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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");
//------------------------------------------------------------------------------
// Rule Definition
//------------------------------------------------------------------------------
module.exports = {
meta: {
type: "suggestion",
docs: {
description: "disallow variable declarations from shadowing variables declared in the outer scope",
category: "Variables",
recommended: false,
url: "https://eslint.org/docs/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"
}
}
},
additionalProperties: false
}
]
},
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) || []
};
/**
* 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.indexOf(variable.name) !== -1;
}
/**
* 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;
}
/**
* 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.hoist !== "all" && isInTdz(variable, shadowed))
) {
context.report({
node: variable.identifiers[0],
message: "'{{name}}' is already declared in the upper scope.",
data: variable
});
}
}
}
return {
"Program:exit"() {
const globalScope = context.getScope();
const stack = globalScope.childScopes.slice();
while (stack.length) {
const scope = stack.pop();
stack.push(...scope.childScopes);
checkForShadows(scope);
}
}
};
}
};
|
