management/front/dkha-web-sz-main/node_modules/eslint/lib/rules/prefer-const.js

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/**
* @fileoverview A rule to suggest using of const declaration for variables that are never reassigned after declared.
* @author Toru Nagashima
*/
"use strict";
//------------------------------------------------------------------------------
// Helpers
//------------------------------------------------------------------------------
const PATTERN_TYPE = /^(?:.+?Pattern|RestElement|SpreadProperty|ExperimentalRestProperty|Property)$/;
const DECLARATION_HOST_TYPE = /^(?:Program|BlockStatement|SwitchCase)$/;
const DESTRUCTURING_HOST_TYPE = /^(?:VariableDeclarator|AssignmentExpression)$/;
/**
* Adds multiple items to the tail of an array.
*
* @param {any[]} array - A destination to add.
* @param {any[]} values - Items to be added.
* @returns {void}
*/
const pushAll = Function.apply.bind(Array.prototype.push);
/**
* Checks whether a given node is located at `ForStatement.init` or not.
*
* @param {ASTNode} node - A node to check.
* @returns {boolean} `true` if the node is located at `ForStatement.init`.
*/
function isInitOfForStatement(node) {
return node.parent.type === "ForStatement" && node.parent.init === node;
}
/**
* Checks whether a given Identifier node becomes a VariableDeclaration or not.
*
* @param {ASTNode} identifier - An Identifier node to check.
* @returns {boolean} `true` if the node can become a VariableDeclaration.
*/
function canBecomeVariableDeclaration(identifier) {
let node = identifier.parent;
while (PATTERN_TYPE.test(node.type)) {
node = node.parent;
}
return (
node.type === "VariableDeclarator" ||
(
node.type === "AssignmentExpression" &&
node.parent.type === "ExpressionStatement" &&
DECLARATION_HOST_TYPE.test(node.parent.parent.type)
)
);
}
/**
* Gets an identifier node of a given variable.
*
* If the initialization exists or one or more reading references exist before
* the first assignment, the identifier node is the node of the declaration.
* Otherwise, the identifier node is the node of the first assignment.
*
* If the variable should not change to const, this function returns null.
* - If the variable is reassigned.
* - If the variable is never initialized nor assigned.
* - If the variable is initialized in a different scope from the declaration.
* - If the unique assignment of the variable cannot change to a declaration.
* e.g. `if (a) b = 1` / `return (b = 1)`
* - If the variable is declared in the global scope and `eslintUsed` is `true`.
* `/*exported foo` directive comment makes such variables. This rule does not
* warn such variables because this rule cannot distinguish whether the
* exported variables are reassigned or not.
*
* @param {eslint-scope.Variable} variable - A variable to get.
* @param {boolean} ignoreReadBeforeAssign -
* The value of `ignoreReadBeforeAssign` option.
* @returns {ASTNode|null}
* An Identifier node if the variable should change to const.
* Otherwise, null.
*/
function getIdentifierIfShouldBeConst(variable, ignoreReadBeforeAssign) {
if (variable.eslintUsed && variable.scope.type === "global") {
return null;
}
// Finds the unique WriteReference.
let writer = null;
let isReadBeforeInit = false;
const references = variable.references;
for (let i = 0; i < references.length; ++i) {
const reference = references[i];
if (reference.isWrite()) {
const isReassigned = (
writer !== null &&
writer.identifier !== reference.identifier
);
if (isReassigned) {
return null;
}
writer = reference;
} else if (reference.isRead() && writer === null) {
if (ignoreReadBeforeAssign) {
return null;
}
isReadBeforeInit = true;
}
}
/*
* If the assignment is from a different scope, ignore it.
* If the assignment cannot change to a declaration, ignore it.
*/
const shouldBeConst = (
writer !== null &&
writer.from === variable.scope &&
canBecomeVariableDeclaration(writer.identifier)
);
if (!shouldBeConst) {
return null;
}
if (isReadBeforeInit) {
return variable.defs[0].name;
}
return writer.identifier;
}
/**
* Gets the VariableDeclarator/AssignmentExpression node that a given reference
* belongs to.
* This is used to detect a mix of reassigned and never reassigned in a
* destructuring.
*
* @param {eslint-scope.Reference} reference - A reference to get.
* @returns {ASTNode|null} A VariableDeclarator/AssignmentExpression node or
* null.
*/
function getDestructuringHost(reference) {
if (!reference.isWrite()) {
return null;
}
let node = reference.identifier.parent;
while (PATTERN_TYPE.test(node.type)) {
node = node.parent;
}
if (!DESTRUCTURING_HOST_TYPE.test(node.type)) {
return null;
}
return node;
}
/**
* Groups by the VariableDeclarator/AssignmentExpression node that each
* reference of given variables belongs to.
