Add option for trailing commas in objects

bin/jscodefmt

@@ -5,7 +5,7 @@ const minimist = require("minimist");
 const jscodefmt = require("../index");
 
 const argv = minimist(process.argv.slice(2), {
-  boolean: ["write", "useFlowParser", "bracket-spacing", "single-quote"]
+  boolean: ["write", "useFlowParser", "bracket-spacing", "single-quote", "trailing-comma"]
 });
 
 const filename = argv["_"][0];
@@ -16,7 +16,8 @@ const output = jscodefmt.format(fs.readFileSync(filename, "utf8"), {
   tabWidth: argv['tab-width'],
   bracketSpacing: argv['bracket-spacing'],
   useFlowParser: argv['flow-parser'],
-  singleQuote: argv["single-quote"]
+  singleQuote: argv["single-quote"],
+  trailingComma: argv["trailing-comma"]
 });
 
 if(write) {

src/pp.js

@@ -46,6 +46,10 @@ function conditionalGroup(states, opts) {
   }));
 }
 
+function ifBreak(contents) {
+  return { type: 'if-break', contents };
+}
+
 function iterDoc(topDoc, func) {
   const docs = [topDoc];
 
@@ -163,6 +167,11 @@ function fits(next, restCommands, width) {
         case "group":
           cmds.push([ind, doc.break ? MODE_BREAK : mode, doc.contents]);
           break;
+        case "if-break":
+          if(mode === MODE_BREAK) {
+            cmds.push([ind, mode, doc.contents]);
+          }
+          break;
         case "line":
           switch(mode) {
             case MODE_FLAT:
@@ -264,6 +273,11 @@ function print(w, doc) {
               break;
           }
           break;
+        case "if-break":
+          if(mode === MODE_BREAK) {
+            cmds.push([ind, MODE_BREAK, doc.contents]);
+          }
+          break;
         case "line":
           switch(mode) {
             case MODE_FLAT:
@@ -314,5 +328,5 @@ function print(w, doc) {
 module.exports = {
   fromString, concat, isEmpty, join,
   line, softline, hardline, literalline, group, multilineGroup,
-  conditionalGroup, hasHardLine, indent, print, getFirstString
+  conditionalGroup, ifBreak, hasHardLine, indent, print, getFirstString
 };

src/printer.js

@@ -16,6 +16,7 @@ var indent = pp.indent;
 var getFirstString = pp.getFirstString;
 var hasHardLine = pp.hasHardLine;
 var conditionalGroup = pp.conditionalGroup;
+var ifBreak = pp.ifBreak;
 var normalizeOptions = require("./options").normalize;
 var types = require("ast-types");
 var namedTypes = types.namedTypes;
@@ -629,6 +630,7 @@ function genericPrintNoParens(path, options, print) {
   case "ObjectTypeAnnotation":
     var allowBreak = false;
     var isTypeAnnotation = n.type === "ObjectTypeAnnotation";
+    var isObjectExpression = n.type === "ObjectExpression";
     // Leave this here because we *might* want to make this
     // configurable later -- flow accepts ";" for type separators
     var separator = (isTypeAnnotation ? "," : ",");
@@ -663,6 +665,7 @@ function genericPrintNoParens(path, options, print) {
           (options.bracketSpacing ? line : softline),
           join(concat([ separator, line ]), props)
         ])),
+        ifBreak((isObjectExpression && options.trailingComma) ? "," : ""),
         (options.bracketSpacing ? line : softline),
         rightBrace,
         path.call(print, "typeAnnotation")
@@ -1671,7 +1674,6 @@ function printMethod(path, options, print) {
 
 function printArgumentsList(path, options, print) {
   var printed = path.map(print, "arguments");
-  var trailingComma = util.isTrailingCommaEnabled(options, "parameters");
   var args;
 
   if (printed.length === 0) {