[main] improve passing of input data to output

lib/main.js

@@ -85,7 +85,7 @@ var timer;                           // used to reset MathJax if it runs too lon
 var document, window, content, html; // the DOM elements
 
 var queue = [];       // queue of typesetting requests of the form [data,callback]
-var data, callback;   // the current queue item
+var data, callback, originalData;   // the current queue item
 var errors = [];      // errors collected durring the typesetting
 var ID = 0;           // id for this SVG element
 
@@ -648,7 +648,7 @@ function GetSVG(result) {
 //  Start typesetting the queued expressions
 //
 function StartQueue() {
-  data = callback = null;       //  clear existing equation, if any
+  data = callback = originalData = null;       //  clear existing equation, if any
   errors = [];                  //  clear any errors
   if (!queue.length) return;    //  return if nothing to do
 
@@ -660,7 +660,7 @@ function StartQueue() {
   // and set the content with the proper script type
   //
   var item = queue.shift();
-  data = item[0]; callback = item[1];
+  data = item[0]; callback = item[1]; originalData = item[2];
   content.innerHTML = "";
   MathJax.HTML.addElement(content,"script",{type: "math/"+TYPES[data.format]},[data.math]);
   html.setAttribute("xmlns:"+data.xmlns,"http://www.w3.org/1998/Math/MathML");
@@ -775,7 +775,7 @@ function ReturnResult(result) {
     state.ID = ID;
   }
   serverState = STATE.READY;
-  callback(result, data);
+  callback(result, originalData);
   if (serverState === STATE.READY) StartQueue();
 }
 
@@ -836,7 +836,7 @@ exports.typeset = function (data,callback) {
   }}
   if (data.state) {options.state = data.state}
   if (!TYPES[options.format]) {ReportError("Unknown format: "+options.format,callback); return}
-  queue.push([options,callback]);
+  queue.push([options,callback,Object.assign({},data)]);
   if (serverState == STATE.STOPPED) {RestartMathJax()}
   if (serverState == STATE.READY) StartQueue();
 }

test/pass_data.js

@@ -0,0 +1,16 @@
+var tape = require('tape');
+var mjAPI = require("../lib/main.js");
+
+tape('Passing data along', function(t) {
+    t.plan(1);
+    mjAPI.start();
+    var tex = 'x';
+    mjAPI.typeset({
+        math: tex,
+        format: "TeX",
+        css: true,
+        something: 'expected',
+    }, function(data, input) {
+        t.equal(input.something, 'expected', 'Data was passed along to output');
+    });
+});