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/**
* @fileoverview Common utils for AST.
* @author Gyandeep Singh
*/
"use strict";
//------------------------------------------------------------------------------
// Requirements
//------------------------------------------------------------------------------
const { KEYS: eslintVisitorKeys } = require("eslint-visitor-keys");
const esutils = require("esutils");
const espree = require("espree");
const escapeRegExp = require("escape-string-regexp");
const {
breakableTypePattern,
createGlobalLinebreakMatcher,
lineBreakPattern,
shebangPattern,
} = require("../../shared/ast-utils");
const globals = require("../../../conf/globals");
const { LATEST_ECMA_VERSION } = require("../../../conf/ecma-version");
//------------------------------------------------------------------------------
// Helpers
//------------------------------------------------------------------------------
const anyFunctionPattern =
/^(?:Function(?:Declaration|Expression)|ArrowFunctionExpression)$/u;
const anyLoopPattern = /^(?:DoWhile|For|ForIn|ForOf|While)Statement$/u;
const arrayMethodWithThisArgPattern =
/^(?:every|filter|find(?:Last)?(?:Index)?|flatMap|forEach|map|some)$/u;
const arrayOrTypedArrayPattern = /Array$/u;
const bindOrCallOrApplyPattern = /^(?:bind|call|apply)$/u;
const thisTagPattern = /^[\s*]*@this/mu;
const COMMENTS_IGNORE_PATTERN =
/^\s*(?:eslint|jshint\s+|jslint\s+|istanbul\s+|globals?\s+|exported\s+|jscs)/u;
const ESLINT_DIRECTIVE_PATTERN = /^(?:eslint[- ]|(?:globals?|exported) )/u;
const LINEBREAKS = new Set(["\r\n", "\r", "\n", "\u2028", "\u2029"]);
// A set of node types that can contain a list of statements
const STATEMENT_LIST_PARENTS = new Set([
"Program",
"BlockStatement",
"StaticBlock",
"SwitchCase",
]);
const LEXICAL_DECLARATION_KINDS = new Set([
"let",
"const",
"using",
"await using",
]);
const DECIMAL_INTEGER_PATTERN = /^(?:0|0[0-7]*[89]\d*|[1-9](?:_?\d)*)$/u;
// Tests the presence of at least one LegacyOctalEscapeSequence or NonOctalDecimalEscapeSequence in a raw string
const OCTAL_OR_NON_OCTAL_DECIMAL_ESCAPE_PATTERN =
/^(?:[^\\]|\\.)*\\(?:[1-9]|0\d)/su;
const LOGICAL_ASSIGNMENT_OPERATORS = new Set(["&&=", "||=", "??="]);
/**
* All builtin global variables defined in the latest ECMAScript specification.
* @type {Record<string,boolean>} Key is the name of the variable. Value is `true` if the variable is considered writable, `false` otherwise.
*/
const ECMASCRIPT_GLOBALS = globals[`es${LATEST_ECMA_VERSION}`];
/**
* Checks reference if is non initializer and writable.
* @param {Reference} reference A reference to check.
* @param {number} index The index of the reference in the references.
* @param {Reference[]} references The array that the reference belongs to.
* @returns {boolean} Success/Failure
* @private
*/
function isModifyingReference(reference, index, references) {
const identifier = reference.identifier;
/*
* Destructuring assignments can have multiple default value, so
* possibly there are multiple writeable references for the same
* identifier.
*/
const modifyingDifferentIdentifier =
index === 0 || references[index - 1].identifier !== identifier;
return (
identifier &&
reference.init === false &&
reference.isWrite() &&
modifyingDifferentIdentifier
);
}
/**
* Checks whether the given string starts with uppercase or not.
* @param {string} s The string to check.
* @returns {boolean} `true` if the string starts with uppercase.
*/
function startsWithUpperCase(s) {
return s[0] !== s[0].toLocaleLowerCase();
}
/**
* Checks whether or not a node is a constructor.
* @param {ASTNode} node A function node to check.
* @returns {boolean} Whether or not a node is a constructor.
*/
function isES5Constructor(node) {
return node.id && startsWithUpperCase(node.id.name);
}
/**
* Finds a function node from ancestors of a node.
* @param {ASTNode} node A start node to find.
* @returns {Node|null} A found function node.
*/
function getUpperFunction(node) {
for (
let currentNode = node;
currentNode;
currentNode = currentNode.parent
) {
if (anyFunctionPattern.test(currentNode.type)) {
return currentNode;
}
}
return null;
}
/**
* Checks whether a given node is a function node or not.
* The following types are function nodes:
*
* - ArrowFunctionExpression
* - FunctionDeclaration
* - FunctionExpression
* @param {ASTNode|null} node A node to check.
* @returns {boolean} `true` if the node is a function node.
*/
function isFunction(node) {
return Boolean(node && anyFunctionPattern.test(node.type));
}
/**
* Checks whether a given node is a loop node or not.
* The following types are loop nodes:
*
* - DoWhileStatement
* - ForInStatement
* - ForOfStatement
* - ForStatement
* - WhileStatement
* @param {ASTNode|null} node A node to check.
* @returns {boolean} `true` if the node is a loop node.
*/
function isLoop(node) {
return Boolean(node && anyLoopPattern.test(node.type));
}
/**
* Checks whether the given node is in a loop or not.
* @param {ASTNode} node The node to check.
* @returns {boolean} `true` if the node is in a loop.
*/
function isInLoop(node) {
for (
let currentNode = node;
currentNode && !isFunction(currentNode);
currentNode = currentNode.parent
) {
if (isLoop(currentNode)) {
return true;
}
}
return false;
}
/**
* Determines whether the given node is a `null` literal.
* @param {ASTNode} node The node to check
* @returns {boolean} `true` if the node is a `null` literal
*/
function isNullLiteral(node) {
/*
* Checking `node.value === null` does not guarantee that a literal is a null literal.
* When parsing values that cannot be represented in the current environment (e.g. unicode
* regexes in Node 4), `node.value` is set to `null` because it wouldn't be possible to
* set `node.value` to a unicode regex. To make sure a literal is actually `null`, check
* `node.regex` instead. Also see: https://github.com/eslint/eslint/issues/8020
*/
return (
node.type === "Literal" &&
node.value === null &&
!node.regex &&
!node.bigint
);
}
/**
* Checks whether or not a node is `null` or `undefined`.
* @param {ASTNode} node A node to check.
* @returns {boolean} Whether or not the node is a `null` or `undefined`.
* @public
*/
function isNullOrUndefined(node) {
return (
isNullLiteral(node) ||
(node.type === "Identifier" && node.name === "undefined") ||
(node.type === "UnaryExpression" && node.operator === "void")
);
}
/**
* Checks whether or not a node is callee.
* @param {ASTNode} node A node to check.
* @returns {boolean} Whether or not the node is callee.
*/
function isCallee(node) {
return node.parent.type === "CallExpression" && node.parent.callee === node;
}
/**
* Returns the result of the string conversion applied to the evaluated value of the given expression node,
* if it can be determined statically.
*
* This function returns a `string` value for all `Literal` nodes and simple `TemplateLiteral` nodes only.
* In all other cases, this function returns `null`.
* @param {ASTNode} node Expression node.
* @returns {string|null} String value if it can be determined. Otherwise, `null`.
*/
function getStaticStringValue(node) {
switch (node.type) {
case "Literal":
if (node.value === null) {
if (isNullLiteral(node)) {
return String(node.value); // "null"
}
if (node.regex) {
return `/${node.regex.pattern}/${node.regex.flags}`;
}
if (node.bigint) {
return node.bigint;
}
// Otherwise, this is an unknown literal. The function will return null.
} else {
return String(node.value);
}
break;
case "TemplateLiteral":
if (node.expressions.length === 0 && node.quasis.length === 1) {
return node.quasis[0].value.cooked;
}
break;
// no default
}
return null;
}
/**
* Gets the property name of a given node.
* The node can be a MemberExpression, a Property, or a MethodDefinition.
*
* If the name is dynamic, this returns `null`.
*
* For examples:
*
* a.b // => "b"
* a["b"] // => "b"
* a['b'] // => "b"
* a[`b`] // => "b"
* a[100] // => "100"
* a[b] // => null
* a["a" + "b"] // => null
* a[tag`b`] // => null
* a[`${b}`] // => null
*
* let a = {b: 1} // => "b"
* let a = {["b"]: 1} // => "b"
* let a = {['b']: 1} // => "b"
* let a = {[`b`]: 1} // => "b"
* let a = {[100]: 1} // => "100"
* let a = {[b]: 1} // => null
* let a = {["a" + "b"]: 1} // => null
* let a = {[tag`b`]: 1} // => null
* let a = {[`${b}`]: 1} // => null
* @param {ASTNode} node The node to get.
* @returns {string|null} The property name if static. Otherwise, null.
*/
function getStaticPropertyName(node) {
let prop;
switch (node && node.type) {
case "ChainExpression":
return getStaticPropertyName(node.expression);
case "Property":
case "PropertyDefinition":
case "MethodDefinition":
case "TSPropertySignature":
case "TSMethodSignature":
prop = node.key;
break;
case "MemberExpression":
prop = node.property;
break;
// no default
}
if (prop) {
if (prop.type === "Identifier" && !node.computed) {
return prop.name;
}
return getStaticStringValue(prop);
}
return null;
}
/**
* Retrieve `ChainExpression#expression` value if the given node a `ChainExpression` node. Otherwise, pass through it.
* @param {ASTNode} node The node to address.
