eslint/lib/rules/comma-style.js

   1 /**
   2  * @fileoverview Comma style - enforces comma styles of two types: last and first
   3  * @author Vignesh Anand aka vegetableman
   4  */
   5
   6 "use strict";
   7
   8 const astUtils = require("./utils/ast-utils");
   9
  10 //------------------------------------------------------------------------------
  11 // Rule Definition
  12 //------------------------------------------------------------------------------
  13
  14 module.exports = {
  15     meta: {
  16         type: "layout",
  17
  18         docs: {
  19             description: "enforce consistent comma style",
  20             category: "Stylistic Issues",
  21             recommended: false,
  22             url: "https://eslint.org/docs/rules/comma-style"
  23         },
  24
  25         fixable: "code",
  26
  27         schema: [
  28             {
  29                 enum: ["first", "last"]
  30             },
  31             {
  32                 type: "object",
  33                 properties: {
  34                     exceptions: {
  35                         type: "object",
  36                         additionalProperties: {
  37                             type: "boolean"
  38                         }
  39                     }
  40                 },
  41                 additionalProperties: false
  42             }
  43         ],
  44
  45         messages: {
  46             unexpectedLineBeforeAndAfterComma: "Bad line breaking before and after ','.",
  47             expectedCommaFirst: "',' should be placed first.",
  48             expectedCommaLast: "',' should be placed last."
  49         }
  50     },
  51
  52     create(context) {
  53         const style = context.options[0] || "last",
  54             sourceCode = context.getSourceCode();
  55         const exceptions = {
  56             ArrayPattern: true,
  57             ArrowFunctionExpression: true,
  58             CallExpression: true,
  59             FunctionDeclaration: true,
  60             FunctionExpression: true,
  61             ImportDeclaration: true,
  62             ObjectPattern: true,
  63             NewExpression: true
  64         };
  65
  66         if (context.options.length === 2 && Object.prototype.hasOwnProperty.call(context.options[1], "exceptions")) {
  67             const keys = Object.keys(context.options[1].exceptions);
  68
  69             for (let i = 0; i < keys.length; i++) {
  70                 exceptions[keys[i]] = context.options[1].exceptions[keys[i]];
  71             }
  72         }
  73
  74         //--------------------------------------------------------------------------
  75         // Helpers
  76         //--------------------------------------------------------------------------
  77
  78         /**
  79          * Modified text based on the style
  80          * @param {string} styleType Style type
  81          * @param {string} text Source code text
  82          * @returns {string} modified text
  83          * @private
  84          */
  85         function getReplacedText(styleType, text) {
  86             switch (styleType) {
  87                 case "between":
  88                     return `,${text.replace(astUtils.LINEBREAK_MATCHER, "")}`;
  89
  90                 case "first":
  91                     return `${text},`;
  92
  93                 case "last":
  94                     return `,${text}`;
  95
  96                 default:
  97                     return "";
  98             }
  99         }
 100
 101         /**
 102          * Determines the fixer function for a given style.
 103          * @param {string} styleType comma style
 104          * @param {ASTNode} previousItemToken The token to check.
 105          * @param {ASTNode} commaToken The token to check.
 106          * @param {ASTNode} currentItemToken The token to check.
 107          * @returns {Function} Fixer function
 108          * @private
 109          */
 110         function getFixerFunction(styleType, previousItemToken, commaToken, currentItemToken) {
 111             const text =
 112                 sourceCode.text.slice(previousItemToken.range[1], commaToken.range[0]) +
 113                 sourceCode.text.slice(commaToken.range[1], currentItemToken.range[0]);
 114             const range = [previousItemToken.range[1], currentItemToken.range[0]];
 115
 116             return function(fixer) {
 117                 return fixer.replaceTextRange(range, getReplacedText(styleType, text));
 118             };
 119         }
 120
 121         /**
 122          * Validates the spacing around single items in lists.
 123          * @param {Token} previousItemToken The last token from the previous item.
 124          * @param {Token} commaToken The token representing the comma.
 125          * @param {Token} currentItemToken The first token of the current item.
 126          * @param {Token} reportItem The item to use when reporting an error.
 127          * @returns {void}
 128          * @private
 129          */
 130         function validateCommaItemSpacing(previousItemToken, commaToken, currentItemToken, reportItem) {
 131
 132             // if single line
 133             if (astUtils.isTokenOnSameLine(commaToken, currentItemToken) &&
 134                     astUtils.isTokenOnSameLine(previousItemToken, commaToken)) {
 135
 136                 // do nothing.
 137
 138             } else if (!astUtils.isTokenOnSameLine(commaToken, currentItemToken) &&
 139                     !astUtils.isTokenOnSameLine(previousItemToken, commaToken)) {
 140
 141                 const comment = sourceCode.getCommentsAfter(commaToken)[0];
 142                 const styleType = comment && comment.type === "Block" && astUtils.isTokenOnSameLine(commaToken, comment)
 143                     ? style
 144                     : "between";
 145
 146                 // lone comma
 147                 context.report({
 148                     node: reportItem,
 149                     loc: {
 150                         line: commaToken.loc.end.line,
 151                         column: commaToken.loc.start.column
 152                     },
 153                     messageId: "unexpectedLineBeforeAndAfterComma",
 154                     fix: getFixerFunction(styleType, previousItemToken, commaToken, currentItemToken)
 155                 });
 156
 157             } else if (style === "first" && !astUtils.isTokenOnSameLine(commaToken, currentItemToken)) {
 158
 159                 context.report({
 160                     node: reportItem,
 161                     messageId: "expectedCommaFirst",
 162                     fix: getFixerFunction(style, previousItemToken, commaToken, currentItemToken)
 163                 });
 164
 165             } else if (style === "last" && astUtils.isTokenOnSameLine(commaToken, currentItemToken)) {
 166
 167                 context.report({
 168                     node: reportItem,
 169                     loc: {
 170                         line: commaToken.loc.end.line,
 171                         column: commaToken.loc.end.column
 172                     },
 173                     messageId: "expectedCommaLast",
 174                     fix: getFixerFunction(style, previousItemToken, commaToken, currentItemToken)
 175                 });
 176             }
 177         }
 178
 179         /**
 180          * Checks the comma placement with regards to a declaration/property/element
 181          * @param {ASTNode} node The binary expression node to check
 182          * @param {string} property The property of the node containing child nodes.
