Current File : /var/www/html/node_modules/eslint/lib/rules/no-unused-vars.js
/**
* @fileoverview Rule to flag declared but unused variables
* @author Ilya Volodin
*/
"use strict";
//------------------------------------------------------------------------------
// Requirements
//------------------------------------------------------------------------------
const astUtils = require("./utils/ast-utils");
//------------------------------------------------------------------------------
// Typedefs
//------------------------------------------------------------------------------
/**
* Bag of data used for formatting the `unusedVar` lint message.
* @typedef {Object} UnusedVarMessageData
* @property {string} varName The name of the unused var.
* @property {'defined'|'assigned a value'} action Description of the vars state.
* @property {string} additional Any additional info to be appended at the end.
*/
//------------------------------------------------------------------------------
// Rule Definition
//------------------------------------------------------------------------------
/** @type {import('../shared/types').Rule} */
module.exports = {
meta: {
type: "problem",
docs: {
description: "disallow unused variables",
recommended: true,
url: "https://eslint.org/docs/rules/no-unused-vars"
},
schema: [
{
oneOf: [
{
enum: ["all", "local"]
},
{
type: "object",
properties: {
vars: {
enum: ["all", "local"]
},
varsIgnorePattern: {
type: "string"
},
args: {
enum: ["all", "after-used", "none"]
},
ignoreRestSiblings: {
type: "boolean"
},
argsIgnorePattern: {
type: "string"
},
caughtErrors: {
enum: ["all", "none"]
},
caughtErrorsIgnorePattern: {
type: "string"
}
},
additionalProperties: false
}
]
}
],
messages: {
unusedVar: "'{{varName}}' is {{action}} but never used{{additional}}."
}
},
create(context) {
const sourceCode = context.getSourceCode();
const REST_PROPERTY_TYPE = /^(?:RestElement|(?:Experimental)?RestProperty)$/u;
const config = {
vars: "all",
args: "after-used",
ignoreRestSiblings: false,
caughtErrors: "none"
};
const firstOption = context.options[0];
if (firstOption) {
if (typeof firstOption === "string") {
config.vars = firstOption;
} else {
config.vars = firstOption.vars || config.vars;
config.args = firstOption.args || config.args;
config.ignoreRestSiblings = firstOption.ignoreRestSiblings || config.ignoreRestSiblings;
config.caughtErrors = firstOption.caughtErrors || config.caughtErrors;
if (firstOption.varsIgnorePattern) {
config.varsIgnorePattern = new RegExp(firstOption.varsIgnorePattern, "u");
}
if (firstOption.argsIgnorePattern) {
config.argsIgnorePattern = new RegExp(firstOption.argsIgnorePattern, "u");
}
if (firstOption.caughtErrorsIgnorePattern) {
config.caughtErrorsIgnorePattern = new RegExp(firstOption.caughtErrorsIgnorePattern, "u");
}
}
}
/**
* Generates the message data about the variable being defined and unused,
* including the ignore pattern if configured.
* @param {Variable} unusedVar eslint-scope variable object.
* @returns {UnusedVarMessageData} The message data to be used with this unused variable.
*/
function getDefinedMessageData(unusedVar) {
const defType = unusedVar.defs && unusedVar.defs[0] && unusedVar.defs[0].type;
let type;
let pattern;
if (defType === "CatchClause" && config.caughtErrorsIgnorePattern) {
type = "args";
pattern = config.caughtErrorsIgnorePattern.toString();
} else if (defType === "Parameter" && config.argsIgnorePattern) {
type = "args";
pattern = config.argsIgnorePattern.toString();
} else if (defType !== "Parameter" && config.varsIgnorePattern) {
type = "vars";
pattern = config.varsIgnorePattern.toString();
}
const additional = type ? `. Allowed unused ${type} must match ${pattern}` : "";
return {
varName: unusedVar.name,
action: "defined",
additional
};
}
/**
* Generate the warning message about the variable being
* assigned and unused, including the ignore pattern if configured.
* @param {Variable} unusedVar eslint-scope variable object.
* @returns {UnusedVarMessageData} The message data to be used with this unused variable.
*/
function getAssignedMessageData(unusedVar) {
const additional = config.varsIgnorePattern ? `. Allowed unused vars must match ${config.varsIgnorePattern.toString()}` : "";
return {
varName: unusedVar.name,
action: "assigned a value",
additional
};
}
//--------------------------------------------------------------------------
// Helpers
//--------------------------------------------------------------------------
const STATEMENT_TYPE = /(?:Statement|Declaration)$/u;
/**
* Determines if a given variable is being exported from a module.
* @param {Variable} variable eslint-scope variable object.
* @returns {boolean} True if the variable is exported, false if not.
* @private
*/
function isExported(variable) {
const definition = variable.defs[0];
if (definition) {
let node = definition.node;
if (node.type === "VariableDeclarator") {
node = node.parent;
} else if (definition.type === "Parameter") {
return false;
}
return node.parent.type.indexOf("Export") === 0;
}
return false;
}
/**
* Checks whether a node is a sibling of the rest property or not.
* @param {ASTNode} node a node to check
* @returns {boolean} True if the node is a sibling of the rest property, otherwise false.