* @returns {ASTNode} The `ChainExpression#expression` value if the node is a `ChainExpression` node. Otherwise, the node.
*/
function skipChainExpression(node) {
return node && node.type === "ChainExpression" ? node.expression : node;
}
/**
* Check if the `actual` is an expected value.
* @param {string} actual The string value to check.
* @param {string | RegExp} expected The expected string value or pattern.
* @returns {boolean} `true` if the `actual` is an expected value.
*/
function checkText(actual, expected) {
return typeof expected === "string"
? actual === expected
: expected.test(actual);
}
/**
* Check if a given node is an Identifier node with a given name.
* @param {ASTNode} node The node to check.
* @param {string | RegExp} name The expected name or the expected pattern of the object name.
* @returns {boolean} `true` if the node is an Identifier node with the name.
*/
function isSpecificId(node, name) {
return node.type === "Identifier" && checkText(node.name, name);
}
/**
* Check if a given node is member access with a given object name and property name pair.
* This is regardless of optional or not.
* @param {ASTNode} node The node to check.
* @param {string | RegExp | null} objectName The expected name or the expected pattern of the object name. If this is nullish, this method doesn't check object.
* @param {string | RegExp | null} propertyName The expected name or the expected pattern of the property name. If this is nullish, this method doesn't check property.
* @returns {boolean} `true` if the node is member access with the object name and property name pair.
* The node is a `MemberExpression` or `ChainExpression`.
*/
function isSpecificMemberAccess(node, objectName, propertyName) {
const checkNode = skipChainExpression(node);
if (checkNode.type !== "MemberExpression") {
return false;
}
if (objectName && !isSpecificId(checkNode.object, objectName)) {
return false;
}
if (propertyName) {
const actualPropertyName = getStaticPropertyName(checkNode);
if (
typeof actualPropertyName !== "string" ||
!checkText(actualPropertyName, propertyName)
) {
return false;
}
}
return true;
}
/**
* Check if two literal nodes are the same value.
* @param {ASTNode} left The Literal node to compare.
* @param {ASTNode} right The other Literal node to compare.
* @returns {boolean} `true` if the two literal nodes are the same value.
*/
function equalLiteralValue(left, right) {
// RegExp literal.
if (left.regex || right.regex) {
return Boolean(
left.regex &&
right.regex &&
left.regex.pattern === right.regex.pattern &&
left.regex.flags === right.regex.flags,
);
}
// BigInt literal.
if (left.bigint || right.bigint) {
return left.bigint === right.bigint;
}
return left.value === right.value;
}
/**
* Check if two expressions reference the same value. For example:
* a = a
* a.b = a.b
* a[0] = a[0]
* a['b'] = a['b']
* @param {ASTNode} left The left side of the comparison.
* @param {ASTNode} right The right side of the comparison.
* @param {boolean} [disableStaticComputedKey] Don't address `a.b` and `a["b"]` are the same if `true`. For backward compatibility.
* @returns {boolean} `true` if both sides match and reference the same value.
*/
function isSameReference(left, right, disableStaticComputedKey = false) {
if (left.type !== right.type) {
// Handle `a.b` and `a?.b` are samely.
if (left.type === "ChainExpression") {
return isSameReference(
left.expression,
right,
disableStaticComputedKey,
);
}
if (right.type === "ChainExpression") {
return isSameReference(
left,
right.expression,
disableStaticComputedKey,
);
}
return false;
}
switch (left.type) {
case "Super":
case "ThisExpression":
return true;
case "Identifier":
case "PrivateIdentifier":
return left.name === right.name;
case "Literal":
return equalLiteralValue(left, right);
case "ChainExpression":
return isSameReference(
left.expression,
right.expression,
disableStaticComputedKey,
);
case "MemberExpression": {
if (!disableStaticComputedKey) {
const nameA = getStaticPropertyName(left);
// x.y = x["y"]
if (nameA !== null) {
return (
isSameReference(
left.object,
right.object,
disableStaticComputedKey,
) && nameA === getStaticPropertyName(right)
);
}
}
/*
* x[0] = x[0]
* x[y] = x[y]
* x.y = x.y
*/
return (
left.computed === right.computed &&
isSameReference(
left.object,
right.object,
disableStaticComputedKey,
) &&
isSameReference(
left.property,
right.property,
disableStaticComputedKey,
)
);
}
default:
return false;
}
}
/**
* Checks whether or not a node is `Reflect.apply`.
* @param {ASTNode} node A node to check.
* @returns {boolean} Whether or not the node is a `Reflect.apply`.
*/
function isReflectApply(node) {
return isSpecificMemberAccess(node, "Reflect", "apply");
}
/**
* Checks whether or not a node is `Array.from`.
* @param {ASTNode} node A node to check.
* @returns {boolean} Whether or not the node is a `Array.from`.
*/
function isArrayFromMethod(node) {
return isSpecificMemberAccess(node, arrayOrTypedArrayPattern, "from");
}
/**
* Checks whether or not a node is a method which expects a function as a first argument, and `thisArg` as a second argument.
* @param {ASTNode} node A node to check.
* @returns {boolean} Whether or not the node is a method which expects a function as a first argument, and `thisArg` as a second argument.
*/
function isMethodWhichHasThisArg(node) {
return isSpecificMemberAccess(node, null, arrayMethodWithThisArgPattern);
}
/**
* Creates the negate function of the given function.
* @param {Function} f The function to negate.
* @returns {Function} Negated function.
*/
function negate(f) {
return token => !f(token);
}
/**
* Checks whether or not a node has a `@this` tag in its comments.
* @param {ASTNode} node A node to check.
* @param {SourceCode} sourceCode A SourceCode instance to get comments.
* @returns {boolean} Whether or not the node has a `@this` tag in its comments.
*/
function hasJSDocThisTag(node, sourceCode) {
const jsdocComment = sourceCode.getJSDocComment(node);
if (jsdocComment && thisTagPattern.test(jsdocComment.value)) {
return true;
}
// Checks `@this` in its leading comments for callbacks,
// because callbacks don't have its JSDoc comment.
// e.g.
// sinon.test(/* @this sinon.Sandbox */function() { this.spy(); });
return sourceCode
.getCommentsBefore(node)
.some(comment => thisTagPattern.test(comment.value));
}
/**
* Determines if a node is surrounded by parentheses.
* @param {SourceCode} sourceCode The ESLint source code object
* @param {ASTNode} node The node to be checked.
* @returns {boolean} True if the node is parenthesised.
* @private
*/
function isParenthesised(sourceCode, node) {
const previousToken = sourceCode.getTokenBefore(node),
nextToken = sourceCode.getTokenAfter(node);
return (
Boolean(previousToken && nextToken) &&
previousToken.value === "(" &&
previousToken.range[1] <= node.range[0] &&
nextToken.value === ")" &&
nextToken.range[0] >= node.range[1]
);
}
/**
* Checks if the given token is a `=` token or not.
* @param {Token} token The token to check.
* @returns {boolean} `true` if the token is a `=` token.
*/
function isEqToken(token) {
return token.value === "=" && token.type === "Punctuator";
}
/**
* Checks if the given token is an arrow token or not.
* @param {Token} token The token to check.
* @returns {boolean} `true` if the token is an arrow token.
*/
function isArrowToken(token) {
return token.value === "=>" && token.type === "Punctuator";
}
/**
* Checks if the given token is a comma token or not.
* @param {Token} token The token to check.
* @returns {boolean} `true` if the token is a comma token.
*/
function isCommaToken(token) {
return token.value === "," && token.type === "Punctuator";
}
/**
* Checks if the given token is a dot token or not.
* @param {Token} token The token to check.
* @returns {boolean} `true` if the token is a dot token.
*/
function isDotToken(token) {
return token.value === "." && token.type === "Punctuator";
}
/**
* Checks if the given token is a `?.` token or not.
* @param {Token} token The token to check.
* @returns {boolean} `true` if the token is a `?.` token.
*/
function isQuestionDotToken(token) {
return token.value === "?." && token.type === "Punctuator";
}
/**
* Checks if the given token is a semicolon token or not.
* @param {Token} token The token to check.
* @returns {boolean} `true` if the token is a semicolon token.
*/
function isSemicolonToken(token) {
return token.value === ";" && token.type === "Punctuator";
}
/**
* Checks if the given token is a colon token or not.
* @param {Token} token The token to check.
* @returns {boolean} `true` if the token is a colon token.
*/
function isColonToken(token) {
return token.value === ":" && token.type === "Punctuator";
}
/**
* Checks if the given token is an opening parenthesis token or not.
* @param {Token} token The token to check.
* @returns {boolean} `true` if the token is an opening parenthesis token.
*/
function isOpeningParenToken(token) {
return token.value === "(" && token.type === "Punctuator";
}
/**
* Checks if the given token is a closing parenthesis token or not.
* @param {Token} token The token to check.
* @returns {boolean} `true` if the token is a closing parenthesis token.
*/
function isClosingParenToken(token) {
return token.value === ")" && token.type === "Punctuator";
}
/**
* Checks if the given token is an opening square bracket token or not.
* @param {Token} token The token to check.
* @returns {boolean} `true` if the token is an opening square bracket token.
*/
function isOpeningBracketToken(token) {
return token.value === "[" && token.type === "Punctuator";
}
/**
* Checks if the given token is a closing square bracket token or not.
* @param {Token} token The token to check.
* @returns {boolean} `true` if the token is a closing square bracket token.
