718 lines
27 KiB
JavaScript
718 lines
27 KiB
JavaScript
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/**
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* @fileoverview Rule to flag declared but unused variables
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* @author Ilya Volodin
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*/
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"use strict";
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//------------------------------------------------------------------------------
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// Requirements
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//------------------------------------------------------------------------------
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const astUtils = require("./utils/ast-utils");
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//------------------------------------------------------------------------------
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// Typedefs
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//------------------------------------------------------------------------------
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/**
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* Bag of data used for formatting the `unusedVar` lint message.
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* @typedef {Object} UnusedVarMessageData
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* @property {string} varName The name of the unused var.
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* @property {'defined'|'assigned a value'} action Description of the vars state.
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* @property {string} additional Any additional info to be appended at the end.
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*/
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//------------------------------------------------------------------------------
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// Rule Definition
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//------------------------------------------------------------------------------
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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: "problem",
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docs: {
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description: "disallow unused variables",
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recommended: true,
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url: "https://eslint.org/docs/rules/no-unused-vars"
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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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enum: ["all", "local"]
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},
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{
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type: "object",
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properties: {
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vars: {
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enum: ["all", "local"]
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},
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varsIgnorePattern: {
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type: "string"
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},
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args: {
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enum: ["all", "after-used", "none"]
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},
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ignoreRestSiblings: {
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type: "boolean"
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},
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argsIgnorePattern: {
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type: "string"
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},
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caughtErrors: {
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enum: ["all", "none"]
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},
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caughtErrorsIgnorePattern: {
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type: "string"
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},
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destructuredArrayIgnorePattern: {
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type: "string"
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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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unusedVar: "'{{varName}}' is {{action}} but never used{{additional}}."
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}
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},
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create(context) {
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const sourceCode = context.getSourceCode();
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const REST_PROPERTY_TYPE = /^(?:RestElement|(?:Experimental)?RestProperty)$/u;
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const config = {
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vars: "all",
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args: "after-used",
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ignoreRestSiblings: false,
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caughtErrors: "none"
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};
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const firstOption = context.options[0];
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if (firstOption) {
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if (typeof firstOption === "string") {
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config.vars = firstOption;
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} else {
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config.vars = firstOption.vars || config.vars;
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config.args = firstOption.args || config.args;
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config.ignoreRestSiblings = firstOption.ignoreRestSiblings || config.ignoreRestSiblings;
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config.caughtErrors = firstOption.caughtErrors || config.caughtErrors;
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if (firstOption.varsIgnorePattern) {
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config.varsIgnorePattern = new RegExp(firstOption.varsIgnorePattern, "u");
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}
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if (firstOption.argsIgnorePattern) {
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config.argsIgnorePattern = new RegExp(firstOption.argsIgnorePattern, "u");
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}
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if (firstOption.caughtErrorsIgnorePattern) {
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config.caughtErrorsIgnorePattern = new RegExp(firstOption.caughtErrorsIgnorePattern, "u");
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}
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if (firstOption.destructuredArrayIgnorePattern) {
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config.destructuredArrayIgnorePattern = new RegExp(firstOption.destructuredArrayIgnorePattern, "u");
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}
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}
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}
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/**
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* Generates the message data about the variable being defined and unused,
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* including the ignore pattern if configured.
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* @param {Variable} unusedVar eslint-scope variable object.
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* @returns {UnusedVarMessageData} The message data to be used with this unused variable.
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*/
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function getDefinedMessageData(unusedVar) {
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const defType = unusedVar.defs && unusedVar.defs[0] && unusedVar.defs[0].type;
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let type;
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let pattern;
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if (defType === "CatchClause" && config.caughtErrorsIgnorePattern) {
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type = "args";
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pattern = config.caughtErrorsIgnorePattern.toString();
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} else if (defType === "Parameter" && config.argsIgnorePattern) {
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type = "args";
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pattern = config.argsIgnorePattern.toString();
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} else if (defType !== "Parameter" && config.varsIgnorePattern) {
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type = "vars";
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pattern = config.varsIgnorePattern.toString();
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}
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const additional = type ? `. Allowed unused ${type} must match ${pattern}` : "";
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return {
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varName: unusedVar.name,
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action: "defined",
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additional
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};
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}
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/**
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* Generate the warning message about the variable being
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* assigned and unused, including the ignore pattern if configured.
