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 sourceCode = context.getSourceCode();
const baseConfig = typeof context.options[0] === "string" ? context.options[0] : "always";
const overrideConfig = typeof context.options[0] === "object" ? context.options[0] : {};
/**
* 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
)
);
}
/**
* Gets the config for a given function
* @param {ASTNode} node The function node
* @returns {string} "always", "never", or "ignore"
*/
function getConfigForFunction(node) {
if (node.type === "ArrowFunctionExpression") {
// Always ignore non-async functions and arrow functions without parens, e.g. async foo => bar
if (node.async && astUtils.isOpeningParenToken(sourceCode.getFirstToken(node, { skip: 1 }))) {
// For backwards compatibility, the base config does not apply to async arrow functions.
return overrideConfig.asyncArrow || "ignore";
}
} else if (isNamedFunction(node)) {
return overrideConfig.named || baseConfig;
// `generator-star-spacing` should warn anonymous generators. E.g. `function* () {}`
} else if (!node.generator) {
return overrideConfig.anonymous || baseConfig;
}
return "ignore";
}
/**
* Checks the parens of a function node
* @param {ASTNode} node A function node
* @returns {void}
*/
function checkFunction(node) {
const functionConfig = getConfigForFunction(node);
if (functionConfig === "ignore") {
return;
}
const rightToken = sourceCode.getFirstToken(node, astUtils.isOpeningParenToken);
const leftToken = sourceCode.getTokenBefore(rightToken);
const hasSpacing = sourceCode.isSpaceBetweenTokens(leftToken, rightToken);
if (hasSpacing && functionConfig === "never") {
context.report({
node,
loc: leftToken.loc.end,
message: "Unexpected space before function parentheses.",
fix: fixer => fixer.removeRange([leftToken.range[1], rightToken.range[0]])
});
} else if (!hasSpacing && functionConfig === "always") {
context.report({
node,
loc: leftToken.loc.end,
message: "Missing space before function parentheses.",
fix: fixer => fixer.insertTextAfter(leftToken, " ")
});
}
}
return {
ArrowFunctionExpression: checkFunction,
FunctionDeclaration: checkFunction,
FunctionExpression: checkFunction
};
}
};