*/
function isClosingBracketToken(token) {
return token.value === "]" && token.type === "Punctuator";
}
/**
* Checks if the given token is an opening brace token or not.
* @param {Token} token The token to check.
* @returns {boolean} `true` if the token is an opening brace token.
*/
function isOpeningBraceToken(token) {
return token.value === "{" && token.type === "Punctuator";
}
/**
* Checks if the given token is a closing brace token or not.
* @param {Token} token The token to check.
* @returns {boolean} `true` if the token is a closing brace token.
*/
function isClosingBraceToken(token) {
return token.value === "}" && token.type === "Punctuator";
}
/**
* Checks if the given token is a comment token or not.
* @param {Token} token The token to check.
* @returns {boolean} `true` if the token is a comment token.
*/
function isCommentToken(token) {
return (
token.type === "Line" ||
token.type === "Block" ||
token.type === "Shebang"
);
}
/**
* Checks if the given token is a keyword token or not.
* @param {Token} token The token to check.
* @returns {boolean} `true` if the token is a keyword token.
*/
function isKeywordToken(token) {
return token.type === "Keyword";
}
/**
* Gets the `(` token of the given function node.
* @param {ASTNode} node The function node to get.
* @param {SourceCode} sourceCode The source code object to get tokens.
* @returns {Token} `(` token.
*/
function getOpeningParenOfParams(node, sourceCode) {
// If the node is an arrow function and doesn't have parens, this returns the identifier of the first param.
if (node.type === "ArrowFunctionExpression" && node.params.length === 1) {
const argToken = sourceCode.getFirstToken(node.params[0]);
const maybeParenToken = sourceCode.getTokenBefore(argToken);
return isOpeningParenToken(maybeParenToken)
? maybeParenToken
: argToken;
}
// Otherwise, returns paren.
return node.id
? sourceCode.getTokenAfter(node.id, isOpeningParenToken)
: sourceCode.getFirstToken(node, isOpeningParenToken);
}
/**
* Checks whether or not the tokens of two given nodes are same.
* @param {ASTNode} left A node 1 to compare.
* @param {ASTNode} right A node 2 to compare.
* @param {SourceCode} sourceCode The ESLint source code object.
* @returns {boolean} the source code for the given node.
*/
function equalTokens(left, right, sourceCode) {
const tokensL = sourceCode.getTokens(left);
const tokensR = sourceCode.getTokens(right);
if (tokensL.length !== tokensR.length) {
return false;
}
for (let i = 0; i < tokensL.length; ++i) {
if (
tokensL[i].type !== tokensR[i].type ||
tokensL[i].value !== tokensR[i].value
) {
return false;
}
}
return true;
}
/**
* Check if the given node is a true logical expression or not.
*
* The three binary expressions logical-or (`||`), logical-and (`&&`), and
* coalesce (`??`) are known as `ShortCircuitExpression`.
* But ESTree represents those by `LogicalExpression` node.
*
* This function rejects coalesce expressions of `LogicalExpression` node.
* @param {ASTNode} node The node to check.
* @returns {boolean} `true` if the node is `&&` or `||`.
* @see https://tc39.es/ecma262/#prod-ShortCircuitExpression
*/
function isLogicalExpression(node) {
return (
node.type === "LogicalExpression" &&
(node.operator === "&&" || node.operator === "||")
);
}
/**
* Check if the given node is a nullish coalescing expression or not.
*
* The three binary expressions logical-or (`||`), logical-and (`&&`), and
* coalesce (`??`) are known as `ShortCircuitExpression`.
* But ESTree represents those by `LogicalExpression` node.
*
* This function finds only coalesce expressions of `LogicalExpression` node.
* @param {ASTNode} node The node to check.
* @returns {boolean} `true` if the node is `??`.
*/
function isCoalesceExpression(node) {
return node.type === "LogicalExpression" && node.operator === "??";
}
/**
* Check if given two nodes are the pair of a logical expression and a coalesce expression.
* @param {ASTNode} left A node to check.
* @param {ASTNode} right Another node to check.
* @returns {boolean} `true` if the two nodes are the pair of a logical expression and a coalesce expression.
*/
function isMixedLogicalAndCoalesceExpressions(left, right) {
return (
(isLogicalExpression(left) && isCoalesceExpression(right)) ||
(isCoalesceExpression(left) && isLogicalExpression(right))
);
}
/**
* Checks if the given operator is a logical assignment operator.
* @param {string} operator The operator to check.
* @returns {boolean} `true` if the operator is a logical assignment operator.
*/
function isLogicalAssignmentOperator(operator) {
return LOGICAL_ASSIGNMENT_OPERATORS.has(operator);
}
/**
* Get the colon token of the given SwitchCase node.
* @param {ASTNode} node The SwitchCase node to get.
* @param {SourceCode} sourceCode The source code object to get tokens.
* @returns {Token} The colon token of the node.
*/
function getSwitchCaseColonToken(node, sourceCode) {
if (node.test) {
return sourceCode.getTokenAfter(node.test, isColonToken);
}
return sourceCode.getFirstToken(node, 1);
}
/**
* Gets ESM module export name represented by the given node.
* @param {ASTNode} node `Identifier` or string `Literal` node in a position
* that represents a module export name:
* - `ImportSpecifier#imported`
* - `ExportSpecifier#local` (if it is a re-export from another module)
* - `ExportSpecifier#exported`
* - `ExportAllDeclaration#exported`
* @returns {string} The module export name.
*/
function getModuleExportName(node) {
if (node.type === "Identifier") {
return node.name;
}
// string literal
return node.value;
}
/**
* Returns literal's value converted to the Boolean type
* @param {ASTNode} node any `Literal` node
* @returns {boolean | null} `true` when node is truthy, `false` when node is falsy,
* `null` when it cannot be determined.
*/
function getBooleanValue(node) {
if (node.value === null) {
/*
* it might be a null literal or bigint/regex literal in unsupported environments .
* https://github.com/estree/estree/blob/14df8a024956ea289bd55b9c2226a1d5b8a473ee/es5.md#regexpliteral
* https://github.com/estree/estree/blob/14df8a024956ea289bd55b9c2226a1d5b8a473ee/es2020.md#bigintliteral
*/
if (node.raw === "null") {
return false;
}
// regex is always truthy
if (typeof node.regex === "object") {
return true;
}
return null;
}
return !!node.value;
}
/**
* Checks if a branch node of LogicalExpression short circuits the whole condition
* @param {ASTNode} node The branch of main condition which needs to be checked
* @param {string} operator The operator of the main LogicalExpression.
* @returns {boolean} true when condition short circuits whole condition
*/
function isLogicalIdentity(node, operator) {
switch (node.type) {
case "Literal":
return (
(operator === "||" && getBooleanValue(node) === true) ||
(operator === "&&" && getBooleanValue(node) === false)
);
case "UnaryExpression":
return operator === "&&" && node.operator === "void";
case "LogicalExpression":
/*
* handles `a && false || b`
* `false` is an identity element of `&&` but not `||`
*/
return (
operator === node.operator &&
(isLogicalIdentity(node.left, operator) ||
isLogicalIdentity(node.right, operator))
);
case "AssignmentExpression":
return (
["||=", "&&="].includes(node.operator) &&
operator === node.operator.slice(0, -1) &&
isLogicalIdentity(node.right, operator)
);
// no default
}
return false;
}
/**
* Checks if an identifier is a reference to a global variable.
* @param {Scope} scope The scope in which the identifier is referenced.
* @param {ASTNode} node An identifier node to check.
* @returns {boolean} `true` if the identifier is a reference to a global variable.
*/
function isReferenceToGlobalVariable(scope, node) {
const reference = scope.references.find(ref => ref.identifier === node);
return Boolean(
reference &&
reference.resolved &&
reference.resolved.scope.type === "global" &&
reference.resolved.defs.length === 0,
);
}
/**
* Checks if a node has a constant truthiness value.
* @param {Scope} scope Scope in which the node appears.
* @param {ASTNode} node The AST node to check.
* @param {boolean} inBooleanPosition `true` if checking the test of a
* condition. `false` in all other cases. When `false`, checks if -- for
* both string and number -- if coerced to that type, the value will
* be constant.
* @returns {boolean} true when node's truthiness is constant
* @private
*/
function isConstant(scope, node, inBooleanPosition) {
// node.elements can return null values in the case of sparse arrays ex. [,]
if (!node) {
return true;
}
switch (node.type) {
case "Literal":
case "ArrowFunctionExpression":
case "FunctionExpression":
return true;
case "ClassExpression":
case "ObjectExpression":
/**
* In theory objects like:
*
* `{toString: () => a}`
* `{valueOf: () => a}`
*
* Or a classes like:
*
* `class { static toString() { return a } }`
* `class { static valueOf() { return a } }`
*
* Are not constant verifiably when `inBooleanPosition` is
* false, but it's an edge case we've opted not to handle.
