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/**
* @fileoverview Rule to flag on declaring variables already declared in the outer scope
* @author Ilya Volodin
*/
"use strict";
//------------------------------------------------------------------------------
// Requirements
//------------------------------------------------------------------------------
const astUtils = require("./utils/ast-utils");
//------------------------------------------------------------------------------
// Helpers
//------------------------------------------------------------------------------
const FUNC_EXPR_NODE_TYPES = new Set(["ArrowFunctionExpression", "FunctionExpression"]);
const CALL_EXPR_NODE_TYPE = new Set(["CallExpression"]);
const FOR_IN_OF_TYPE = /^For(?:In|Of)Statement$/u;
const SENTINEL_TYPE = /^(?:(?:Function|Class)(?:Declaration|Expression)|ArrowFunctionExpression|CatchClause|ImportDeclaration|ExportNamedDeclaration)$/u;
//------------------------------------------------------------------------------
// Rule Definition
//------------------------------------------------------------------------------
/** @type {import('../shared/types').Rule} */
module.exports = {
meta: {
type: "suggestion",
docs: {
description: "Disallow variable declarations from shadowing variables declared in the outer scope",
recommended: false,
url: "https://eslint.org/docs/latest/rules/no-shadow"
},
schema: [
{
type: "object",
properties: {
builtinGlobals: { type: "boolean", default: false },
hoist: { enum: ["all", "functions", "never"], default: "functions" },
allow: {
type: "array",
items: {
type: "string"
}
},
ignoreOnInitialization: { type: "boolean", default: false }
},
additionalProperties: false
}
],
messages: {
noShadow: "'{{name}}' is already declared in the upper scope on line {{shadowedLine}} column {{shadowedColumn}}.",
noShadowGlobal: "'{{name}}' is already a global variable."
}
},
create(context) {
const options = {
builtinGlobals: context.options[0] && context.options[0].builtinGlobals,
hoist: (context.options[0] && context.options[0].hoist) || "functions",
allow: (context.options[0] && context.options[0].allow) || [],
ignoreOnInitialization: context.options[0] && context.options[0].ignoreOnInitialization
};
const sourceCode = context.sourceCode;
/**
* Checks whether or not a given location is inside of the range of a given node.
* @param {ASTNode} node An node to check.
* @param {number} location A location to check.
* @returns {boolean} `true` if the location is inside of the range of the node.
*/
function isInRange(node, location) {
return node && node.range[0] <= location && location <= node.range[1];
}
/**
* Searches from the current node through its ancestry to find a matching node.
* @param {ASTNode} node a node to get.
* @param {(node: ASTNode) => boolean} match a callback that checks whether or not the node verifies its condition or not.
* @returns {ASTNode|null} the matching node.
*/
function findSelfOrAncestor(node, match) {
let currentNode = node;
while (currentNode && !match(currentNode)) {
currentNode = currentNode.parent;
}
return currentNode;
}
/**
* Finds function's outer scope.
* @param {Scope} scope Function's own scope.
* @returns {Scope} Function's outer scope.
*/
function getOuterScope(scope) {
const upper = scope.upper;
if (upper.type === "function-expression-name") {
return upper.upper;
}
return upper;
}
/**
* Checks if a variable and a shadowedVariable have the same init pattern ancestor.
* @param {Object} variable a variable to check.
* @param {Object} shadowedVariable a shadowedVariable to check.
* @returns {boolean} Whether or not the variable and the shadowedVariable have the same init pattern ancestor.
*/
function isInitPatternNode(variable, shadowedVariable) {
const outerDef = shadowedVariable.defs[0];
if (!outerDef) {
return false;
}
const { variableScope } = variable.scope;
if (!(FUNC_EXPR_NODE_TYPES.has(variableScope.block.type) && getOuterScope(variableScope) === shadowedVariable.scope)) {
return false;
}
const fun = variableScope.block;
const { parent } = fun;
const callExpression = findSelfOrAncestor(
parent,
node => CALL_EXPR_NODE_TYPE.has(node.type)
);
if (!callExpression) {
return false;
}
let node = outerDef.name;
const location = callExpression.range[1];
while (node) {
if (node.type === "VariableDeclarator") {
if (isInRange(node.init, location)) {
return true;
}
if (FOR_IN_OF_TYPE.test(node.parent.parent.type) &&
isInRange(node.parent.parent.right, location)
) {
return true;
}
break;
} else if (node.type === "AssignmentPattern") {
if (isInRange(node.right, location)) {
return true;
}
} else if (SENTINEL_TYPE.test(node.type)) {
break;
}
node = node.parent;
}
return false;
}
/**
* Check if variable name is allowed.
