comma-style.js
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/**
* @fileoverview Comma style - enforces comma styles of two types: last and first
* @author Vignesh Anand aka vegetableman
* @copyright 2014 Vignesh Anand. All rights reserved.
* @copyright 2015 Evan Simmons. All rights reserved.
*/
"use strict";
var astUtils = require("../ast-utils");
//------------------------------------------------------------------------------
// Rule Definition
//------------------------------------------------------------------------------
module.exports = function(context) {
var style = context.options[0] || "last",
exceptions = {};
if (context.options.length === 2 && context.options[1].hasOwnProperty("exceptions")) {
exceptions = context.options[1].exceptions;
}
//--------------------------------------------------------------------------
// Helpers
//--------------------------------------------------------------------------
/**
* Determines if a given token is a comma operator.
* @param {ASTNode} token The token to check.
* @returns {boolean} True if the token is a comma, false if not.
* @private
*/
function isComma(token) {
return !!token && (token.type === "Punctuator") && (token.value === ",");
}
/**
* Validates the spacing around single items in lists.
* @param {Token} previousItemToken The last token from the previous item.
* @param {Token} commaToken The token representing the comma.
* @param {Token} currentItemToken The first token of the current item.
* @param {Token} reportItem The item to use when reporting an error.
* @returns {void}
* @private
*/
function validateCommaItemSpacing(previousItemToken, commaToken, currentItemToken, reportItem) {
// if single line
if (astUtils.isTokenOnSameLine(commaToken, currentItemToken) &&
astUtils.isTokenOnSameLine(previousItemToken, commaToken)) {
return;
} else if (!astUtils.isTokenOnSameLine(commaToken, currentItemToken) &&
!astUtils.isTokenOnSameLine(previousItemToken, commaToken)) {
// lone comma
context.report(reportItem, {
line: commaToken.loc.end.line,
column: commaToken.loc.start.column
}, "Bad line breaking before and after ','.");
} else if (style === "first" && !astUtils.isTokenOnSameLine(commaToken, currentItemToken)) {
context.report(reportItem, "',' should be placed first.");
} else if (style === "last" && astUtils.isTokenOnSameLine(commaToken, currentItemToken)) {
context.report(reportItem, {
line: commaToken.loc.end.line,
column: commaToken.loc.end.column
}, "',' should be placed last.");
}
}
/**
* Checks the comma placement with regards to a declaration/property/element
* @param {ASTNode} node The binary expression node to check
* @param {string} property The property of the node containing child nodes.
* @private
* @returns {void}
*/
function validateComma(node, property) {
var items = node[property],
arrayLiteral = (node.type === "ArrayExpression"),
previousItemToken;
if (items.length > 1 || arrayLiteral) {
// seed as opening [
previousItemToken = context.getFirstToken(node);
items.forEach(function(item) {
var commaToken = item ? context.getTokenBefore(item) : previousItemToken,
currentItemToken = item ? context.getFirstToken(item) : context.getTokenAfter(commaToken),
reportItem = item || currentItemToken;
/*
* This works by comparing three token locations:
* - previousItemToken is the last token of the previous item
* - commaToken is the location of the comma before the current item
* - currentItemToken is the first token of the current item
*
* These values get switched around if item is undefined.
* previousItemToken will refer to the last token not belonging
* to the current item, which could be a comma or an opening
* square bracket. currentItemToken could be a comma.
*
* All comparisons are done based on these tokens directly, so
* they are always valid regardless of an undefined item.
*/
if (isComma(commaToken)) {
validateCommaItemSpacing(previousItemToken, commaToken,
currentItemToken, reportItem);
}
previousItemToken = item ? context.getLastToken(item) : previousItemToken;
});
/*
* Special case for array literals that have empty last items, such
* as [ 1, 2, ]. These arrays only have two items show up in the
* AST, so we need to look at the token to verify that there's no
* dangling comma.
*/
if (arrayLiteral) {
var lastToken = context.getLastToken(node),
nextToLastToken = context.getTokenBefore(lastToken);
if (isComma(nextToLastToken)) {
validateCommaItemSpacing(
context.getTokenBefore(nextToLastToken),
nextToLastToken,
lastToken,
lastToken
);
}
}
}
}
//--------------------------------------------------------------------------
// Public
//--------------------------------------------------------------------------
var nodes = {};
if (!exceptions.VariableDeclaration) {
nodes.VariableDeclaration = function(node) {
validateComma(node, "declarations");
};
}
if (!exceptions.ObjectExpression) {
nodes.ObjectExpression = function(node) {
validateComma(node, "properties");
};
}
if (!exceptions.ArrayExpression) {
nodes.ArrayExpression = function(node) {
validateComma(node, "elements");
};
}
return nodes;
};
module.exports.schema = [
{
"enum": ["first", "last"]
},
{
"type": "object",
"properties": {
"exceptions": {
"type": "object",
"additionalProperties": {
"type": "boolean"
}
}
},
"additionalProperties": false
}
];