*/
return true;
case "TemplateLiteral":
return (
(inBooleanPosition &&
node.quasis.some(quasi => quasi.value.cooked.length)) ||
node.expressions.every(exp => isConstant(scope, exp, false))
);
case "ArrayExpression": {
if (!inBooleanPosition) {
return node.elements.every(element =>
isConstant(scope, element, false),
);
}
return true;
}
case "UnaryExpression":
if (
node.operator === "void" ||
(node.operator === "typeof" && inBooleanPosition)
) {
return true;
}
if (node.operator === "!") {
return isConstant(scope, node.argument, true);
}
return isConstant(scope, node.argument, false);
case "BinaryExpression":
return (
isConstant(scope, node.left, false) &&
isConstant(scope, node.right, false) &&
node.operator !== "in"
);
case "LogicalExpression": {
const isLeftConstant = isConstant(
scope,
node.left,
inBooleanPosition,
);
const isRightConstant = isConstant(
scope,
node.right,
inBooleanPosition,
);
const isLeftShortCircuit =
isLeftConstant && isLogicalIdentity(node.left, node.operator);
const isRightShortCircuit =
inBooleanPosition &&
isRightConstant &&
isLogicalIdentity(node.right, node.operator);
return (
(isLeftConstant && isRightConstant) ||
isLeftShortCircuit ||
isRightShortCircuit
);
}
case "NewExpression":
return inBooleanPosition;
case "AssignmentExpression":
if (node.operator === "=") {
return isConstant(scope, node.right, inBooleanPosition);
}
if (["||=", "&&="].includes(node.operator) && inBooleanPosition) {
return isLogicalIdentity(
node.right,
node.operator.slice(0, -1),
);
}
return false;
case "SequenceExpression":
return isConstant(
scope,
node.expressions.at(-1),
inBooleanPosition,
);
case "SpreadElement":
return isConstant(scope, node.argument, inBooleanPosition);
case "CallExpression":
if (
node.callee.type === "Identifier" &&
node.callee.name === "Boolean"
) {
if (
node.arguments.length === 0 ||
isConstant(scope, node.arguments[0], true)
) {
return isReferenceToGlobalVariable(scope, node.callee);
}
}
return false;
case "Identifier":
return (
node.name === "undefined" &&
isReferenceToGlobalVariable(scope, node)
);
// no default
}
return false;
}
/**
* Checks whether a node is an ExpressionStatement at the top level of a file, function body, or TypeScript module block.
* A top-level ExpressionStatement node is a directive if it contains a single unparenthesized
* string literal and if it occurs either as the first sibling or immediately after another
* directive.
* @param {ASTNode} node The node to check.
* @returns {boolean} Whether or not the node is an ExpressionStatement at the top level of a
* file, function body, or TypeScript module block.
*/
function isTopLevelExpressionStatement(node) {
if (node.type !== "ExpressionStatement") {
return false;
}
const parent = node.parent;
return (
parent.type === "Program" ||
parent.type === "TSModuleBlock" ||
(parent.type === "BlockStatement" && isFunction(parent.parent))
);
}
/**
* Check whether the given node is a part of a directive prologue or not.
* @param {ASTNode} node The node to check.
* @returns {boolean} `true` if the node is a part of directive prologue.
*/
function isDirective(node) {
return (
node.type === "ExpressionStatement" &&
typeof node.directive === "string"
);
}
/**
* Tests if a node appears at the beginning of an ancestor ExpressionStatement node.
* @param {ASTNode} node The node to check.
* @returns {boolean} Whether the node appears at the beginning of an ancestor ExpressionStatement node.
*/
function isStartOfExpressionStatement(node) {
const start = node.range[0];
let ancestor = node;
while ((ancestor = ancestor.parent) && ancestor.range[0] === start) {
if (ancestor.type === "ExpressionStatement") {
return true;
}
}
return false;
}
/**
* Determines whether an opening parenthesis `(`, bracket `[` or backtick ``` ` ``` needs to be preceded by a semicolon.
* This opening parenthesis or bracket should be at the start of an `ExpressionStatement`, a `MethodDefinition` or at
* the start of the body of an `ArrowFunctionExpression`.
* @type {(sourceCode: SourceCode, node: ASTNode) => boolean}
* @param {SourceCode} sourceCode The source code object.
* @param {ASTNode} node A node at the position where an opening parenthesis or bracket will be inserted.
* @returns {boolean} Whether a semicolon is required before the opening parenthesis or bracket.
*/
let needsPrecedingSemicolon;
{
const BREAK_OR_CONTINUE = new Set(["BreakStatement", "ContinueStatement"]);
// Declaration types that cannot be continued by a punctuator when ending with a string Literal that is a direct child.
const DECLARATIONS = new Set([
"ExportAllDeclaration",
"ExportNamedDeclaration",
"ImportDeclaration",
]);
const IDENTIFIER_OR_KEYWORD = new Set(["Identifier", "Keyword"]);
// Keywords that can immediately precede an ExpressionStatement node, mapped to the their node types.
const NODE_TYPES_BY_KEYWORD = {
__proto__: null,
break: "BreakStatement",
continue: "ContinueStatement",
debugger: "DebuggerStatement",
do: "DoWhileStatement",
else: "IfStatement",
return: "ReturnStatement",
yield: "YieldExpression",
};
/*
* Before an opening parenthesis, postfix `++` and `--` always trigger ASI;
* the tokens `:`, `;`, `{` and `=>` don't expect a semicolon, as that would count as an empty statement.
*/
const PUNCTUATORS = new Set([":", ";", "{", "=>", "++", "--"]);
/*
* Statements that can contain an `ExpressionStatement` after a closing parenthesis.
* DoWhileStatement is an exception in that it always triggers ASI after the closing parenthesis.
*/
const STATEMENTS = new Set([
"DoWhileStatement",
"ForInStatement",
"ForOfStatement",
"ForStatement",
"IfStatement",
"WhileStatement",
"WithStatement",
]);
const TS_TYPE_NODE_TYPES = new Set([
"TSAsExpression",
"TSSatisfiesExpression",
"TSTypeAliasDeclaration",
"TSTypeAnnotation",
]);
/**
* Determines whether a specified node is inside a TypeScript type context.
* @param {ASTNode} node The node to check.
* @returns {boolean} Whether the node is inside a TypeScript type context.
*/
function isInType(node) {
for (let currNode = node; ; ) {
const { parent } = currNode;
if (!parent) {
break;
}
if (
TS_TYPE_NODE_TYPES.has(parent.type) &&
currNode === parent.typeAnnotation
) {
return true;
}
currNode = parent;
}
return false;
}
needsPrecedingSemicolon = function (sourceCode, node) {
const prevToken = sourceCode.getTokenBefore(node);
if (
!prevToken ||
(prevToken.type === "Punctuator" &&
PUNCTUATORS.has(prevToken.value))
) {
return false;
}
const prevNode = sourceCode.getNodeByRangeIndex(prevToken.range[0]);
if (
prevNode.type === "TSDeclareFunction" ||
prevNode.parent.type === "TSImportEqualsDeclaration" ||
prevNode.parent.parent?.type === "TSImportEqualsDeclaration" ||
TS_TYPE_NODE_TYPES.has(prevNode.type) ||
isInType(prevNode)
) {
return false;
}
if (isClosingParenToken(prevToken)) {
return !STATEMENTS.has(prevNode.type);
}
if (isClosingBraceToken(prevToken)) {
return (
(prevNode.type === "BlockStatement" &&
prevNode.parent.type === "FunctionExpression" &&
prevNode.parent.parent.type !== "MethodDefinition") ||
(prevNode.type === "ClassBody" &&
prevNode.parent.type === "ClassExpression") ||
prevNode.type === "ObjectExpression"
);
}
if (IDENTIFIER_OR_KEYWORD.has(prevToken.type)) {
if (
prevNode.parent.type === "VariableDeclarator" &&
!prevNode.parent.init
) {
return false;
}
if (BREAK_OR_CONTINUE.has(prevNode.parent.type)) {
return false;
}
const keyword = prevToken.value;
const nodeType = NODE_TYPES_BY_KEYWORD[keyword];
return prevNode.type !== nodeType;
}
if (prevToken.type === "String") {
return !DECLARATIONS.has(prevNode.parent.type);
}
return true;
};
}
/**
* Checks if a node is used as an import attribute key, either in a static or dynamic import.
* @param {ASTNode} node The node to check.
* @returns {boolean} Whether the node is used as an import attribute key.
*/
function isImportAttributeKey(node) {
const { parent } = node;
// static import/re-export
if (parent.type === "ImportAttribute" && parent.key === node) {
return true;
}
// dynamic import
if (
parent.type === "Property" &&
!parent.computed &&
(parent.key === node ||
(parent.value === node && parent.shorthand && !parent.method)) &&
parent.parent.type === "ObjectExpression"
) {
const objectExpression = parent.parent;
const objectExpressionParent = objectExpression.parent;
if (
objectExpressionParent.type === "ImportExpression" &&
objectExpressionParent.options === objectExpression
) {
return true;
}
// nested key
if (
objectExpressionParent.type === "Property" &&
objectExpressionParent.value === objectExpression
) {
return isImportAttributeKey(objectExpressionParent.key);
}
}
return false;
}
//------------------------------------------------------------------------------
// Public Interface
//------------------------------------------------------------------------------
module.exports = {
COMMENTS_IGNORE_PATTERN,
LINEBREAKS,
LINEBREAK_MATCHER: lineBreakPattern,
SHEBANG_MATCHER: shebangPattern,
STATEMENT_LIST_PARENTS,
ECMASCRIPT_GLOBALS,
/**
* Determines whether two adjacent tokens are on the same line.
* @param {Object} left The left token object.
* @param {Object} right The right token object.
* @returns {boolean} Whether or not the tokens are on the same line.
