space-before-function-paren.js
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/**
* @fileoverview Rule to validate spacing before function paren.
* @author Mathias Schreck <https://github.com/lo1tuma>
*/
"use strict";
//------------------------------------------------------------------------------
// Requirements
//------------------------------------------------------------------------------
const astUtils = require("../ast-utils");
//------------------------------------------------------------------------------
// Rule Definition
//------------------------------------------------------------------------------
module.exports = {
meta: {
docs: {
description: "enforce consistent spacing before `function` definition opening parenthesis",
category: "Stylistic Issues",
recommended: false
},
fixable: "whitespace",
schema: [
{
oneOf: [
{
enum: ["always", "never"]
},
{
type: "object",
properties: {
anonymous: {
enum: ["always", "never", "ignore"]
},
named: {
enum: ["always", "never", "ignore"]
},
asyncArrow: {
enum: ["always", "never", "ignore"]
}
},
additionalProperties: false
}
]
}
]
},
create(context) {
const configuration = context.options[0],
sourceCode = context.getSourceCode();
let requireAnonymousFunctionSpacing = true,
forbidAnonymousFunctionSpacing = false,
requireNamedFunctionSpacing = true,
forbidNamedFunctionSpacing = false,
requireArrowFunctionSpacing = false,
forbidArrowFunctionSpacing = false;
if (typeof configuration === "object") {
requireAnonymousFunctionSpacing = (
!configuration.anonymous || configuration.anonymous === "always");
forbidAnonymousFunctionSpacing = configuration.anonymous === "never";
requireNamedFunctionSpacing = (
!configuration.named || configuration.named === "always");
forbidNamedFunctionSpacing = configuration.named === "never";
requireArrowFunctionSpacing = configuration.asyncArrow === "always";
forbidArrowFunctionSpacing = configuration.asyncArrow === "never";
} else if (configuration === "never") {
requireAnonymousFunctionSpacing = false;
forbidAnonymousFunctionSpacing = true;
requireNamedFunctionSpacing = false;
forbidNamedFunctionSpacing = true;
}
/**
* Determines whether a function has a name.
* @param {ASTNode} node The function node.
* @returns {boolean} Whether the function has a name.
*/
function isNamedFunction(node) {
if (node.id) {
return true;
}
const parent = node.parent;
return parent.type === "MethodDefinition" ||
(parent.type === "Property" &&
(
parent.kind === "get" ||
parent.kind === "set" ||
parent.method
)
);
}
/**
* Validates the spacing before function parentheses.
* @param {ASTNode} node The node to be validated.
* @returns {void}
*/
function validateSpacingBeforeParentheses(node) {
const isArrow = node.type === "ArrowFunctionExpression";
const isNamed = !isArrow && isNamedFunction(node);
const isAnonymousGenerator = node.generator && !isNamed;
const isNormalArrow = isArrow && !node.async;
const isArrowWithoutParens = isArrow && sourceCode.getFirstToken(node, 1).value !== "(";
let forbidSpacing, requireSpacing;
// isAnonymousGenerator → `generator-star-spacing` should warn it. E.g. `function* () {}`
// isNormalArrow → ignore always.
// isArrowWithoutParens → ignore always. E.g. `async a => a`
if (isAnonymousGenerator || isNormalArrow || isArrowWithoutParens) {
return;
}
if (isArrow) {
forbidSpacing = forbidArrowFunctionSpacing;
requireSpacing = requireArrowFunctionSpacing;
} else if (isNamed) {
forbidSpacing = forbidNamedFunctionSpacing;
requireSpacing = requireNamedFunctionSpacing;
} else {
forbidSpacing = forbidAnonymousFunctionSpacing;
requireSpacing = requireAnonymousFunctionSpacing;
}
const rightToken = sourceCode.getFirstToken(node, astUtils.isOpeningParenToken);
const leftToken = sourceCode.getTokenBefore(rightToken);
const location = leftToken.loc.end;
if (sourceCode.isSpaceBetweenTokens(leftToken, rightToken)) {
if (forbidSpacing) {
context.report({
node,
loc: location,
message: "Unexpected space before function parentheses.",
fix(fixer) {
return fixer.removeRange([leftToken.range[1], rightToken.range[0]]);
}
});
}
} else {
if (requireSpacing) {
context.report({
node,
loc: location,
message: "Missing space before function parentheses.",
fix(fixer) {
return fixer.insertTextAfter(leftToken, " ");
}
});
}
}
}
return {
FunctionDeclaration: validateSpacingBeforeParentheses,
FunctionExpression: validateSpacingBeforeParentheses,
ArrowFunctionExpression: validateSpacingBeforeParentheses
};
}
};