[main] catch startup errors

Cf. #401 (comments)

Author: pkra

lib/main.js

@@ -91,6 +91,7 @@ var document, window, content, html; // the DOM elements
 var queue = [];       // queue of typesetting requests of the form [data,callback]
 var data, callback, originalData;   // the current queue item
 var errors = [];      // errors collected durring the typesetting
+var sErrors = [];     // errors collected durring MathJax startup
 var ID = 0;           // id for this SVG element
 
 //
@@ -519,7 +520,10 @@ function ConfigureMathJax() {
         if (MathJax.OutputJax.SVG.resetGlyphs) MathJax.OutputJax.SVG.resetGlyphs(true);
         MathJax.ElementJax.mml.ID = 0;
         serverState = STATE.READY;
-        MathJax.Hub.Queue(StartQueue);
+        MathJax.Hub.Queue(
+            function () {sErrors = errors},
+            StartQueue
+          );
       });
     }
   };
@@ -730,7 +734,7 @@ function GetSVG(result) {
 //
 function StartQueue() {
   data = callback = originalData = null;       //  clear existing equation, if any
-  errors = [];                  //  clear any errors
+  errors = sErrors; sErrors = [];              //  clear any errors
   if (!queue.length) return;    //  return if nothing to do
 
   serverState = STATE.BUSY;

test/base-01-errors-startup.js

@@ -0,0 +1,28 @@
+var tape = require('tape');
+var mjAPI = require('../lib/main.js');
+
+// NOTE this test must first (in tape) to test the startup phase (hence the filename contains "01")
+
+tape('Catch errors during startup phase', function(t) {
+  t.plan(1);
+  mjAPI.config({
+    extensions: 'blargh'
+  });
+  mjAPI.typeset(
+    {
+      math: 'x',
+      format: 'TeX',
+      mml: true
+    },
+    function(data) {
+      t.ok(
+        data.errors,
+        'Error (loading non-existent extension) is caught in output'
+      );
+     // reset configuration
+     mjAPI.config({
+        extensions: 'tex2jax'
+      });
+    }
+  );
+});