* @public
*/
isTokenOnSameLine(left, right) {
return left.loc.end.line === right.loc.start.line;
},
isNullOrUndefined,
isCallee,
isES5Constructor,
getUpperFunction,
isFunction,
isLoop,
isInLoop,
isArrayFromMethod,
isParenthesised,
createGlobalLinebreakMatcher,
equalTokens,
isArrowToken,
isClosingBraceToken,
isClosingBracketToken,
isClosingParenToken,
isColonToken,
isCommaToken,
isCommentToken,
isDotToken,
isQuestionDotToken,
isKeywordToken,
isNotClosingBraceToken: negate(isClosingBraceToken),
isNotClosingBracketToken: negate(isClosingBracketToken),
isNotClosingParenToken: negate(isClosingParenToken),
isNotColonToken: negate(isColonToken),
isNotCommaToken: negate(isCommaToken),
isNotDotToken: negate(isDotToken),
isNotQuestionDotToken: negate(isQuestionDotToken),
isNotOpeningBraceToken: negate(isOpeningBraceToken),
isNotOpeningBracketToken: negate(isOpeningBracketToken),
isNotOpeningParenToken: negate(isOpeningParenToken),
isNotSemicolonToken: negate(isSemicolonToken),
isOpeningBraceToken,
isOpeningBracketToken,
isOpeningParenToken,
isSemicolonToken,
isEqToken,
/**
* Checks whether or not a given node is a string literal.
* @param {ASTNode} node A node to check.
* @returns {boolean} `true` if the node is a string literal.
*/
isStringLiteral(node) {
return (
(node.type === "Literal" && typeof node.value === "string") ||
node.type === "TemplateLiteral"
);
},
/**
* Checks whether a given node is a breakable statement or not.
* The node is breakable if the node is one of the following type:
*
* - DoWhileStatement
* - ForInStatement
* - ForOfStatement
* - ForStatement
* - SwitchStatement
* - WhileStatement
* @param {ASTNode} node A node to check.
* @returns {boolean} `true` if the node is breakable.
*/
isBreakableStatement(node) {
return breakableTypePattern.test(node.type);
},
/**
* Gets references which are non initializer and writable.
* @param {Reference[]} references An array of references.
* @returns {Reference[]} An array of only references which are non initializer and writable.
* @public
*/
getModifyingReferences(references) {
return references.filter(isModifyingReference);
},
/**
* Validate that a string passed in is surrounded by the specified character
* @param {string} val The text to check.
* @param {string} character The character to see if it's surrounded by.
* @returns {boolean} True if the text is surrounded by the character, false if not.
* @private
*/
isSurroundedBy(val, character) {
return val[0] === character && val.at(-1) === character;
},
/**
* Returns whether the provided node is an ESLint directive comment or not
* @param {Line|Block} node The comment token to be checked
* @returns {boolean} `true` if the node is an ESLint directive comment
*/
isDirectiveComment(node) {
const comment = node.value.trim();
return (
(node.type === "Line" && comment.startsWith("eslint-")) ||
(node.type === "Block" && ESLINT_DIRECTIVE_PATTERN.test(comment))
);
},
/**
* Gets the trailing statement of a given node.
*
* if (code)
* consequent;
*
* When taking this `IfStatement`, returns `consequent;` statement.
* @param {ASTNode} A node to get.
* @returns {ASTNode|null} The trailing statement's node.
*/
getTrailingStatement: esutils.ast.trailingStatement,
/**
* Finds the variable by a given name in a given scope and its upper scopes.
* @param {eslint-scope.Scope} initScope A scope to start find.
* @param {string} name A variable name to find.
* @returns {eslint-scope.Variable|null} A found variable or `null`.
*/
getVariableByName(initScope, name) {
let scope = initScope;
while (scope) {
const variable = scope.set.get(name);
if (variable) {
return variable;
}
scope = scope.upper;
}
return null;
},
/**
* Checks whether or not a given function node is the default `this` binding.
*
* First, this checks the node:
*
* - The given node is not in `PropertyDefinition#value` position.
* - The given node is not `StaticBlock`.
* - The function name does not start with uppercase. It's a convention to capitalize the names
* of constructor functions. This check is not performed if `capIsConstructor` is set to `false`.
* - The function does not have a JSDoc comment that has a @this tag.
*
* Next, this checks the location of the node.
* If the location is below, this judges `this` is valid.
*
* - The location is not on an object literal.
* - The location is not assigned to a variable which starts with an uppercase letter. Applies to anonymous
* functions only, as the name of the variable is considered to be the name of the function in this case.
* This check is not performed if `capIsConstructor` is set to `false`.
* - The location is not on an ES2015 class.
* - Its `bind`/`call`/`apply` method is not called directly.
* - The function is not a callback of array methods (such as `.forEach()`) if `thisArg` is given.
* @param {ASTNode} node A function node to check. It also can be an implicit function, like `StaticBlock`
* or any expression that is `PropertyDefinition#value` node.
* @param {SourceCode} sourceCode A SourceCode instance to get comments.
* @param {boolean} [capIsConstructor = true] `false` disables the assumption that functions which name starts
* with an uppercase or are assigned to a variable which name starts with an uppercase are constructors.
* @returns {boolean} The function node is the default `this` binding.
*/
isDefaultThisBinding(node, sourceCode, { capIsConstructor = true } = {}) {
/*
* Class field initializers are implicit functions, but ESTree doesn't have the AST node of field initializers.
* Therefore, A expression node at `PropertyDefinition#value` is a function.
* In this case, `this` is always not default binding.
*/
if (
node.parent.type === "PropertyDefinition" &&
node.parent.value === node
) {
return false;
}
// Class static blocks are implicit functions. In this case, `this` is always not default binding.
if (node.type === "StaticBlock") {
return false;
}
// Check if the function has a parameter named `this`.
if (
(node.type === "FunctionDeclaration" ||
node.type === "FunctionExpression") &&
node.params.some(
param => param.type === "Identifier" && param.name === "this",
)
) {
return false;
}
if (
(capIsConstructor && isES5Constructor(node)) ||
hasJSDocThisTag(node, sourceCode)
) {
return false;
}
const isAnonymous = node.id === null;
let currentNode = node;
while (currentNode) {
const parent = currentNode.parent;
switch (parent.type) {
/*
* Looks up the destination.
* e.g., obj.foo = nativeFoo || function foo() { ... };
*/
case "LogicalExpression":
case "ConditionalExpression":
case "ChainExpression":
currentNode = parent;
break;
/*
* If the upper function is IIFE, checks the destination of the return value.
* e.g.
* obj.foo = (function() {
* // setup...
* return function foo() { ... };
* })();
* obj.foo = (() =>
* function foo() { ... }
* )();
*/
case "ReturnStatement": {
const func = getUpperFunction(parent);
if (func === null || !isCallee(func)) {
return true;
}
currentNode = func.parent;
break;
}
case "ArrowFunctionExpression":
if (currentNode !== parent.body || !isCallee(parent)) {
return true;
}
currentNode = parent.parent;
break;
/*
* e.g.
* var obj = { foo() { ... } };
* var obj = { foo: function() { ... } };
* class A { constructor() { ... } }
* class A { foo() { ... } }
* class A { get foo() { ... } }
* class A { set foo() { ... } }
* class A { static foo() { ... } }
* class A { foo = function() { ... } }
*/
case "Property":
case "PropertyDefinition":
case "MethodDefinition":
return parent.value !== currentNode;
/*
* e.g.
* obj.foo = function foo() { ... };
* Foo = function() { ... };
* [obj.foo = function foo() { ... }] = a;
* [Foo = function() { ... }] = a;
*/
case "AssignmentExpression":
case "AssignmentPattern":
if (parent.left.type === "MemberExpression") {
return false;
}
if (
capIsConstructor &&
isAnonymous &&
parent.left.type === "Identifier" &&
startsWithUpperCase(parent.left.name)
) {
return false;
}
return true;
/*
* e.g.
* var Foo = function() { ... };
*/
case "VariableDeclarator":
return !(
capIsConstructor &&
isAnonymous &&
parent.init === currentNode &&
parent.id.type === "Identifier" &&
startsWithUpperCase(parent.id.name)
);
/*
* e.g.
* var foo = function foo() { ... }.bind(obj);
* (function foo() { ... }).call(obj);
* (function foo() { ... }).apply(obj, []);
*/
case "MemberExpression":
if (
parent.object === currentNode &&
isSpecificMemberAccess(
parent,
null,
bindOrCallOrApplyPattern,
)
) {
const maybeCalleeNode =
parent.parent.type === "ChainExpression"
? parent.parent
: parent;
return !(
isCallee(maybeCalleeNode) &&
maybeCalleeNode.parent.arguments.length >= 1 &&
!isNullOrUndefined(
maybeCalleeNode.parent.arguments[0],
)
);
}
return true;
/*
* e.g.
