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/**
* @fileoverview Rule to disallow if as the only statement in an else block
* @author Brandon Mills
*/
"use strict";
//------------------------------------------------------------------------------
// Requirements
//------------------------------------------------------------------------------
const astUtils = require("./utils/ast-utils");
//------------------------------------------------------------------------------
// Rule Definition
//------------------------------------------------------------------------------
/** @type {import('../types').Rule.RuleModule} */
module.exports = {
meta: {
type: "suggestion",
docs: {
description:
"Disallow `if` statements as the only statement in `else` blocks",
recommended: false,
frozen: true,
url: "https://eslint.org/docs/latest/rules/no-lonely-if",
},
schema: [],
fixable: "code",
messages: {
unexpectedLonelyIf:
"Unexpected if as the only statement in an else block.",
},
},
create(context) {
const sourceCode = context.sourceCode;
return {
IfStatement(node) {
const parent = node.parent,
grandparent = parent.parent;
if (
parent &&
parent.type === "BlockStatement" &&
parent.body.length === 1 &&
!astUtils.areBracesNecessary(parent, sourceCode) &&
grandparent &&
grandparent.type === "IfStatement" &&
parent === grandparent.alternate
) {
context.report({
node,
messageId: "unexpectedLonelyIf",
fix(fixer) {
const openingElseCurly =
sourceCode.getFirstToken(parent);
const closingElseCurly =
sourceCode.getLastToken(parent);
const elseKeyword =
sourceCode.getTokenBefore(openingElseCurly);
const tokenAfterElseBlock =
sourceCode.getTokenAfter(closingElseCurly);
const lastIfToken = sourceCode.getLastToken(
node.consequent,
);
const sourceText = sourceCode.getText();
if (
sourceText
.slice(
openingElseCurly.range[1],
node.range[0],
)
.trim() ||
sourceText
.slice(
node.range[1],
closingElseCurly.range[0],
)
.trim()
) {
// Don't fix if there are any non-whitespace characters interfering (e.g. comments)
return null;
}
if (
node.consequent.type !== "BlockStatement" &&
lastIfToken.value !== ";" &&
tokenAfterElseBlock &&
(node.consequent.loc.end.line ===
tokenAfterElseBlock.loc.start.line ||
/^[([/+`-]/u.test(
tokenAfterElseBlock.value,
) ||
lastIfToken.value === "++" ||
lastIfToken.value === "--")
) {
/*
* If the `if` statement has no block, and is not followed by a semicolon, make sure that fixing
* the issue would not change semantics due to ASI. If this would happen, don't do a fix.
*/
return null;
}
return fixer.replaceTextRange(
[
openingElseCurly.range[0],
closingElseCurly.range[1],
],
(elseKeyword.range[1] ===
openingElseCurly.range[0]
? " "
: "") + sourceCode.getText(node),
);
},
});
}
},
};
},
};
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