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* @param {Variable} unusedVar eslint-scope variable object.
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* @returns {UnusedVarMessageData} The message data to be used with this unused variable.
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*/
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function getAssignedMessageData(unusedVar) {
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const def = unusedVar.defs[0];
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let additional = "";
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if (config.destructuredArrayIgnorePattern && def && def.name.parent.type === "ArrayPattern") {
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additional = `. Allowed unused elements of array destructuring patterns must match ${config.destructuredArrayIgnorePattern.toString()}`;
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} else if (config.varsIgnorePattern) {
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additional = `. Allowed unused vars must match ${config.varsIgnorePattern.toString()}`;
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}
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return {
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varName: unusedVar.name,
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action: "assigned a value",
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additional
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};
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}
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//--------------------------------------------------------------------------
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// Helpers
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//--------------------------------------------------------------------------
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const STATEMENT_TYPE = /(?:Statement|Declaration)$/u;
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/**
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* Determines if a given variable is being exported from a module.
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* @param {Variable} variable eslint-scope variable object.
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* @returns {boolean} True if the variable is exported, false if not.
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* @private
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*/
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function isExported(variable) {
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const definition = variable.defs[0];
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if (definition) {
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let node = definition.node;
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if (node.type === "VariableDeclarator") {
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node = node.parent;
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} else if (definition.type === "Parameter") {
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return false;
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}
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return node.parent.type.indexOf("Export") === 0;
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}
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return false;
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}
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/**
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* Checks whether a node is a sibling of the rest property or not.
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* @param {ASTNode} node a node to check
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* @returns {boolean} True if the node is a sibling of the rest property, otherwise false.
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*/
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function hasRestSibling(node) {
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return node.type === "Property" &&
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node.parent.type === "ObjectPattern" &&
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REST_PROPERTY_TYPE.test(node.parent.properties[node.parent.properties.length - 1].type);
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}
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/**
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* Determines if a variable has a sibling rest property
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* @param {Variable} variable eslint-scope variable object.
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* @returns {boolean} True if the variable is exported, false if not.
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* @private
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*/
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function hasRestSpreadSibling(variable) {
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if (config.ignoreRestSiblings) {
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const hasRestSiblingDefinition = variable.defs.some(def => hasRestSibling(def.name.parent));
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const hasRestSiblingReference = variable.references.some(ref => hasRestSibling(ref.identifier.parent));
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return hasRestSiblingDefinition || hasRestSiblingReference;
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}
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return false;
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}
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/**
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* Determines if a reference is a read operation.
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* @param {Reference} ref An eslint-scope Reference
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* @returns {boolean} whether the given reference represents a read operation
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* @private
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*/
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function isReadRef(ref) {
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return ref.isRead();
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}
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/**
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* Determine if an identifier is referencing an enclosing function name.
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* @param {Reference} ref The reference to check.
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* @param {ASTNode[]} nodes The candidate function nodes.
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* @returns {boolean} True if it's a self-reference, false if not.
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* @private
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*/
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function isSelfReference(ref, nodes) {
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let scope = ref.from;
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while (scope) {
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if (nodes.includes(scope.block)) {
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return true;
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}
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scope = scope.upper;
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}
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return false;
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}
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/**
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* Gets a list of function definitions for a specified variable.
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* @param {Variable} variable eslint-scope variable object.
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* @returns {ASTNode[]} Function nodes.
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* @private
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*/
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function getFunctionDefinitions(variable) {
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const functionDefinitions = [];
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variable.defs.forEach(def => {
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const { type, node } = def;
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// FunctionDeclarations
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if (type === "FunctionName") {
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functionDefinitions.push(node);
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}
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// FunctionExpressions
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if (type === "Variable" && node.init &&
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(node.init.type === "FunctionExpression" || node.init.type === "ArrowFunctionExpression")) {
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functionDefinitions.push(node.init);
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}
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});
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return functionDefinitions;
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}
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/**
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* Checks the position of given nodes.
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* @param {ASTNode} inner A node which is expected as inside.
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* @param {ASTNode} outer A node which is expected as outside.
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* @returns {boolean} `true` if the `inner` node exists in the `outer` node.
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* @private
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*/
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function isInside(inner, outer) {
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return (
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inner.range[0] >= outer.range[0] &&
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inner.range[1] <= outer.range[1]
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);
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}
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/**
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* Checks whether a given node is unused expression or not.