*/
function hasRestSibling(node) {
return node.type === "Property" &&
node.parent.type === "ObjectPattern" &&
REST_PROPERTY_TYPE.test(node.parent.properties[node.parent.properties.length - 1].type);
}
/**
* Determines if a variable has a sibling rest property
* @param {Variable} variable eslint-scope variable object.
* @returns {boolean} True if the variable is exported, false if not.
* @private
*/
function hasRestSpreadSibling(variable) {
if (config.ignoreRestSiblings) {
const hasRestSiblingDefinition = variable.defs.some(def => hasRestSibling(def.name.parent));
const hasRestSiblingReference = variable.references.some(ref => hasRestSibling(ref.identifier.parent));
return hasRestSiblingDefinition || hasRestSiblingReference;
}
return false;
}
/**
* Determines if a reference is a read operation.
* @param {Reference} ref An eslint-scope Reference
* @returns {boolean} whether the given reference represents a read operation
* @private
*/
function isReadRef(ref) {
return ref.isRead();
}
/**
* Determine if an identifier is referencing an enclosing function name.
* @param {Reference} ref The reference to check.
* @param {ASTNode[]} nodes The candidate function nodes.
* @returns {boolean} True if it's a self-reference, false if not.
* @private
*/
function isSelfReference(ref, nodes) {
let scope = ref.from;
while (scope) {
if (nodes.indexOf(scope.block) >= 0) {
return true;
}
scope = scope.upper;
}
return false;
}
/**
* Gets a list of function definitions for a specified variable.
* @param {Variable} variable eslint-scope variable object.
* @returns {ASTNode[]} Function nodes.
* @private
*/
function getFunctionDefinitions(variable) {
const functionDefinitions = [];
variable.defs.forEach(def => {
const { type, node } = def;
// FunctionDeclarations
if (type === "FunctionName") {
functionDefinitions.push(node);
}
// FunctionExpressions
if (type === "Variable" && node.init &&
(node.init.type === "FunctionExpression" || node.init.type === "ArrowFunctionExpression")) {
functionDefinitions.push(node.init);
}
});
return functionDefinitions;
}
/**
* Checks the position of given nodes.
* @param {ASTNode} inner A node which is expected as inside.
* @param {ASTNode} outer A node which is expected as outside.
* @returns {boolean} `true` if the `inner` node exists in the `outer` node.
* @private
*/
function isInside(inner, outer) {
return (
inner.range[0] >= outer.range[0] &&
inner.range[1] <= outer.range[1]
);
}
/**
* Checks whether a given node is unused expression or not.
* @param {ASTNode} node The node itself
* @returns {boolean} The node is an unused expression.
* @private
*/
function isUnusedExpression(node) {
const parent = node.parent;
if (parent.type === "ExpressionStatement") {
return true;
}
if (parent.type === "SequenceExpression") {
const isLastExpression = parent.expressions[parent.expressions.length - 1] === node;
if (!isLastExpression) {
return true;
}
return isUnusedExpression(parent);
}
return false;
}
/**
* If a given reference is left-hand side of an assignment, this gets
* the right-hand side node of the assignment.
*
* In the following cases, this returns null.
*
* - The reference is not the LHS of an assignment expression.
* - The reference is inside of a loop.
* - The reference is inside of a function scope which is different from
* the declaration.
* @param {eslint-scope.Reference} ref A reference to check.
* @param {ASTNode} prevRhsNode The previous RHS node.
* @returns {ASTNode|null} The RHS node or null.
* @private
*/
function getRhsNode(ref, prevRhsNode) {
const id = ref.identifier;
const parent = id.parent;
const refScope = ref.from.variableScope;
const varScope = ref.resolved.scope.variableScope;
const canBeUsedLater = refScope !== varScope || astUtils.isInLoop(id);
/*
* Inherits the previous node if this reference is in the node.
* This is for `a = a + a`-like code.
*/
if (prevRhsNode && isInside(id, prevRhsNode)) {
return prevRhsNode;
}
if (parent.type === "AssignmentExpression" &&
isUnusedExpression(parent) &&
id === parent.left &&
!canBeUsedLater
) {
return parent.right;
}
return null;
}
/**
* Checks whether a given function node is stored to somewhere or not.
* If the function node is stored, the function can be used later.
* @param {ASTNode} funcNode A function node to check.
* @param {ASTNode} rhsNode The RHS node of the previous assignment.
* @returns {boolean} `true` if under the following conditions:
* - the funcNode is assigned to a variable.
* - the funcNode is bound as an argument of a function call.
* - the function is bound to a property and the object satisfies above conditions.
* @private
*/
function isStorableFunction(funcNode, rhsNode) {
let node = funcNode;
let parent = funcNode.parent;
while (parent && isInside(parent, rhsNode)) {
switch (parent.type) {
case "SequenceExpression":
if (parent.expressions[parent.expressions.length - 1] !== node) {
return false;
}
break;
case "CallExpression":
case "NewExpression":
return parent.callee !== node;
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 loops.
* @param {Reference} ref The reference to check.
* @returns {boolean} whether reference is used in the for-in loops
* @private
*/
function isForInRef(ref) {
let target = ref.identifier.parent;
// "for (var ...) { return; }"
if (target.type === "VariableDeclarator") {
target = target.parent.parent;
}
if (target.type !== "ForInStatement") {
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 (isForInRef(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;
// 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)
});
}
}
}
};
}
};
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