* Reflect.apply(function() {}, obj, []);
* Array.from([], function() {}, obj);
* list.forEach(function() {}, obj);
*/
case "CallExpression":
if (isReflectApply(parent.callee)) {
return (
parent.arguments.length !== 3 ||
parent.arguments[0] !== currentNode ||
isNullOrUndefined(parent.arguments[1])
);
}
if (isArrayFromMethod(parent.callee)) {
return (
parent.arguments.length !== 3 ||
parent.arguments[1] !== currentNode ||
isNullOrUndefined(parent.arguments[2])
);
}
if (isMethodWhichHasThisArg(parent.callee)) {
return (
parent.arguments.length !== 2 ||
parent.arguments[0] !== currentNode ||
isNullOrUndefined(parent.arguments[1])
);
}
return true;
// Otherwise `this` is default.
default:
return true;
}
}
/* c8 ignore next */
return true;
},
/**
* Get the precedence level based on the node type
* @param {ASTNode} node node to evaluate
* @returns {number} precedence level
* @private
*/
getPrecedence(node) {
switch (node.type) {
case "SequenceExpression":
return 0;
case "AssignmentExpression":
case "ArrowFunctionExpression":
case "YieldExpression":
return 1;
case "ConditionalExpression":
return 3;
case "LogicalExpression":
switch (node.operator) {
case "||":
case "??":
return 4;
case "&&":
return 5;
// no default
}
/* falls through */
case "BinaryExpression":
switch (node.operator) {
case "|":
return 6;
case "^":
return 7;
case "&":
return 8;
case "==":
case "!=":
case "===":
case "!==":
return 9;
case "<":
case "<=":
case ">":
case ">=":
case "in":
case "instanceof":
return 10;
case "<<":
case ">>":
case ">>>":
return 11;
case "+":
case "-":
return 12;
case "*":
case "/":
case "%":
return 13;
case "**":
return 15;
// no default
}
/* falls through */
case "UnaryExpression":
case "AwaitExpression":
return 16;
case "UpdateExpression":
return 17;
case "CallExpression":
case "ChainExpression":
case "ImportExpression":
return 18;
case "NewExpression":
return 19;
default:
if (node.type in eslintVisitorKeys) {
return 20;
}
/*
* if the node is not a standard node that we know about, then assume it has the lowest precedence
* this will mean that rules will wrap unknown nodes in parentheses where applicable instead of
* unwrapping them and potentially changing the meaning of the code or introducing a syntax error.
*/
return -1;
}
},
/**
* Checks whether the given node is an empty block node or not.
* @param {ASTNode|null} node The node to check.
* @returns {boolean} `true` if the node is an empty block.
*/
isEmptyBlock(node) {
return Boolean(
node && node.type === "BlockStatement" && node.body.length === 0,
);
},
/**
* Checks whether the given node is an empty function node or not.
* @param {ASTNode|null} node The node to check.
* @returns {boolean} `true` if the node is an empty function.
*/
isEmptyFunction(node) {
return isFunction(node) && module.exports.isEmptyBlock(node.body);
},
/**
* Get directives from directive prologue of a Program or Function node.
* @param {ASTNode} node The node to check.
* @returns {ASTNode[]} The directives found in the directive prologue.
*/
getDirectivePrologue(node) {
const directives = [];
// Directive prologues only occur at the top of files or functions.
if (
node.type === "Program" ||
node.type === "FunctionDeclaration" ||
node.type === "FunctionExpression" ||
/*
* Do not check arrow functions with implicit return.
* `() => "use strict";` returns the string `"use strict"`.
*/
(node.type === "ArrowFunctionExpression" &&
node.body.type === "BlockStatement")
) {
const statements =
node.type === "Program" ? node.body : node.body.body;
for (const statement of statements) {
if (
statement.type === "ExpressionStatement" &&
statement.expression.type === "Literal"
) {
directives.push(statement);
} else {
break;
}
}
}
return directives;
},
/**
* Determines whether this node is a decimal integer literal. If a node is a decimal integer literal, a dot added
* after the node will be parsed as a decimal point, rather than a property-access dot.
* @param {ASTNode} node The node to check.
* @returns {boolean} `true` if this node is a decimal integer.
* @example
*
* 0 // true
* 5 // true
* 50 // true
* 5_000 // true
* 1_234_56 // true
* 08 // true
* 0192 // true
* 5. // false
* .5 // false
* 5.0 // false
* 5.00_00 // false
* 05 // false
* 0x5 // false
* 0b101 // false
* 0b11_01 // false
* 0o5 // false
* 5e0 // false
* 5e1_000 // false
* 5n // false
* 1_000n // false
* "5" // false
*
*/
isDecimalInteger(node) {
return (
node.type === "Literal" &&
typeof node.value === "number" &&
DECIMAL_INTEGER_PATTERN.test(node.raw)
);
},
/**
* Determines whether this token is a decimal integer numeric token.
* This is similar to isDecimalInteger(), but for tokens.
* @param {Token} token The token to check.
* @returns {boolean} `true` if this token is a decimal integer.
*/
isDecimalIntegerNumericToken(token) {
return (
token.type === "Numeric" &&
DECIMAL_INTEGER_PATTERN.test(token.value)
);
},
/**
* Gets the name and kind of the given function node.
*
* - `function foo() {}` .................... `function 'foo'`
* - `(function foo() {})` .................. `function 'foo'`
* - `(function() {})` ...................... `function`
* - `function* foo() {}` ................... `generator function 'foo'`
* - `(function* foo() {})` ................. `generator function 'foo'`
* - `(function*() {})` ..................... `generator function`
* - `() => {}` ............................. `arrow function`
* - `async () => {}` ....................... `async arrow function`
* - `({ foo: function foo() {} })` ......... `method 'foo'`
* - `({ foo: function() {} })` ............. `method 'foo'`
* - `({ ['foo']: function() {} })` ......... `method 'foo'`
* - `({ [foo]: function() {} })` ........... `method`
* - `({ foo() {} })` ....................... `method 'foo'`
* - `({ foo: function* foo() {} })` ........ `generator method 'foo'`
* - `({ foo: function*() {} })` ............ `generator method 'foo'`
* - `({ ['foo']: function*() {} })` ........ `generator method 'foo'`
* - `({ [foo]: function*() {} })` .......... `generator method`
* - `({ *foo() {} })` ...................... `generator method 'foo'`
* - `({ foo: async function foo() {} })` ... `async method 'foo'`
* - `({ foo: async function() {} })` ....... `async method 'foo'`
* - `({ ['foo']: async function() {} })` ... `async method 'foo'`
* - `({ [foo]: async function() {} })` ..... `async method`
* - `({ async foo() {} })` ................. `async method 'foo'`
* - `({ get foo() {} })` ................... `getter 'foo'`
* - `({ set foo(a) {} })` .................. `setter 'foo'`
* - `class A { constructor() {} }` ......... `constructor`
* - `class A { foo() {} }` ................. `method 'foo'`
* - `class A { *foo() {} }` ................ `generator method 'foo'`
* - `class A { async foo() {} }` ........... `async method 'foo'`
* - `class A { ['foo']() {} }` ............. `method 'foo'`
* - `class A { *['foo']() {} }` ............ `generator method 'foo'`
* - `class A { async ['foo']() {} }` ....... `async method 'foo'`
* - `class A { [foo]() {} }` ............... `method`
* - `class A { *[foo]() {} }` .............. `generator method`
* - `class A { async [foo]() {} }` ......... `async method`
* - `class A { get foo() {} }` ............. `getter 'foo'`
* - `class A { set foo(a) {} }` ............ `setter 'foo'`
* - `class A { static foo() {} }` .......... `static method 'foo'`
* - `class A { static *foo() {} }` ......... `static generator method 'foo'`
* - `class A { static async foo() {} }` .... `static async method 'foo'`
* - `class A { static get foo() {} }` ...... `static getter 'foo'`
* - `class A { static set foo(a) {} }` ..... `static setter 'foo'`
* - `class A { foo = () => {}; }` .......... `method 'foo'`
* - `class A { foo = function() {}; }` ..... `method 'foo'`
* - `class A { foo = function bar() {}; }` . `method 'foo'`
* - `class A { static foo = () => {}; }` ... `static method 'foo'`
* - `class A { '#foo' = () => {}; }` ....... `method '#foo'`
* - `class A { #foo = () => {}; }` ......... `private method #foo`
* - `class A { static #foo = () => {}; }` .. `static private method #foo`
* - `class A { '#foo'() {} }` .............. `method '#foo'`
* - `class A { #foo() {} }` ................ `private method #foo`
* - `class A { static #foo() {} }` ......... `static private method #foo`
* @param {ASTNode} node The function node to get.
* @returns {string} The name and kind of the function node.
*/
getFunctionNameWithKind(node) {
const parent = node.parent;
const tokens = [];
if (
parent.type === "MethodDefinition" ||
parent.type === "PropertyDefinition" ||
node.type === "TSPropertySignature" ||
node.type === "TSMethodSignature"
) {
// The proposal uses `static` word consistently before visibility words: https://github.com/tc39/proposal-static-class-features
if (parent.static) {
tokens.push("static");
}
if (!parent.computed && parent.key?.type === "PrivateIdentifier") {
tokens.push("private");
}
}
if (node.async) {
tokens.push("async");
}
if (node.generator) {
tokens.push("generator");
}
if (parent.type === "Property" || parent.type === "MethodDefinition") {
if (parent.kind === "constructor") {
return "constructor";
}
if (parent.kind === "get") {
tokens.push("getter");
} else if (parent.kind === "set") {
tokens.push("setter");
} else {
tokens.push("method");
}
} else if (node.type === "TSMethodSignature") {
if (node.kind === "get") {
tokens.push("getter");
} else if (node.kind === "set") {
tokens.push("setter");
} else {
tokens.push("method");
}
} else if (parent.type === "PropertyDefinition") {
tokens.push("method");
} else {
if (node.type === "ArrowFunctionExpression") {
tokens.push("arrow");
}
tokens.push("function");
}
if (
parent.type === "Property" ||
parent.type === "MethodDefinition" ||
parent.type === "PropertyDefinition"
) {
if (!parent.computed && parent.key.type === "PrivateIdentifier") {
tokens.push(`#${parent.key.name}`);
} else {
const name = getStaticPropertyName(parent);
if (name !== null) {
tokens.push(`'${name}'`);
} else if (node.id) {
tokens.push(`'${node.id.name}'`);
}
}
} else if (node.type === "TSMethodSignature") {
tokens.push(`'${getStaticPropertyName(node)}'`);
} else if (node.id) {
tokens.push(`'${node.id.name}'`);
}
return tokens.join(" ");
},
/**
* Gets the location of the given function node for reporting.