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* @param {ASTNode} node The node itself
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* @returns {boolean} The node is an unused expression.
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* @private
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*/
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function isUnusedExpression(node) {
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const parent = node.parent;
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if (parent.type === "ExpressionStatement") {
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return true;
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}
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if (parent.type === "SequenceExpression") {
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const isLastExpression = parent.expressions[parent.expressions.length - 1] === node;
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if (!isLastExpression) {
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return true;
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}
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return isUnusedExpression(parent);
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}
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return false;
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}
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/**
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* If a given reference is left-hand side of an assignment, this gets
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* the right-hand side node of the assignment.
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*
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* In the following cases, this returns null.
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*
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* - The reference is not the LHS of an assignment expression.
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* - The reference is inside of a loop.
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* - The reference is inside of a function scope which is different from
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* the declaration.
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* @param {eslint-scope.Reference} ref A reference to check.
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* @param {ASTNode} prevRhsNode The previous RHS node.
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* @returns {ASTNode|null} The RHS node or null.
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* @private
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*/
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function getRhsNode(ref, prevRhsNode) {
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const id = ref.identifier;
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const parent = id.parent;
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const refScope = ref.from.variableScope;
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const varScope = ref.resolved.scope.variableScope;
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const canBeUsedLater = refScope !== varScope || astUtils.isInLoop(id);
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/*
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* Inherits the previous node if this reference is in the node.
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* This is for `a = a + a`-like code.
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*/
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if (prevRhsNode && isInside(id, prevRhsNode)) {
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return prevRhsNode;
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}
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if (parent.type === "AssignmentExpression" &&
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isUnusedExpression(parent) &&
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id === parent.left &&
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!canBeUsedLater
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) {
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return parent.right;
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}
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return null;
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}
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/**
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* Checks whether a given function node is stored to somewhere or not.
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* If the function node is stored, the function can be used later.
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* @param {ASTNode} funcNode A function node to check.
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* @param {ASTNode} rhsNode The RHS node of the previous assignment.
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* @returns {boolean} `true` if under the following conditions:
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* - the funcNode is assigned to a variable.
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* - the funcNode is bound as an argument of a function call.
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* - the function is bound to a property and the object satisfies above conditions.
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* @private
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*/
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function isStorableFunction(funcNode, rhsNode) {
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let node = funcNode;
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let parent = funcNode.parent;
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while (parent && isInside(parent, rhsNode)) {
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switch (parent.type) {
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case "SequenceExpression":
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if (parent.expressions[parent.expressions.length - 1] !== node) {
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return false;
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}
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break;
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case "CallExpression":
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case "NewExpression":
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return parent.callee !== node;
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|
|
case "AssignmentExpression":
|
||
|
|
case "TaggedTemplateExpression":
|
||
|
|
case "YieldExpression":
|
||
|
|
return true;
|
||
|
|
|
||
|
|
default:
|
||
|
|
if (STATEMENT_TYPE.test(parent.type)) {
|
||
|
|
|
||
|
|
/*
|
||
|
|
* If it encountered statements, this is a complex pattern.
|
||
|
|
* Since analyzing complex patterns is hard, this returns `true` to avoid false positive.
|
||
|
|
*/
|
||
|
|
return true;
|
||
|
|
}
|
||
|
|
}
|
||
|
|
|
||
|
|
node = parent;
|
||
|
|
parent = parent.parent;
|
||
|
|
}
|
||
|
|
|
||
|
|
return false;
|
||
|
|
}
|
||
|
|
|
||
|
|
/**
|
||
|
|
* Checks whether a given Identifier node exists inside of a function node which can be used later.
|
||
|
|
*
|
||
|
|
* "can be used later" means:
|
||
|
|
* - the function is assigned to a variable.
|
||
|
|
* - the function is bound to a property and the object can be used later.
|
||
|
|
* - the function is bound as an argument of a function call.
|
||
|
|
*
|
||
|
|
* If a reference exists in a function which can be used later, the reference is read when the function is called.
|
||
|
|
* @param {ASTNode} id An Identifier node to check.
|
||
|
|
* @param {ASTNode} rhsNode The RHS node of the previous assignment.
|
||
|
|
* @returns {boolean} `true` if the `id` node exists inside of a function node which can be used later.
