name)) {
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83 | variable.references.forEach(checkReference);
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84 | }
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85 | }
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86 |
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87 | return {
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88 | Program(node) {
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89 | const globalScope = sourceCode.getScope(node);
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90 |
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91 | globalScope.variables.forEach(checkVariable);
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92 | }
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93 | };
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94 | }
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95 | };
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