Prep for reporting location of template compilation errors.

Step 3: unroll main substitution into an explicit loop in
which we can track where each subst. occurs. With this and
the line-break index we build up front, we'll be able to
determine the source line and start/end line inded for
each replaced tag, and can then report that information
when a compilation failure (i.e. bad template syntax) is
detected.

lib/jqtpl.js

@@ -192,16 +192,36 @@ function unescape(args) {
  * @export
  */
 function buildTmplFn(markup) {
+    var source = '', breaks = [], tagexp, breakexp, matched, replace, start, finish;
+    tagexp = /\{\{(\/?)(\w+|.)(?:\(((?:[^\}]|\}(?!\}))*?)?\))?(?:\s+(.*?)?)?(\(((?:[^\}]|\}(?!\}))*?)\))?\s*\}\}/g;
+    breakexp = /(?:\r?\n)/g;
+
+    // Build index of line-break indexes for source error reporting
+    breaks = [0];
+    while ((matched = breakexp.exec(markup)) != null) {
+        breaks.push(matched.index + matched[0].length);
+    }
+
     // Convert the template into pure JavaScript
     markup = markup
         .trim()
         .replace(/([\\"])/g, '\\$1')
         .replace(/\n/g, '\\n')
         .replace(/\r/g, '\\r')
         .replace(/\$\{([^\}]*)\}/g, '{{= $1}}');
-    markup = markup
-        .replace(/\{\{(\/?)(\w+|.)(?:\(((?:[^\}]|\}(?!\}))*?)?\))?(?:\s+(.*?)?)?(\(((?:[^\}]|\}(?!\}))*?)\))?\s*\}\}/g,
-            function(all, slash, type, fnargs, target, parens, args) {
+
+    finish = 0;
+    while ((matched = tagexp.exec(markup)) != null) {
+        replace = tagsubst.apply(this, matched);
+
+        start = matched.index;
+        source += markup.slice(finish, start);
+        finish = start + matched[0].length;
+        source += replace;
+    }
+    source += markup.slice(finish);
+
+            function tagsubst(all, slash, type, fnargs, target, parens, args) {
                 var tag = exports.tag[type], def, expr, exprAutoFnDetect;
 
                 if (!tag) {
@@ -234,17 +254,16 @@ function buildTmplFn(markup) {
                         .split('$2').join(fnargs || def.$2 || '') +
                     '_.push("';
             }
-        );
 
     var source = (
         'var call,_=[],$data=$item.data;' +
         // Introduce the data as local variables using with(){}
         'with($data){_.push("\\n' + 
-            markup +
+            source +
         '");}' +
         'return _.join("");'
     );
-    
+
     return new Function('$', '$item', source);
 }