* This is used to detect a mix of reassigned and never reassigned in a
* destructuring.
*
* @param {eslint-scope.Variable[]} variables - Variables to group by destructuring.
* @param {boolean} ignoreReadBeforeAssign -
* The value of `ignoreReadBeforeAssign` option.
* @returns {Map<ASTNode, ASTNode[]>} Grouped identifier nodes.
*/
function groupByDestructuring(variables, ignoreReadBeforeAssign) {
const identifierMap = new Map();
for (let i = 0; i < variables.length; ++i) {
const variable = variables[i];
const references = variable.references;
const identifier = getIdentifierIfShouldBeConst(variable, ignoreReadBeforeAssign);
let prevId = null;
for (let j = 0; j < references.length; ++j) {
const reference = references[j];
const id = reference.identifier;
/*
* Avoid counting a reference twice or more for default values of
* destructuring.
*/
if (id === prevId) {
continue;
}
prevId = id;
// Add the identifier node into the destructuring group.
const group = getDestructuringHost(reference);
if (group) {
if (identifierMap.has(group)) {
identifierMap.get(group).push(identifier);
} else {
identifierMap.set(group, [identifier]);
}
}
}
}
return identifierMap;
}
/**
* Finds the nearest parent of node with a given type.
*
* @param {ASTNode} node The node to search from.
* @param {string} type The type field of the parent node.
* @param {Function} shouldStop a predicate that returns true if the traversal should stop, and false otherwise.
* @returns {ASTNode} The closest ancestor with the specified type; null if no such ancestor exists.
*/
function findUp(node, type, shouldStop) {
if (!node || shouldStop(node)) {
return null;
}
if (node.type === type) {
return node;
}
return findUp(node.parent, type, shouldStop);
}
//------------------------------------------------------------------------------
// Rule Definition
//------------------------------------------------------------------------------
module.exports = {
meta: {
docs: {
description: "require `const` declarations for variables that are never reassigned after declared",
category: "ECMAScript 6",
recommended: false,
url: "https://eslint.org/docs/rules/prefer-const"
},
fixable: "code",
schema: [
{
type: "object",
properties: {
destructuring: { enum: ["any", "all"] },
ignoreReadBeforeAssign: { type: "boolean" }
},
additionalProperties: false
}
]
},
create(context) {
const options = context.options[0] || {};
const sourceCode = context.getSourceCode();
const checkingMixedDestructuring = options.destructuring !== "all";
const ignoreReadBeforeAssign = options.ignoreReadBeforeAssign === true;
const variables = [];
/**
* Reports given identifier nodes if all of the nodes should be declared
* as const.
*
* The argument 'nodes' is an array of Identifier nodes.
* This node is the result of 'getIdentifierIfShouldBeConst()', so it's
* nullable. In simple declaration or assignment cases, the length of
* the array is 1. In destructuring cases, the length of the array can
* be 2 or more.
*
* @param {(eslint-scope.Reference|null)[]} nodes -
* References which are grouped by destructuring to report.
* @returns {void}
*/
function checkGroup(nodes) {
const nodesToReport = nodes.filter(Boolean);
if (nodes.length && (checkingMixedDestructuring || nodesToReport.length === nodes.length)) {
const varDeclParent = findUp(nodes[0], "VariableDeclaration", parentNode => parentNode.type.endsWith("Statement"));
const shouldFix = varDeclParent &&
/*
* If there are multiple variable declarations, like {let a = 1, b = 2}, then
* do not attempt to fix if one of the declarations should be `const`. It's
* too hard to know how the developer would want to automatically resolve the issue.
*/
varDeclParent.declarations.length === 1 &&
// Don't do a fix unless the variable is initialized (or it's in a for-in or for-of loop)
(varDeclParent.parent.type === "ForInStatement" || varDeclParent.parent.type === "ForOfStatement" || varDeclParent.declarations[0].init) &&
/*
* If options.destucturing is "all", then this warning will not occur unless
* every assignment in the destructuring should be const. In that case, it's safe
* to apply the fix.
*/
nodesToReport.length === nodes.length;
nodesToReport.forEach(node => {
context.report({
node,
message: "'{{name}}' is never reassigned. Use 'const' instead.",
data: node,
fix: shouldFix ? fixer => fixer.replaceText(sourceCode.getFirstToken(varDeclParent), "const") : null
});
});
}
}
return {
"Program:exit"() {
groupByDestructuring(variables, ignoreReadBeforeAssign).forEach(checkGroup);
},
VariableDeclaration(node) {
if (node.kind === "let" && !isInitOfForStatement(node)) {
pushAll(variables, context.getDeclaredVariables(node));
}
}
};
}
};