*
* - `function foo() {}`
* ^^^^^^^^^^^^
* - `(function foo() {})`
* ^^^^^^^^^^^^
* - `(function() {})`
* ^^^^^^^^
* - `function* foo() {}`
* ^^^^^^^^^^^^^
* - `(function* foo() {})`
* ^^^^^^^^^^^^^
* - `(function*() {})`
* ^^^^^^^^^
* - `() => {}`
* ^^
* - `async () => {}`
* ^^
* - `({ foo: function foo() {} })`
* ^^^^^^^^^^^^^^^^^
* - `({ foo: function() {} })`
* ^^^^^^^^^^^^^
* - `({ ['foo']: function() {} })`
* ^^^^^^^^^^^^^^^^^
* - `({ [foo]: function() {} })`
* ^^^^^^^^^^^^^^^
* - `({ foo() {} })`
* ^^^
* - `({ foo: function* foo() {} })`
* ^^^^^^^^^^^^^^^^^^
* - `({ foo: function*() {} })`
* ^^^^^^^^^^^^^^
* - `({ ['foo']: function*() {} })`
* ^^^^^^^^^^^^^^^^^^
* - `({ [foo]: function*() {} })`
* ^^^^^^^^^^^^^^^^
* - `({ *foo() {} })`
* ^^^^
* - `({ foo: async function foo() {} })`
* ^^^^^^^^^^^^^^^^^^^^^^^
* - `({ foo: async function() {} })`
* ^^^^^^^^^^^^^^^^^^^
* - `({ ['foo']: async function() {} })`
* ^^^^^^^^^^^^^^^^^^^^^^^
* - `({ [foo]: async function() {} })`
* ^^^^^^^^^^^^^^^^^^^^^
* - `({ async foo() {} })`
* ^^^^^^^^^
* - `({ get foo() {} })`
* ^^^^^^^
* - `({ set foo(a) {} })`
* ^^^^^^^
* - `class A { constructor() {} }`
* ^^^^^^^^^^^
* - `class A { foo() {} }`
* ^^^
* - `class A { *foo() {} }`
* ^^^^
* - `class A { async foo() {} }`
* ^^^^^^^^^
* - `class A { ['foo']() {} }`
* ^^^^^^^
* - `class A { *['foo']() {} }`
* ^^^^^^^^
* - `class A { async ['foo']() {} }`
* ^^^^^^^^^^^^^
* - `class A { [foo]() {} }`
* ^^^^^
* - `class A { *[foo]() {} }`
* ^^^^^^
* - `class A { async [foo]() {} }`
* ^^^^^^^^^^^
* - `class A { get foo() {} }`
* ^^^^^^^
* - `class A { set foo(a) {} }`
* ^^^^^^^
* - `class A { static foo() {} }`
* ^^^^^^^^^^
* - `class A { static *foo() {} }`
* ^^^^^^^^^^^
* - `class A { static async foo() {} }`
* ^^^^^^^^^^^^^^^^
* - `class A { static get foo() {} }`
* ^^^^^^^^^^^^^^
* - `class A { static set foo(a) {} }`
* ^^^^^^^^^^^^^^
* - `class A { foo = function() {} }`
* ^^^^^^^^^^^^^^
* - `class A { static foo = function() {} }`
* ^^^^^^^^^^^^^^^^^^^^^
* - `class A { foo = (a, b) => {} }`
* ^^^^^^
* @param {ASTNode} node The function node to get.
* @param {SourceCode} sourceCode The source code object to get tokens.
* @returns {string} The location of the function node for reporting.
*/
getFunctionHeadLoc(node, sourceCode) {
const parent = node.parent;
let start;
let end;
if (
parent.type === "Property" ||
parent.type === "MethodDefinition" ||
parent.type === "PropertyDefinition" ||
parent.type === "TSPropertySignature" ||
parent.type === "TSMethodSignature"
) {
start = parent.loc.start;
end = getOpeningParenOfParams(node, sourceCode).loc.start;
} else if (node.type === "ArrowFunctionExpression") {
const arrowToken = sourceCode.getTokenBefore(
node.body,
isArrowToken,
);
start = arrowToken.loc.start;
end = arrowToken.loc.end;
} else {
start = node.loc.start;
end = getOpeningParenOfParams(node, sourceCode).loc.start;
}
return {
start: Object.assign({}, start),
end: Object.assign({}, end),
};
},
/**
* Gets next location when the result is not out of bound, otherwise returns null.
*
* Assumptions:
*
* - The given location represents a valid location in the given source code.
* - Columns are 0-based.
* - Lines are 1-based.
* - Column immediately after the last character in a line (not incl. linebreaks) is considered to be a valid location.
* - If the source code ends with a linebreak, `sourceCode.lines` array will have an extra element (empty string) at the end.
* The start (column 0) of that extra line is considered to be a valid location.
*
* Examples of successive locations (line, column):
*
* code: foo
* locations: (1, 0) -> (1, 1) -> (1, 2) -> (1, 3) -> null
*
* code: foo<LF>
* locations: (1, 0) -> (1, 1) -> (1, 2) -> (1, 3) -> (2, 0) -> null
*
* code: foo<CR><LF>
* locations: (1, 0) -> (1, 1) -> (1, 2) -> (1, 3) -> (2, 0) -> null
*
* code: a<LF>b
* locations: (1, 0) -> (1, 1) -> (2, 0) -> (2, 1) -> null
*
* code: a<LF>b<LF>
* locations: (1, 0) -> (1, 1) -> (2, 0) -> (2, 1) -> (3, 0) -> null
*
* code: a<CR><LF>b<CR><LF>
* locations: (1, 0) -> (1, 1) -> (2, 0) -> (2, 1) -> (3, 0) -> null
*
* code: a<LF><LF>
* locations: (1, 0) -> (1, 1) -> (2, 0) -> (3, 0) -> null
*
* code: <LF>
* locations: (1, 0) -> (2, 0) -> null
*
* code:
* locations: (1, 0) -> null
* @param {SourceCode} sourceCode The sourceCode
* @param {{line: number, column: number}} location The location
* @returns {{line: number, column: number} | null} Next location
*/
getNextLocation(sourceCode, { line, column }) {
if (column < sourceCode.lines[line - 1].length) {
return {
line,
column: column + 1,
};
}
if (line < sourceCode.lines.length) {
return {
line: line + 1,
column: 0,
};
}
return null;
},
/**
* Gets the parenthesized text of a node. This is similar to sourceCode.getText(node), but it also includes any parentheses
* surrounding the node.
* @param {SourceCode} sourceCode The source code object
* @param {ASTNode} node An expression node
* @returns {string} The text representing the node, with all surrounding parentheses included
*/
getParenthesisedText(sourceCode, node) {
let leftToken = sourceCode.getFirstToken(node);
let rightToken = sourceCode.getLastToken(node);
while (
sourceCode.getTokenBefore(leftToken) &&
sourceCode.getTokenBefore(leftToken).type === "Punctuator" &&
sourceCode.getTokenBefore(leftToken).value === "(" &&
sourceCode.getTokenAfter(rightToken) &&
sourceCode.getTokenAfter(rightToken).type === "Punctuator" &&
sourceCode.getTokenAfter(rightToken).value === ")"
) {
leftToken = sourceCode.getTokenBefore(leftToken);
rightToken = sourceCode.getTokenAfter(rightToken);
}
return sourceCode
.getText()
.slice(leftToken.range[0], rightToken.range[1]);
},
/**
* Determine if a node has a possibility to be an Error object
* @param {ASTNode} node ASTNode to check
* @returns {boolean} True if there is a chance it contains an Error obj
*/
couldBeError(node) {
switch (node.type) {
case "Identifier":
case "CallExpression":
case "NewExpression":
case "MemberExpression":
case "TaggedTemplateExpression":
case "YieldExpression":
case "AwaitExpression":
case "ChainExpression":
return true; // possibly an error object.
case "AssignmentExpression":
if (["=", "&&="].includes(node.operator)) {
return module.exports.couldBeError(node.right);
}
if (["||=", "??="].includes(node.operator)) {
return (
module.exports.couldBeError(node.left) ||
module.exports.couldBeError(node.right)
);
}
/**
* All other assignment operators are mathematical assignment operators (arithmetic or bitwise).
* An assignment expression with a mathematical operator can either evaluate to a primitive value,
* or throw, depending on the operands. Thus, it cannot evaluate to an `Error` object.
*/
return false;
case "SequenceExpression": {
const exprs = node.expressions;
return (
exprs.length !== 0 &&
module.exports.couldBeError(exprs.at(-1))
);
}
case "LogicalExpression":
/*
* If the && operator short-circuits, the left side was falsy and therefore not an error, and if it
* doesn't short-circuit, it takes the value from the right side, so the right side must always be
* a plausible error. A future improvement could verify that the left side could be truthy by
* excluding falsy literals.
*/
if (node.operator === "&&") {
return module.exports.couldBeError(node.right);
}
return (
module.exports.couldBeError(node.left) ||
module.exports.couldBeError(node.right)
);
case "ConditionalExpression":
return (
module.exports.couldBeError(node.consequent) ||
module.exports.couldBeError(node.alternate)
);
default:
return false;
}
},
/**
* Check if a given node is a numeric literal or not.
