Fixes to split operator, plus instructions for using it to do search and replace

core/modules/filters/strings.js

@@ -39,13 +39,17 @@ exports.trim = makeStringBinaryOperator(
 );
 
 exports.split = makeStringBinaryOperator(
-	function(a,b) {return ("" + a).split(b).filter(function(str) {return !!str;});}
+	function(a,b) {return ("" + a).split(b);}
 );
 
 exports.join = makeStringReducingOperator(
 	function(accumulator,value,operand) {
-		return "" + (accumulator ? accumulator + (operand || "") + value : value);
-	}
+		if(accumulator === null) {
+			return value;
+		} else {
+			return accumulator + operand + value;
+		}
+	},null
 );
 
 function makeStringBinaryOperator(fnCalc) {
@@ -59,7 +63,6 @@ function makeStringBinaryOperator(fnCalc) {
 }
 
 function makeStringReducingOperator(fnCalc,initialValue) {
-	initialValue = initialValue || "";
 	return function(source,operator,options) {
 		var result = [];
 		source(function(tiddler,title) {
@@ -75,10 +78,15 @@ exports.splitregexp = function(source,operator,options) {
 	var result = [],
 		suffix = operator.suffix || "",
 		flags = (suffix.indexOf("m") !== -1 ? "m" : "") + (suffix.indexOf("i") !== -1 ? "i" : ""),
-		regExp = new RegExp(operator.operand || "",flags);
+		regExp;
+	try {
+		regExp = new RegExp(operator.operand || "",flags);		
+	} catch(ex) {
+		return ["RegExp error: " + ex];
+	}
 	source(function(tiddler,title) {
 		Array.prototype.push.apply(result,title.split(regExp));
-	});
+	});		
 	return result;
 };
 

editions/tw5.com/tiddlers/filters/split Operator.tid

@@ -12,4 +12,28 @@ type: text/vnd.tiddlywiki
 
 <<.from-version "5.1.20">>
 
+Note that in some circumstances the <<.op split>> operator will include blank items in the list of results. For example, 
+
+```
+[[the band thethe are the best the]split[the]]
+```
+
+The following results are returned:
+
+```
+["", " band ", "", " are ", " best ", ""]
+```
+
+Where it might be expected that the results would be:
+
+```
+[" band ", " are ", " best "]
+```
+
+The blank items mark the boundaries between matches. If they are not required they can be removed with the ''blank'' category of the [[is Operator]]: `[[the band thethe are the best the]split[the]!is[blank]]`.
+
+The reason that the blank items can be useful is that they allow search and replace operations to be constructed from a combination of the [[split Operator]] or [[splitregexp Operator]] and the [[join Operator]]. For example:
+
+<<.operator-example 1 "[[the band thethe are the best the]split[the]join[every]]">>
+
 <<.operator-examples "split">>

editions/tw5.com/tiddlers/filters/splitregexp Operator.tid

@@ -13,4 +13,32 @@ type: text/vnd.tiddlywiki
 
 <<.from-version "5.1.20">>
 
+Note that in some circumstances the <<.op splitregexp>> operator will include blank items in the list of results. For example, 
+
+```
+[[the band thethe are the best the]splitregexp[the]]
+```
+
+The following results are returned:
+
+```
+["", " band ", "", " are ", " best ", ""]
+```
+
+Where it might be expected that the results would be:
+
+```
+[" band ", " are ", " best "]
+```
+
+The blank items mark the boundaries between matches. If they are not required they can be removed with the ''blank'' category of the [[is Operator]]: `[[the band thethe are the best the]splitregexp[the]!is[blank]]`.
+
+The reason that the blank items can be useful is that they allow search and replace operations to be constructed from a combination of the [[split Operator]] or [[splitregexp Operator]] and the [[join Operator]]. For example:
+
+<<.operator-example 1 "[[nobody, really; wants; to see -- all this \punctuation]splitregexp[,|;|-|\\]join[...]]">>
+
+Syntax errors in the regular expression will cause the filter to return an error message. For example:
+
+<<.operator-example 2 "[[the cat sat on the mat]splitregexp[\]]">>
+
 <<.operator-examples "splitregexp">>