/home/techb158/balavpn.abdallabala.com/node_modules/eslint/lib/rules
Edit: /home/techb158/balavpn.abdallabala.com/node_modules/eslint/lib/rules/prefer-template.js (10537B)
/**
* @fileoverview A rule to suggest using template literals instead of string concatenation.
* @author Toru Nagashima
*/
"use strict";
//------------------------------------------------------------------------------
// Requirements
//------------------------------------------------------------------------------
const astUtils = require("./utils/ast-utils");
//------------------------------------------------------------------------------
// Helpers
//------------------------------------------------------------------------------
/**
* Checks whether or not a given node is a concatenation.
* @param {ASTNode} node A node to check.
* @returns {boolean} `true` if the node is a concatenation.
*/
function isConcatenation(node) {
return node.type === "BinaryExpression" && node.operator === "+";
}
/**
* Gets the top binary expression node for concatenation in parents of a given node.
* @param {ASTNode} node A node to get.
* @returns {ASTNode} the top binary expression node in parents of a given node.
*/
function getTopConcatBinaryExpression(node) {
let currentNode = node;
while (isConcatenation(currentNode.parent)) {
currentNode = currentNode.parent;
}
return currentNode;
}
/**
* Checks whether or not a node contains a string literal with an octal or non-octal decimal escape sequence
* @param {ASTNode} node A node to check
* @returns {boolean} `true` if at least one string literal within the node contains
* an octal or non-octal decimal escape sequence
*/
function hasOctalOrNonOctalDecimalEscapeSequence(node) {
if (isConcatenation(node)) {
return (
hasOctalOrNonOctalDecimalEscapeSequence(node.left) ||
hasOctalOrNonOctalDecimalEscapeSequence(node.right)
);
}
// No need to check TemplateLiterals – would throw parsing error
if (node.type === "Literal" && typeof node.value === "string") {
return astUtils.hasOctalOrNonOctalDecimalEscapeSequence(node.raw);
}
return false;
}
/**
* Checks whether or not a given binary expression has string literals.
* @param {ASTNode} node A node to check.
* @returns {boolean} `true` if the node has string literals.
*/
function hasStringLiteral(node) {
if (isConcatenation(node)) {
// `left` is deeper than `right` normally.
return hasStringLiteral(node.right) || hasStringLiteral(node.left);
}
return astUtils.isStringLiteral(node);
}
/**
* Checks whether or not a given binary expression has non string literals.
* @param {ASTNode} node A node to check.
* @returns {boolean} `true` if the node has non string literals.
*/
function hasNonStringLiteral(node) {
if (isConcatenation(node)) {
// `left` is deeper than `right` normally.
return (
hasNonStringLiteral(node.right) || hasNonStringLiteral(node.left)
);
}
return !astUtils.isStringLiteral(node);
}
/**
* Determines whether a given node will start with a template curly expression (`${}`) when being converted to a template literal.
* @param {ASTNode} node The node that will be fixed to a template literal
* @returns {boolean} `true` if the node will start with a template curly.
*/
function startsWithTemplateCurly(node) {
if (node.type === "BinaryExpression") {
return startsWithTemplateCurly(node.left);
}
if (node.type === "TemplateLiteral") {
return (
node.expressions.length &&
node.quasis.length &&
node.quasis[0].range[0] === node.quasis[0].range[1]
);
}
return node.type !== "Literal" || typeof node.value !== "string";
}
/**
* Determines whether a given node end with a template curly expression (`${}`) when being converted to a template literal.
* @param {ASTNode} node The node that will be fixed to a template literal
* @returns {boolean} `true` if the node will end with a template curly.
*/
function endsWithTemplateCurly(node) {
if (node.type === "BinaryExpression") {
return startsWithTemplateCurly(node.right);
}
if (node.type === "TemplateLiteral") {
return (
node.expressions.length &&
node.quasis.length &&
node.quasis.at(-1).range[0] === node.quasis.at(-1).range[1]
);
}
return node.type !== "Literal" || typeof node.value !== "string";
}
//------------------------------------------------------------------------------
// Rule Definition
//------------------------------------------------------------------------------
/** @type {import('../types').Rule.RuleModule} */
module.exports = {
meta: {
type: "suggestion",
docs: {
description:
"Require template literals instead of string concatenation",
recommended: false,
frozen: true,
url: "https://eslint.org/docs/latest/rules/prefer-template",
},
schema: [],
fixable: "code",
messages: {
unexpectedStringConcatenation: "Unexpected string concatenation.",
},
},
create(context) {
const sourceCode = context.sourceCode;
let done = Object.create(null);
/**
* Gets the non-token text between two nodes, ignoring any other tokens that appear between the two tokens.
* @param {ASTNode} node1 The first node
* @param {ASTNode} node2 The second node
* @returns {string} The text between the nodes, excluding other tokens
*/
function getTextBetween(node1, node2) {
const allTokens = [node1]
.concat(sourceCode.getTokensBetween(node1, node2))
.concat(node2);
const sourceText = sourceCode.getText();
return allTokens
.slice(0, -1)
.reduce(
(accumulator, token, index) =>
accumulator +
sourceText.slice(
token.range[1],
allTokens[index + 1].range[0],
),
"",
);
}
/**
* Returns a template literal form of the given node.
