Fix greedy-flag bug

This bug occurs in the relatively rare case of a pattern matching the
empty string. It was reported in issue #1039. If for example a HTML
page contains an empty script tag `<script></script>` then the script
pattern will match anything inside, which is the empty string.

This empty string is then passed to the constructor of the Token class.
Since `""` is falsy in Javascript the property `matchedStr` is set to
`null`.

But the property `matchedStr` is needed to calculate the current
position for the greedy feature. A `null` value in `matchedStr` results
in a `pos` that is `NaN`. This causes the bug described in issue #1039.

Since the property `matchedStr` is only ever needed to calculate the
length of the Token, it is more efficient to store the length directly
instead of the string. As a side effect this also fixes issue #1039.

components/prism-core.js

@@ -289,7 +289,7 @@ var _ = _self.Prism = {
 				pattern = pattern.pattern || pattern;
 
 				// Don’t cache length as it changes during the loop
-				for (var i=0, pos = 0; i<strarr.length; pos += (strarr[i].matchedStr || strarr[i]).length, ++i) {
+				for (var i=0, pos = 0; i<strarr.length; pos += strarr[i].length, ++i) {
 
 					var str = strarr[i];
 
@@ -321,7 +321,7 @@ var _ = _self.Prism = {
 						    p = pos;
 
 						for (var len = strarr.length; k < len && p < to; ++k) {
-							p += (strarr[k].matchedStr || strarr[k]).length;
+							p += strarr[k].length;
 							// Move the index i to the element in strarr that is closest to from
 							if (from >= p) {
 								++i;
@@ -409,7 +409,7 @@ var Token = _.Token = function(type, content, alias, matchedStr, greedy) {
 	this.content = content;
 	this.alias = alias;
 	// Copy of the full string this token was created from
-	this.matchedStr = matchedStr || null;
+	this.length = (matchedStr || "").length|0;
 	this.greedy = !!greedy;
 };
 

prism.js

@@ -294,7 +294,7 @@ var _ = _self.Prism = {
 				pattern = pattern.pattern || pattern;
 
 				// Don’t cache length as it changes during the loop
-				for (var i=0, pos = 0; i<strarr.length; pos += (strarr[i].matchedStr || strarr[i]).length, ++i) {
+				for (var i=0, pos = 0; i<strarr.length; pos += strarr[i].length, ++i) {
 
 					var str = strarr[i];
 
@@ -326,7 +326,7 @@ var _ = _self.Prism = {
 						    p = pos;
 
 						for (var len = strarr.length; k < len && p < to; ++k) {
-							p += (strarr[k].matchedStr || strarr[k]).length;
+							p += strarr[k].length;
 							// Move the index i to the element in strarr that is closest to from
 							if (from >= p) {
 								++i;
@@ -414,7 +414,7 @@ var Token = _.Token = function(type, content, alias, matchedStr, greedy) {
 	this.content = content;
 	this.alias = alias;
 	// Copy of the full string this token was created from
-	this.matchedStr = matchedStr || null;
+	this.length = (matchedStr || "").length|0;
 	this.greedy = !!greedy;
 };