|
||
|
|
* @private
|
||
|
|
*/
|
||
|
|
function isInsideOfStorableFunction(id, rhsNode) {
|
||
|
|
const funcNode = astUtils.getUpperFunction(id);
|
||
|
|
|
||
|
|
return (
|
||
|
|
funcNode &&
|
||
|
|
isInside(funcNode, rhsNode) &&
|
||
|
|
isStorableFunction(funcNode, rhsNode)
|
||
|
|
);
|
||
|
|
}
|
||
|
|
|
||
|
|
/**
|
||
|
|
* Checks whether a given reference is a read to update itself or not.
|
||
|
|
* @param {eslint-scope.Reference} ref A reference to check.
|
||
|
|
* @param {ASTNode} rhsNode The RHS node of the previous assignment.
|
||
|
|
* @returns {boolean} The reference is a read to update itself.
|
||
|
|
* @private
|
||
|
|
*/
|
||
|
|
function isReadForItself(ref, rhsNode) {
|
||
|
|
const id = ref.identifier;
|
||
|
|
const parent = id.parent;
|
||
|
|
|
||
|
|
return ref.isRead() && (
|
||
|
|
|
||
|
|
// self update. e.g. `a += 1`, `a++`
|
||
|
|
(
|
||
|
|
(
|
||
|
|
parent.type === "AssignmentExpression" &&
|
||
|
|
parent.left === id &&
|
||
|
|
isUnusedExpression(parent)
|
||
|
|
) ||
|
||
|
|
(
|
||
|
|
parent.type === "UpdateExpression" &&
|
||
|
|
isUnusedExpression(parent)
|
||
|
|
)
|
||
|
|
) ||
|
||
|
|
|
||
|
|
// in RHS of an assignment for itself. e.g. `a = a + 1`
|
||
|
|
(
|
||
|
|
rhsNode &&
|
||
|
|
isInside(id, rhsNode) &&
|
||
|
|
!isInsideOfStorableFunction(id, rhsNode)
|
||
|
|
)
|
||
|
|
);
|
||
|
|
}
|
||
|
|
|
||
|
|
/**
|
||
|
|
* Determine if an identifier is used either in for-in or for-of loops.
|
||
|
|
* @param {Reference} ref The reference to check.
|
||
|
|
* @returns {boolean} whether reference is used in the for-in loops
|
||
|
|
* @private
|
||
|
|
*/
|
||
|
|
function isForInOfRef(ref) {
|
||
|
|
let target = ref.identifier.parent;
|
||
|
|
|
||
|
|
|
||
|
|
// "for (var ...) { return; }"
|
||
|
|
if (target.type === "VariableDeclarator") {
|
||
|
|
target = target.parent.parent;
|
||
|
|
}
|
||
|
|
|
||
|
|
if (target.type !== "ForInStatement" && target.type !== "ForOfStatement") {
|
||
|
|
return false;
|
||
|
|
}
|
||
|
|
|
||
|
|
// "for (...) { return; }"
|
||
|
|
if (target.body.type === "BlockStatement") {
|
||
|
|
target = target.body.body[0];
|
||
|
|
|
||
|
|
// "for (...) return;"
|
||
|
|
} else {
|
||
|
|
target = target.body;
|
||
|
|
}
|
||
|
|
|
||
|
|
// For empty loop body
|
||
|
|
if (!target) {
|
||
|
|
return false;
|
||
|
|
}
|
||
|
|
|
||
|
|
return target.type === "ReturnStatement";
|
||
|
|
}
|
||
|
|
|
||
|
|
/**
|
||
|
|
* Determines if the variable is used.
|
||
|
|
* @param {Variable} variable The variable to check.
|
||
|
|
* @returns {boolean} True if the variable is used
|
||
|
|
* @private
|
||
|
|
*/
|
||
|
|
function isUsedVariable(variable) {
|
||
|
|
const functionNodes = getFunctionDefinitions(variable),
|
||
|
|
isFunctionDefinition = functionNodes.length > 0;
|
||
|
|
let rhsNode = null;
|
||
|
|
|
||
|
|
return variable.references.some(ref => {
|
||
|
|
if (isForInOfRef(ref)) {
|
||
|
|
return true;
|
||
|
|
}
|
||
|
|
|
||
|
|
const forItself = isReadForItself(ref, rhsNode);
|
||
|
|
|
||
|
|
rhsNode = getRhsNode(ref, rhsNode);
|
||
|
|
|
||
|
|
return (
|
||
|
|
isReadRef(ref) &&
|
||
|
|
!forItself &&
|
||
|
|
!(isFunctionDefinition && isSelfReference(ref, functionNodes))
|
||
|
|
);
|
||
|
|
});
|
||
|
|
}
|
||
|
|
|
||
|
|
/**
|
||
|
|
* Checks whether the given variable is after the last used parameter.