* @param {ASTNode} currentNode A node that should be converted to a template literal
* @param {string} textBeforeNode Text that should appear before the node
* @param {string} textAfterNode Text that should appear after the node
* @returns {string} A string form of this node, represented as a template literal
*/
function getTemplateLiteral(
currentNode,
textBeforeNode,
textAfterNode,
) {
if (
currentNode.type === "Literal" &&
typeof currentNode.value === "string"
) {
/*
* If the current node is a string literal, escape any instances of ${ or ` to prevent them from being interpreted
* as a template placeholder. However, if the code already contains a backslash before the ${ or `
* for some reason, don't add another backslash, because that would change the meaning of the code (it would cause
* an actual backslash character to appear before the dollar sign).
*/
return `\`${currentNode.raw
.slice(1, -1)
.replace(/\\*(\$\{|`)/gu, matched => {
if (matched.lastIndexOf("\\") % 2) {
return `\\${matched}`;
}
return matched;
// Unescape any quotes that appear in the original Literal that no longer need to be escaped.
})
.replace(
new RegExp(`\\\\${currentNode.raw[0]}`, "gu"),
currentNode.raw[0],
)}\``;
}
if (currentNode.type === "TemplateLiteral") {
return sourceCode.getText(currentNode);
}
if (isConcatenation(currentNode) && hasStringLiteral(currentNode)) {
const plusSign = sourceCode.getFirstTokenBetween(
currentNode.left,
currentNode.right,
token => token.value === "+",
);
const textBeforePlus = getTextBetween(
currentNode.left,
plusSign,
);
const textAfterPlus = getTextBetween(
plusSign,
currentNode.right,
);
const leftEndsWithCurly = endsWithTemplateCurly(
currentNode.left,
);
const rightStartsWithCurly = startsWithTemplateCurly(
currentNode.right,
);
if (leftEndsWithCurly) {
// If the left side of the expression ends with a template curly, add the extra text to the end of the curly bracket.
// `foo${bar}` /* comment */ + 'baz' --> `foo${bar /* comment */ }${baz}`
return (
getTemplateLiteral(
currentNode.left,
textBeforeNode,
textBeforePlus + textAfterPlus,
).slice(0, -1) +
getTemplateLiteral(
currentNode.right,
null,
textAfterNode,
).slice(1)
);
}
if (rightStartsWithCurly) {
// Otherwise, if the right side of the expression starts with a template curly, add the text there.
// 'foo' /* comment */ + `${bar}baz` --> `foo${ /* comment */ bar}baz`
return (
getTemplateLiteral(
currentNode.left,
textBeforeNode,
null,
).slice(0, -1) +
getTemplateLiteral(
currentNode.right,
textBeforePlus + textAfterPlus,
textAfterNode,
).slice(1)
);
}
/*
* Otherwise, these nodes should not be combined into a template curly, since there is nowhere to put
* the text between them.
*/
return `${getTemplateLiteral(currentNode.left, textBeforeNode, null)}${textBeforePlus}+${textAfterPlus}${getTemplateLiteral(currentNode.right, textAfterNode, null)}`;
}
return `\`\${${textBeforeNode || ""}${sourceCode.getText(currentNode)}${textAfterNode || ""}}\``;
}
/**
* Returns a fixer object that converts a non-string binary expression to a template literal
* @param {SourceCodeFixer} fixer The fixer object
* @param {ASTNode} node A node that should be converted to a template literal
* @returns {Object} A fix for this binary expression
*/
function fixNonStringBinaryExpression(fixer, node) {
const topBinaryExpr = getTopConcatBinaryExpression(node.parent);
if (hasOctalOrNonOctalDecimalEscapeSequence(topBinaryExpr)) {
return null;
}
return fixer.replaceText(
topBinaryExpr,
getTemplateLiteral(topBinaryExpr, null, null),
);
}
/**
* Reports if a given node is string concatenation with non string literals.
* @param {ASTNode} node A node to check.
* @returns {void}
*/
function checkForStringConcat(node) {
if (
!astUtils.isStringLiteral(node) ||
!isConcatenation(node.parent)
) {
return;
}
const topBinaryExpr = getTopConcatBinaryExpression(node.parent);
// Checks whether or not this node had been checked already.
if (done[topBinaryExpr.range[0]]) {
return;
}
done[topBinaryExpr.range[0]] = true;
if (hasNonStringLiteral(topBinaryExpr)) {
context.report({
node: topBinaryExpr,
messageId: "unexpectedStringConcatenation",
fix: fixer => fixNonStringBinaryExpression(fixer, node),
});
}
}
return {
Program() {
done = Object.create(null);
},
Literal: checkForStringConcat,
TemplateLiteral: checkForStringConcat,
};
},
};