 183          * @private
 184          * @returns {void}
 185          */
 186         function validateComma(node, property) {
 187             const items = node[property],
 188                 arrayLiteral = (node.type === "ArrayExpression" || node.type === "ArrayPattern");
 189
 190             if (items.length > 1 || arrayLiteral) {
 191
 192                 // seed as opening [
 193                 let previousItemToken = sourceCode.getFirstToken(node);
 194
 195                 items.forEach(item => {
 196                     const commaToken = item ? sourceCode.getTokenBefore(item) : previousItemToken,
 197                         currentItemToken = item ? sourceCode.getFirstToken(item) : sourceCode.getTokenAfter(commaToken),
 198                         reportItem = item || currentItemToken;
 199
 200                     /*
 201                      * This works by comparing three token locations:
 202                      * - previousItemToken is the last token of the previous item
 203                      * - commaToken is the location of the comma before the current item
 204                      * - currentItemToken is the first token of the current item
 205                      *
 206                      * These values get switched around if item is undefined.
 207                      * previousItemToken will refer to the last token not belonging
 208                      * to the current item, which could be a comma or an opening
 209                      * square bracket. currentItemToken could be a comma.
 210                      *
 211                      * All comparisons are done based on these tokens directly, so
 212                      * they are always valid regardless of an undefined item.
 213                      */
 214                     if (astUtils.isCommaToken(commaToken)) {
 215                         validateCommaItemSpacing(previousItemToken, commaToken,
 216                             currentItemToken, reportItem);
 217                     }
 218
 219                     if (item) {
 220                         const tokenAfterItem = sourceCode.getTokenAfter(item, astUtils.isNotClosingParenToken);
 221
 222                         previousItemToken = tokenAfterItem
 223                             ? sourceCode.getTokenBefore(tokenAfterItem)
 224                             : sourceCode.ast.tokens[sourceCode.ast.tokens.length - 1];
 225                     }
 226                 });
 227
 228                 /*
 229                  * Special case for array literals that have empty last items, such
 230                  * as [ 1, 2, ]. These arrays only have two items show up in the
 231                  * AST, so we need to look at the token to verify that there's no
 232                  * dangling comma.
 233                  */
 234                 if (arrayLiteral) {
 235
 236                     const lastToken = sourceCode.getLastToken(node),
 237                         nextToLastToken = sourceCode.getTokenBefore(lastToken);
 238
 239                     if (astUtils.isCommaToken(nextToLastToken)) {
 240                         validateCommaItemSpacing(
 241                             sourceCode.getTokenBefore(nextToLastToken),
 242                             nextToLastToken,
 243                             lastToken,
 244                             lastToken
 245                         );
 246                     }
 247                 }
 248             }
 249         }
 250
 251         //--------------------------------------------------------------------------
 252         // Public
 253         //--------------------------------------------------------------------------
 254
 255         const nodes = {};
 256
 257         if (!exceptions.VariableDeclaration) {
 258             nodes.VariableDeclaration = function(node) {
 259                 validateComma(node, "declarations");
 260             };
 261         }
 262         if (!exceptions.ObjectExpression) {
 263             nodes.ObjectExpression = function(node) {
 264                 validateComma(node, "properties");
 265             };
 266         }
 267         if (!exceptions.ObjectPattern) {
 268             nodes.ObjectPattern = function(node) {
 269                 validateComma(node, "properties");
 270             };
 271         }
 272         if (!exceptions.ArrayExpression) {
 273             nodes.ArrayExpression = function(node) {
 274                 validateComma(node, "elements");
 275             };
 276         }
 277         if (!exceptions.ArrayPattern) {
 278             nodes.ArrayPattern = function(node) {
 279                 validateComma(node, "elements");
 280             };
 281         }
 282         if (!exceptions.FunctionDeclaration) {
 283             nodes.FunctionDeclaration = function(node) {
 284                 validateComma(node, "params");
 285             };
 286         }
 287         if (!exceptions.FunctionExpression) {
 288             nodes.FunctionExpression = function(node) {
 289                 validateComma(node, "params");
 290             };
 291         }
 292         if (!exceptions.ArrowFunctionExpression) {
 293             nodes.ArrowFunctionExpression = function(node) {
 294                 validateComma(node, "params");
 295             };
 296         }
 297         if (!exceptions.CallExpression) {
 298             nodes.CallExpression = function(node) {
 299                 validateComma(node, "arguments");
 300             };
 301         }
 302         if (!exceptions.ImportDeclaration) {
 303             nodes.ImportDeclaration = function(node) {
 304                 validateComma(node, "specifiers");
 305             };
 306         }
 307         if (!exceptions.NewExpression) {
 308             nodes.NewExpression = function(node) {
 309                 validateComma(node, "arguments");
 310             };
 311         }
 312
 313         return nodes;
 314     }
 315 };