225 lines
8 KiB
JavaScript
225 lines
8 KiB
JavaScript
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/**
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* @fileoverview Rule to flag on declaring variables already declared in the outer scope
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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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// Rule Definition
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//------------------------------------------------------------------------------
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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 variable declarations from shadowing variables declared in the outer scope",
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category: "Variables",
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recommended: false,
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url: "https://eslint.org/docs/rules/no-shadow"
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},
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schema: [
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{
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type: "object",
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properties: {
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builtinGlobals: { type: "boolean", default: false },
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hoist: { enum: ["all", "functions", "never"], default: "functions" },
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allow: {
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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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}
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},
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additionalProperties: false
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}
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],
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messages: {
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noShadow: "'{{name}}' is already declared in the upper scope on line {{shadowedLine}} column {{shadowedColumn}}.",
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noShadowGlobal: "'{{name}}' is already a global variable."
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}
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},
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create(context) {
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const options = {
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builtinGlobals: context.options[0] && context.options[0].builtinGlobals,
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hoist: (context.options[0] && context.options[0].hoist) || "functions",
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allow: (context.options[0] && context.options[0].allow) || []
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};
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/**
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* Check if variable name is allowed.
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* @param {ASTNode} variable The variable to check.
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* @returns {boolean} Whether or not the variable name is allowed.
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*/
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function isAllowed(variable) {
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return options.allow.indexOf(variable.name) !== -1;
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}
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/**
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* Checks if a variable of the class name in the class scope of ClassDeclaration.
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*
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* ClassDeclaration creates two variables of its name into its outer scope and its class scope.
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* So we should ignore the variable in the class scope.
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* @param {Object} variable The variable to check.
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* @returns {boolean} Whether or not the variable of the class name in the class scope of ClassDeclaration.
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*/
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function isDuplicatedClassNameVariable(variable) {
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const block = variable.scope.block;
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return block.type === "ClassDeclaration" && block.id === variable.identifiers[0];
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}
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/**
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* Checks if a variable is inside the initializer of scopeVar.
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*
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* To avoid reporting at declarations such as `var a = function a() {};`.
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* But it should report `var a = function(a) {};` or `var a = function() { function a() {} };`.
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* @param {Object} variable The variable to check.
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* @param {Object} scopeVar The scope variable to look for.
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* @returns {boolean} Whether or not the variable is inside initializer of scopeVar.
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*/
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function isOnInitializer(variable, scopeVar) {
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const outerScope = scopeVar.scope;
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const outerDef = scopeVar.defs[0];
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const outer = outerDef && outerDef.parent && outerDef.parent.range;
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const innerScope = variable.scope;
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const innerDef = variable.defs[0];
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const inner = innerDef && innerDef.name.range;
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return (
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outer &&
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inner &&
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outer[0] < inner[0] &&
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inner[1] < outer[1] &&
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((innerDef.type === "FunctionName" && innerDef.node.type === "FunctionExpression") || innerDef.node.type === "ClassExpression") &&
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outerScope === innerScope.upper
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);
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}
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/**
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* Get a range of a variable's identifier node.
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* @param {Object} variable The variable to get.
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* @returns {Array|undefined} The range of the variable's identifier node.
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*/
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function getNameRange(variable) {
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const def = variable.defs[0];
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return def && def.name.range;
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}
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/**
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* Get declared line and column of a variable.
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* @param {eslint-scope.Variable} variable The variable to get.
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* @returns {Object} The declared line and column of the variable.
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*/
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function getDeclaredLocation(variable) {
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const identifier = variable.identifiers[0];
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let obj;
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if (identifier) {
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obj = {
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global: false,
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line: identifier.loc.start.line,
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column: identifier.loc.start.column + 1
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};
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} else {
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obj = {
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global: true
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};
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}
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return obj;
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}
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/**
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* Checks if a variable is in TDZ of scopeVar.
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* @param {Object} variable The variable to check.
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* @param {Object} scopeVar The variable of TDZ.
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* @returns {boolean} Whether or not the variable is in TDZ of scopeVar.
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*/
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function isInTdz(variable, scopeVar) {
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const outerDef = scopeVar.defs[0];
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const inner = getNameRange(variable);
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const outer = getNameRange(scopeVar);
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return (
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inner &&
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outer &&
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inner[1] < outer[0] &&
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// Excepts FunctionDeclaration if is {"hoist":"function"}.
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(options.hoist !== "functions" || !outerDef || outerDef.node.type !== "FunctionDeclaration")
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);
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}
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/**
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* Checks the current context for shadowed variables.
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* @param {Scope} scope Fixme
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* @returns {void}
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*/
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function checkForShadows(scope) {
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const variables = scope.variables;
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for (let i = 0; i < variables.length; ++i) {
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const variable = variables[i];
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// Skips "arguments" or variables of a class name in the class scope of ClassDeclaration.
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if (variable.identifiers.length === 0 ||
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isDuplicatedClassNameVariable(variable) ||
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isAllowed(variable)
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) {
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continue;
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}
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// Gets shadowed variable.
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const shadowed = astUtils.getVariableByName(scope.upper, variable.name);
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if (shadowed &&
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(shadowed.identifiers.length > 0 || (options.builtinGlobals && "writeable" in shadowed)) &&
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!isOnInitializer(variable, shadowed) &&
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!(options.hoist !== "all" && isInTdz(variable, shadowed))
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) {
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const location = getDeclaredLocation(shadowed);
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const messageId = location.global ? "noShadowGlobal" : "noShadow";
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const data = { name: variable.name };
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if (!location.global) {
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data.shadowedLine = location.line;
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data.shadowedColumn = location.column;
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}
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context.report({
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node: variable.identifiers[0],
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messageId,
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data
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});
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}
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}
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}
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return {
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"Program:exit"() {
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const globalScope = context.getScope();
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const stack = globalScope.childScopes.slice();
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while (stack.length) {
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const scope = stack.pop();
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stack.push(...scope.childScopes);
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checkForShadows(scope);
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}
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}
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};
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}
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};
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