|
||
|
|
* @param {eslint-scope.Variable} variable The variable to check.
|
||
|
|
* @returns {boolean} `true` if the variable is defined after the last
|
||
|
|
* used parameter.
|
||
|
|
*/
|
||
|
|
function isAfterLastUsedArg(variable) {
|
||
|
|
const def = variable.defs[0];
|
||
|
|
const params = context.getDeclaredVariables(def.node);
|
||
|
|
const posteriorParams = params.slice(params.indexOf(variable) + 1);
|
||
|
|
|
||
|
|
// If any used parameters occur after this parameter, do not report.
|
||
|
|
return !posteriorParams.some(v => v.references.length > 0 || v.eslintUsed);
|
||
|
|
}
|
||
|
|
|
||
|
|
/**
|
||
|
|
* Gets an array of variables without read references.
|
||
|
|
* @param {Scope} scope an eslint-scope Scope object.
|
||
|
|
* @param {Variable[]} unusedVars an array that saving result.
|
||
|
|
* @returns {Variable[]} unused variables of the scope and descendant scopes.
|
||
|
|
* @private
|
||
|
|
*/
|
||
|
|
function collectUnusedVariables(scope, unusedVars) {
|
||
|
|
const variables = scope.variables;
|
||
|
|
const childScopes = scope.childScopes;
|
||
|
|
let i, l;
|
||
|
|
|
||
|
|
if (scope.type !== "global" || config.vars === "all") {
|
||
|
|
for (i = 0, l = variables.length; i < l; ++i) {
|
||
|
|
const variable = variables[i];
|
||
|
|
|
||
|
|
// skip a variable of class itself name in the class scope
|
||
|
|
if (scope.type === "class" && scope.block.id === variable.identifiers[0]) {
|
||
|
|
continue;
|
||
|
|
}
|
||
|
|
|
||
|
|
// skip function expression names and variables marked with markVariableAsUsed()
|
||
|
|
if (scope.functionExpressionScope || variable.eslintUsed) {
|
||
|
|
continue;
|
||
|
|
}
|
||
|
|
|
||
|
|
// skip implicit "arguments" variable
|
||
|
|
if (scope.type === "function" && variable.name === "arguments" && variable.identifiers.length === 0) {
|
||
|
|
continue;
|
||
|
|
}
|
||
|
|
|
||
|
|
// explicit global variables don't have definitions.
|
||
|
|
const def = variable.defs[0];
|
||
|
|
|
||
|
|
if (def) {
|
||
|
|
const type = def.type;
|
||
|
|
const refUsedInArrayPatterns = variable.references.some(ref => ref.identifier.parent.type === "ArrayPattern");
|
||
|
|
|
||
|
|
// skip elements of array destructuring patterns
|
||
|
|
if (
|
||
|
|
(
|
||
|
|
def.name.parent.type === "ArrayPattern" ||
|
||
|
|
refUsedInArrayPatterns
|
||
|
|
) &&
|
||
|
|
config.destructuredArrayIgnorePattern &&
|
||
|
|
config.destructuredArrayIgnorePattern.test(def.name.name)
|
||
|
|
) {
|
||
|
|
continue;
|
||
|
|
}
|
||
|
|
|
||
|
|
// skip catch variables
|
||
|
|
if (type === "CatchClause") {
|
||
|
|
if (config.caughtErrors === "none") {
|
||
|
|
continue;
|
||
|
|
}
|
||
|
|
|
||
|
|
// skip ignored parameters
|
||
|
|
if (config.caughtErrorsIgnorePattern && config.caughtErrorsIgnorePattern.test(def.name.name)) {
|
||
|
|
continue;
|
||
|
|
}
|
||
|
|
}
|
||
|
|
|
||
|
|
if (type === "Parameter") {
|
||
|
|
|
||
|
|
// skip any setter argument
|
||
|
|
if ((def.node.parent.type === "Property" || def.node.parent.type === "MethodDefinition") && def.node.parent.kind === "set") {
