no-multiple-empty-lines.js
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/**
* @fileoverview Disallows multiple blank lines.
* implementation adapted from the no-trailing-spaces rule.
* @author Greg Cochard
*/
"use strict";
//------------------------------------------------------------------------------
// Rule Definition
//------------------------------------------------------------------------------
module.exports = {
meta: {
type: "layout",
docs: {
description: "disallow multiple empty lines",
category: "Stylistic Issues",
recommended: false,
url: "https://eslint.org/docs/rules/no-multiple-empty-lines"
},
fixable: "whitespace",
schema: [
{
type: "object",
properties: {
max: {
type: "integer",
minimum: 0
},
maxEOF: {
type: "integer",
minimum: 0
},
maxBOF: {
type: "integer",
minimum: 0
}
},
required: ["max"],
additionalProperties: false
}
],
messages: {
blankBeginningOfFile: "Too many blank lines at the beginning of file. Max of {{max}} allowed.",
blankEndOfFile: "Too many blank lines at the end of file. Max of {{max}} allowed.",
consecutiveBlank: "More than {{max}} blank {{pluralizedLines}} not allowed."
}
},
create(context) {
// Use options.max or 2 as default
let max = 2,
maxEOF = max,
maxBOF = max;
if (context.options.length) {
max = context.options[0].max;
maxEOF = typeof context.options[0].maxEOF !== "undefined" ? context.options[0].maxEOF : max;
maxBOF = typeof context.options[0].maxBOF !== "undefined" ? context.options[0].maxBOF : max;
}
const sourceCode = context.getSourceCode();
// Swallow the final newline, as some editors add it automatically and we don't want it to cause an issue
const allLines = sourceCode.lines[sourceCode.lines.length - 1] === "" ? sourceCode.lines.slice(0, -1) : sourceCode.lines;
const templateLiteralLines = new Set();
//--------------------------------------------------------------------------
// Public
//--------------------------------------------------------------------------
return {
TemplateLiteral(node) {
node.quasis.forEach(literalPart => {
// Empty lines have a semantic meaning if they're inside template literals. Don't count these as empty lines.
for (let ignoredLine = literalPart.loc.start.line; ignoredLine < literalPart.loc.end.line; ignoredLine++) {
templateLiteralLines.add(ignoredLine);
}
});
},
"Program:exit"(node) {
return allLines
// Given a list of lines, first get a list of line numbers that are non-empty.
.reduce((nonEmptyLineNumbers, line, index) => {
if (line.trim() || templateLiteralLines.has(index + 1)) {
nonEmptyLineNumbers.push(index + 1);
}
return nonEmptyLineNumbers;
}, [])
// Add a value at the end to allow trailing empty lines to be checked.
.concat(allLines.length + 1)
// Given two line numbers of non-empty lines, report the lines between if the difference is too large.
.reduce((lastLineNumber, lineNumber) => {
let messageId, maxAllowed;
if (lastLineNumber === 0) {
messageId = "blankBeginningOfFile";
maxAllowed = maxBOF;
} else if (lineNumber === allLines.length + 1) {
messageId = "blankEndOfFile";
maxAllowed = maxEOF;
} else {
messageId = "consecutiveBlank";
maxAllowed = max;
}
if (lineNumber - lastLineNumber - 1 > maxAllowed) {
context.report({
node,
loc: {
start: { line: lastLineNumber + maxAllowed + 1, column: 0 },
end: { line: lineNumber, column: 0 }
},
messageId,
data: {
max: maxAllowed,
pluralizedLines: maxAllowed === 1 ? "line" : "lines"
},
fix(fixer) {
const rangeStart = sourceCode.getIndexFromLoc({ line: lastLineNumber + 1, column: 0 });
/*
* The end of the removal range is usually the start index of the next line.
* However, at the end of the file there is no next line, so the end of the
* range is just the length of the text.
*/
const lineNumberAfterRemovedLines = lineNumber - maxAllowed;
const rangeEnd = lineNumberAfterRemovedLines <= allLines.length
? sourceCode.getIndexFromLoc({ line: lineNumberAfterRemovedLines, column: 0 })
: sourceCode.text.length;
return fixer.removeRange([rangeStart, rangeEnd]);
}
});
}
return lineNumber;
}, 0);
}
};
}
};