* @param {ASTNode} variable The variable to check.
* @returns {boolean} Whether or not the variable name is allowed.
*/
function isAllowed(variable) {
return options.allow.includes(variable.name);
}
/**
* Checks if a variable of the class name in the class scope of ClassDeclaration.
*
* ClassDeclaration creates two variables of its name into its outer scope and its class scope.
* So we should ignore the variable in the class scope.
* @param {Object} variable The variable to check.
* @returns {boolean} Whether or not the variable of the class name in the class scope of ClassDeclaration.
*/
function isDuplicatedClassNameVariable(variable) {
const block = variable.scope.block;
return block.type === "ClassDeclaration" && block.id === variable.identifiers[0];
}
/**
* Checks if a variable is inside the initializer of scopeVar.
*
* To avoid reporting at declarations such as `var a = function a() {};`.
* But it should report `var a = function(a) {};` or `var a = function() { function a() {} };`.
* @param {Object} variable The variable to check.
* @param {Object} scopeVar The scope variable to look for.
* @returns {boolean} Whether or not the variable is inside initializer of scopeVar.
*/
function isOnInitializer(variable, scopeVar) {
const outerScope = scopeVar.scope;
const outerDef = scopeVar.defs[0];
const outer = outerDef && outerDef.parent && outerDef.parent.range;
const innerScope = variable.scope;
const innerDef = variable.defs[0];
const inner = innerDef && innerDef.name.range;
return (
outer &&
inner &&
outer[0] < inner[0] &&
inner[1] < outer[1] &&
((innerDef.type === "FunctionName" && innerDef.node.type === "FunctionExpression") || innerDef.node.type === "ClassExpression") &&
outerScope === innerScope.upper
);
}
/**
* Get a range of a variable's identifier node.
* @param {Object} variable The variable to get.
* @returns {Array|undefined} The range of the variable's identifier node.
*/
function getNameRange(variable) {
const def = variable.defs[0];
return def && def.name.range;
}
/**
* Get declared line and column of a variable.
* @param {eslint-scope.Variable} variable The variable to get.
* @returns {Object} The declared line and column of the variable.
*/
function getDeclaredLocation(variable) {
const identifier = variable.identifiers[0];
let obj;
if (identifier) {
obj = {
global: false,
line: identifier.loc.start.line,
column: identifier.loc.start.column + 1
};
} else {
obj = {
global: true
};
}
return obj;
}
/**
* Checks if a variable is in TDZ of scopeVar.
* @param {Object} variable The variable to check.
* @param {Object} scopeVar The variable of TDZ.
* @returns {boolean} Whether or not the variable is in TDZ of scopeVar.
*/
function isInTdz(variable, scopeVar) {
const outerDef = scopeVar.defs[0];
const inner = getNameRange(variable);
const outer = getNameRange(scopeVar);
return (
inner &&
outer &&
inner[1] < outer[0] &&
// Excepts FunctionDeclaration if is {"hoist":"function"}.
(options.hoist !== "functions" || !outerDef || outerDef.node.type !== "FunctionDeclaration")
);
}
/**
* Checks the current context for shadowed variables.
* @param {Scope} scope Fixme
* @returns {void}
*/
function checkForShadows(scope) {
const variables = scope.variables;
for (let i = 0; i < variables.length; ++i) {
const variable = variables[i];
// Skips "arguments" or variables of a class name in the class scope of ClassDeclaration.
if (variable.identifiers.length === 0 ||
isDuplicatedClassNameVariable(variable) ||
isAllowed(variable)
) {
continue;
}
// Gets shadowed variable.
const shadowed = astUtils.getVariableByName(scope.upper, variable.name);
if (shadowed &&
(shadowed.identifiers.length > 0 || (options.builtinGlobals && "writeable" in shadowed)) &&
!isOnInitializer(variable, shadowed) &&
!(options.ignoreOnInitialization && isInitPatternNode(variable, shadowed)) &&
!(options.hoist !== "all" && isInTdz(variable, shadowed))
) {
const location = getDeclaredLocation(shadowed);
const messageId = location.global ? "noShadowGlobal" : "noShadow";
const data = { name: variable.name };
if (!location.global) {
data.shadowedLine = location.line;
data.shadowedColumn = location.column;
}
context.report({
node: variable.identifiers[0],
messageId,
data
});
}
}
}
return {
"Program:exit"(node) {
const globalScope = sourceCode.getScope(node);
const stack = globalScope.childScopes.slice();
while (stack.length) {
const scope = stack.pop();
stack.push(...scope.childScopes);
checkForShadows(scope);
}
}
};
}
};