|
||
|
|
continue;
|
||
|
|
}
|
||
|
|
|
||
|
|
// if "args" option is "none", skip any parameter
|
||
|
|
if (config.args === "none") {
|
||
|
|
continue;
|
||
|
|
}
|
||
|
|
|
||
|
|
// skip ignored parameters
|
||
|
|
if (config.argsIgnorePattern && config.argsIgnorePattern.test(def.name.name)) {
|
||
|
|
continue;
|
||
|
|
}
|
||
|
|
|
||
|
|
// if "args" option is "after-used", skip used variables
|
||
|
|
if (config.args === "after-used" && astUtils.isFunction(def.name.parent) && !isAfterLastUsedArg(variable)) {
|
||
|
|
continue;
|
||
|
|
}
|
||
|
|
} else {
|
||
|
|
|
||
|
|
// skip ignored variables
|
||
|
|
if (config.varsIgnorePattern && config.varsIgnorePattern.test(def.name.name)) {
|
||
|
|
continue;
|
||
|
|
}
|
||
|
|
}
|
||
|
|
}
|
||
|
|
|
||
|
|
if (!isUsedVariable(variable) && !isExported(variable) && !hasRestSpreadSibling(variable)) {
|
||
|
|
unusedVars.push(variable);
|
||
|
|
}
|
||
|
|
}
|
||
|
|
}
|
||
|
|
|
||
|
|
for (i = 0, l = childScopes.length; i < l; ++i) {
|
||
|
|
collectUnusedVariables(childScopes[i], unusedVars);
|
||
|
|
}
|
||
|
|
|
||
|
|
return unusedVars;
|
||
|
|
}
|
||
|
|
|
||
|
|
//--------------------------------------------------------------------------
|
||
|
|
// Public
|
||
|
|
//--------------------------------------------------------------------------
|
||
|
|
|
||
|
|
return {
|
||
|
|
"Program:exit"(programNode) {
|
||
|
|
const unusedVars = collectUnusedVariables(context.getScope(), []);
|
||
|
|
|
||
|
|
for (let i = 0, l = unusedVars.length; i < l; ++i) {
|
||
|
|
const unusedVar = unusedVars[i];
|
||
|
|
|
||
|
|
// Report the first declaration.
|
||
|
|
if (unusedVar.defs.length > 0) {
|
||
|
|
|
||
|
|
// report last write reference, https://github.com/eslint/eslint/issues/14324
|
||
|
|
const writeReferences = unusedVar.references.filter(ref => ref.isWrite() && ref.from.variableScope === unusedVar.scope.variableScope);
|
||
|
|
|
||
|
|
let referenceToReport;
|
||
|
|
|
||
|
|
if (writeReferences.length > 0) {
|
||
|
|
referenceToReport = writeReferences[writeReferences.length - 1];
|
||
|
|
}
|
||
|
|
|
||
|
|
context.report({
|
||
|
|
node: referenceToReport ? referenceToReport.identifier : unusedVar.identifiers[0],
|
||
|
|
messageId: "unusedVar",
|
||
|
|
data: unusedVar.references.some(ref => ref.isWrite())
|
||
|
|
? getAssignedMessageData(unusedVar)
|
||
|
|
: getDefinedMessageData(unusedVar)
|
||
|
|
});
|
||
|
|
|
||
|
|
// If there are no regular declaration, report the first `/*globals*/` comment directive.
|
||
|
|
} else if (unusedVar.eslintExplicitGlobalComments) {
|
||
|
|
const directiveComment = unusedVar.eslintExplicitGlobalComments[0];
|
||
|
|
|
||
|
|
context.report({
|
||
|
|
node: programNode,
|
||
|
|
loc: astUtils.getNameLocationInGlobalDirectiveComment(sourceCode, directiveComment, unusedVar.name),
|
||
|
|
messageId: "unusedVar",
|
||
|
|
data: getDefinedMessageData(unusedVar)
|
||
|
|
});
|
||
|
|
}
|
||
|
|
}
|
||
|
|
}
|
||
|
|
};
|
||
|
|
|
||
|
|
}
|
||
|
|
};
|