arrow-spacing.js
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/**
* @fileoverview Rule to define spacing before/after arrow function's arrow.
* @author Jxck
*/
"use strict";
//------------------------------------------------------------------------------
// Requirements
//------------------------------------------------------------------------------
const astUtils = require("./utils/ast-utils");
//------------------------------------------------------------------------------
// Rule Definition
//------------------------------------------------------------------------------
module.exports = {
meta: {
type: "layout",
docs: {
description: "enforce consistent spacing before and after the arrow in arrow functions",
category: "ECMAScript 6",
recommended: false,
url: "https://eslint.org/docs/rules/arrow-spacing"
},
fixable: "whitespace",
schema: [
{
type: "object",
properties: {
before: {
type: "boolean",
default: true
},
after: {
type: "boolean",
default: true
}
},
additionalProperties: false
}
],
messages: {
expectedBefore: "Missing space before =>.",
unexpectedBefore: "Unexpected space before =>.",
expectedAfter: "Missing space after =>.",
unexpectedAfter: "Unexpected space after =>."
}
},
create(context) {
// merge rules with default
const rule = Object.assign({}, context.options[0]);
rule.before = rule.before !== false;
rule.after = rule.after !== false;
const sourceCode = context.getSourceCode();
/**
* Get tokens of arrow(`=>`) and before/after arrow.
* @param {ASTNode} node The arrow function node.
* @returns {Object} Tokens of arrow and before/after arrow.
*/
function getTokens(node) {
const arrow = sourceCode.getTokenBefore(node.body, astUtils.isArrowToken);
return {
before: sourceCode.getTokenBefore(arrow),
arrow,
after: sourceCode.getTokenAfter(arrow)
};
}
/**
* Count spaces before/after arrow(`=>`) token.
* @param {Object} tokens Tokens before/after arrow.
* @returns {Object} count of space before/after arrow.
*/
function countSpaces(tokens) {
const before = tokens.arrow.range[0] - tokens.before.range[1];
const after = tokens.after.range[0] - tokens.arrow.range[1];
return { before, after };
}
/**
* Determines whether space(s) before after arrow(`=>`) is satisfy rule.
* if before/after value is `true`, there should be space(s).
* if before/after value is `false`, there should be no space.
* @param {ASTNode} node The arrow function node.
* @returns {void}
*/
function spaces(node) {
const tokens = getTokens(node);
const countSpace = countSpaces(tokens);
if (rule.before) {
// should be space(s) before arrow
if (countSpace.before === 0) {
context.report({
node: tokens.before,
messageId: "expectedBefore",
fix(fixer) {
return fixer.insertTextBefore(tokens.arrow, " ");
}
});
}
} else {
// should be no space before arrow
if (countSpace.before > 0) {
context.report({
node: tokens.before,
messageId: "unexpectedBefore",
fix(fixer) {
return fixer.removeRange([tokens.before.range[1], tokens.arrow.range[0]]);
}
});
}
}
if (rule.after) {
// should be space(s) after arrow
if (countSpace.after === 0) {
context.report({
node: tokens.after,
messageId: "expectedAfter",
fix(fixer) {
return fixer.insertTextAfter(tokens.arrow, " ");
}
});
}
} else {
// should be no space after arrow
if (countSpace.after > 0) {
context.report({
node: tokens.after,
messageId: "unexpectedAfter",
fix(fixer) {
return fixer.removeRange([tokens.arrow.range[1], tokens.after.range[0]]);
}
});
}
}
}
return {
ArrowFunctionExpression: spaces
};
}
};