Write flags out when serializing.

lib/po.js

@@ -193,6 +193,11 @@ PO.Item.prototype.toString = function () {
         });
     }
 
+    var flags = Object.keys(this.flags);
+    if (flags.length > 0) {
+        lines.push(util.format('#, %s', flags.join(",")));
+    }
+
     ['msgid', 'msgid_plural', 'msgstr'].forEach(function (keyword) {
         var text = that[keyword];
         if (text != null) {

test/write.js

@@ -0,0 +1,26 @@
+var assert = require('assert');
+var fs = require('fs');
+var PO = require('..');
+
+function assertHasLine(str, line) {
+    var lines = str.split("\n");
+    var found = false;
+
+    for (var i = 0; i < lines.length; i++) {
+        if (lines[i].trim() === line) {
+            found = true;
+            break;
+        }
+    }
+
+    assert(found, "Could not find line: " + line);
+}
+
+describe('Write', function () {
+    it('write flags', function () {
+        var input = fs.readFileSync(__dirname + '/fixtures/fuzzy.po', 'utf8');
+        var po = PO.parse(input);
+        var str = po.toString();
+        assertHasLine(str, "#, fuzzy");
+    });
+});