* @param {ASTNode} node The node to check.
* @returns {boolean} `true` if the node is a number or bigint literal.
*/
isNumericLiteral(node) {
return (
node.type === "Literal" &&
(typeof node.value === "number" || Boolean(node.bigint))
);
},
/**
* Determines whether two tokens can safely be placed next to each other without merging into a single token
* @param {Token|string} leftValue The left token. If this is a string, it will be tokenized and the last token will be used.
* @param {Token|string} rightValue The right token. If this is a string, it will be tokenized and the first token will be used.
* @returns {boolean} If the tokens cannot be safely placed next to each other, returns `false`. If the tokens can be placed
* next to each other, behavior is undefined (although it should return `true` in most cases).
*/
canTokensBeAdjacent(leftValue, rightValue) {
const espreeOptions = {
ecmaVersion: espree.latestEcmaVersion,
comment: true,
range: true,
};
let leftToken;
if (typeof leftValue === "string") {
let tokens;
try {
tokens = espree.tokenize(leftValue, espreeOptions);
} catch {
return false;
}
const comments = tokens.comments;
leftToken = tokens.at(-1);
if (comments.length) {
const lastComment = comments.at(-1);
if (!leftToken || lastComment.range[0] > leftToken.range[0]) {
leftToken = lastComment;
}
}
} else {
leftToken = leftValue;
}
/*
* If a hashbang comment was passed as a token object from SourceCode,
* its type will be "Shebang" because of the way ESLint itself handles hashbangs.
* If a hashbang comment was passed in a string and then tokenized in this function,
* its type will be "Hashbang" because of the way Espree tokenizes hashbangs.
*/
if (leftToken.type === "Shebang" || leftToken.type === "Hashbang") {
return false;
}
let rightToken;
if (typeof rightValue === "string") {
let tokens;
try {
tokens = espree.tokenize(rightValue, espreeOptions);
} catch {
return false;
}
const comments = tokens.comments;
rightToken = tokens[0];
if (comments.length) {
const firstComment = comments[0];
if (
!rightToken ||
firstComment.range[0] < rightToken.range[0]
) {
rightToken = firstComment;
}
}
} else {
rightToken = rightValue;
}
if (
leftToken.type === "Punctuator" ||
rightToken.type === "Punctuator"
) {
if (
leftToken.type === "Punctuator" &&
rightToken.type === "Punctuator"
) {
const PLUS_TOKENS = new Set(["+", "++"]);
const MINUS_TOKENS = new Set(["-", "--"]);
return !(
(PLUS_TOKENS.has(leftToken.value) &&
PLUS_TOKENS.has(rightToken.value)) ||
(MINUS_TOKENS.has(leftToken.value) &&
MINUS_TOKENS.has(rightToken.value))
);
}
if (leftToken.type === "Punctuator" && leftToken.value === "/") {
return !["Block", "Line", "RegularExpression"].includes(
rightToken.type,
);
}
return true;
}
if (
leftToken.type === "String" ||
rightToken.type === "String" ||
leftToken.type === "Template" ||
rightToken.type === "Template"
) {
return true;
}
if (
leftToken.type !== "Numeric" &&
rightToken.type === "Numeric" &&
rightToken.value.startsWith(".")
) {
return true;
}
if (
leftToken.type === "Block" ||
rightToken.type === "Block" ||
rightToken.type === "Line"
) {
return true;
}
if (rightToken.type === "PrivateIdentifier") {
return true;
}
return false;
},
/**
* Get the `loc` object of a given name in a `/*globals` directive comment.
* @param {SourceCode} sourceCode The source code to convert index to loc.
* @param {Comment} comment The `/*globals` directive comment which include the name.
* @param {string} name The name to find.
* @returns {SourceLocation} The `loc` object.
*/
getNameLocationInGlobalDirectiveComment(sourceCode, comment, name) {
const namePattern = new RegExp(
`[\\s,]${escapeRegExp(name)}(?:$|[\\s,:])`,
"gu",
);
// To ignore the first text "global".
namePattern.lastIndex = comment.value.indexOf("global") + 6;
// Search a given variable name.
const match = namePattern.exec(comment.value);
// Convert the index to loc.
const start = sourceCode.getLocFromIndex(
comment.range[0] + "/*".length + (match ? match.index + 1 : 0),
);
const end = {
line: start.line,
column: start.column + (match ? name.length : 1),
};
return { start, end };
},
/**
* Determines whether the given raw string contains an octal escape sequence
* or a non-octal decimal escape sequence ("\8", "\9").
*
* "\1", "\2" ... "\7", "\8", "\9"
* "\00", "\01" ... "\07", "\08", "\09"
*
* "\0", when not followed by a digit, is not an octal escape sequence.
* @param {string} rawString A string in its raw representation.
* @returns {boolean} `true` if the string contains at least one octal escape sequence
* or at least one non-octal decimal escape sequence.
*/
hasOctalOrNonOctalDecimalEscapeSequence(rawString) {
return OCTAL_OR_NON_OCTAL_DECIMAL_ESCAPE_PATTERN.test(rawString);
},
/**
* Determines whether the given node is a template literal without expressions.
* @param {ASTNode} node Node to check.
* @returns {boolean} True if the node is a template literal without expressions.
*/
isStaticTemplateLiteral(node) {
return node.type === "TemplateLiteral" && node.expressions.length === 0;
},
/**
* Determines whether the existing curly braces around the single statement are necessary to preserve the semantics of the code.
* The braces, which make the given block body, are necessary in either of the following situations:
*
* 1. The statement is a lexical declaration.
* 2. Without the braces, an `if` within the statement would become associated with an `else` after the closing brace:
*
* if (a) {
* if (b)
* foo();
* }
* else
* bar();
*
* if (a)
* while (b)
* while (c) {
* while (d)
* if (e)
* while(f)
* foo();
* }
* else
* bar();
* @param {ASTNode} node `BlockStatement` body with exactly one statement directly inside. The statement can have its own nested statements.
* @param {SourceCode} sourceCode The source code
* @returns {boolean} `true` if the braces are necessary - removing them (replacing the given `BlockStatement` body with its single statement content)
* would change the semantics of the code or produce a syntax error.
*/
areBracesNecessary(node, sourceCode) {
/**
* Determines if the given node is a lexical declaration (let, const, using, await using, function, or class)
* @param {ASTNode} nodeToCheck The node to check
* @returns {boolean} True if the node is a lexical declaration
* @private
*/
function isLexicalDeclaration(nodeToCheck) {
if (nodeToCheck.type === "VariableDeclaration") {
return LEXICAL_DECLARATION_KINDS.has(nodeToCheck.kind);
}
return (
nodeToCheck.type === "FunctionDeclaration" ||
nodeToCheck.type === "ClassDeclaration"
);
}
/**
* Checks if the given token is an `else` token or not.
* @param {Token} token The token to check.
* @returns {boolean} `true` if the token is an `else` token.
*/
function isElseKeywordToken(token) {
return token.value === "else" && token.type === "Keyword";
}
/**
* Determines whether the given node has an `else` keyword token as the first token after.
* @param {ASTNode} nodeToCheck The node to check.
* @returns {boolean} `true` if the node is followed by an `else` keyword token.
*/
function isFollowedByElseKeyword(nodeToCheck) {
const nextToken = sourceCode.getTokenAfter(nodeToCheck);
return Boolean(nextToken) && isElseKeywordToken(nextToken);
}
/**
* Determines whether the code represented by the given node contains an `if` statement
* that would become associated with an `else` keyword directly appended to that code.
*
* Examples where it returns `true`:
*
* if (a)
* foo();
*
* if (a) {
* foo();
* }
*
* if (a)
* foo();
* else if (b)
* bar();
*
* while (a)
* if (b)
* if(c)
* foo();
* else
* bar();
*
* Examples where it returns `false`:
*
* if (a)
* foo();
* else
* bar();
*
* while (a) {
* if (b)
* if(c)
* foo();
* else
* bar();
* }
*
* while (a)
* if (b) {
* if(c)
* foo();
* }
* else
* bar();
* @param {ASTNode} nodeToCheck Node representing the code to check.
* @returns {boolean} `true` if an `if` statement within the code would become associated with an `else` appended to that code.
*/
function hasUnsafeIf(nodeToCheck) {
switch (nodeToCheck.type) {
case "IfStatement":
if (!nodeToCheck.alternate) {
return true;
}
return hasUnsafeIf(nodeToCheck.alternate);
case "ForStatement":
case "ForInStatement":
case "ForOfStatement":
case "LabeledStatement":
case "WithStatement":
case "WhileStatement":
return hasUnsafeIf(nodeToCheck.body);
default:
return false;
}
}
const statement = node.body[0];
return (
isLexicalDeclaration(statement) ||
(hasUnsafeIf(statement) && isFollowedByElseKeyword(node))
);
},
isReferenceToGlobalVariable,
isLogicalExpression,
isCoalesceExpression,
isMixedLogicalAndCoalesceExpressions,
isNullLiteral,
getStaticStringValue,
getStaticPropertyName,
skipChainExpression,
isSpecificId,
isSpecificMemberAccess,
equalLiteralValue,
isSameReference,
isLogicalAssignmentOperator,
getSwitchCaseColonToken,
getModuleExportName,
isConstant,
isTopLevelExpressionStatement,
isDirective,
isStartOfExpressionStatement,
needsPrecedingSemicolon,
isImportAttributeKey,
getOpeningParenOfParams,
};