From 5dd3d97760083f7c6ba9a6cd6186525edb3fb836 Mon Sep 17 00:00:00 2001
From: Jermolene <jeremy@jermolene.com>
Date: Wed, 12 Jul 2017 16:59:56 +0100
Subject: [PATCH] Extend the set widget with tiddler, field and index
 attributes

---
 core/modules/widgets/setvariable.js           | 20 ++++++++++++---
 .../tw5.com/tiddlers/widgets/SetWidget.tid    | 25 +++++++++++++++++--
 2 files changed, 40 insertions(+), 5 deletions(-)

diff --git a/core/modules/widgets/setvariable.js b/core/modules/widgets/setvariable.js
index 76844b62d..3da727066 100755
--- a/core/modules/widgets/setvariable.js
+++ b/core/modules/widgets/setvariable.js
@@ -41,6 +41,9 @@ SetWidget.prototype.execute = function() {
 	this.setName = this.getAttribute("name","currentTiddler");
 	this.setFilter = this.getAttribute("filter");
 	this.setSelect = this.getAttribute("select");
+	this.setTiddler = this.getAttribute("tiddler");
+	this.setField = this.getAttribute("field");
+	this.setIndex = this.getAttribute("index");
 	this.setValue = this.getAttribute("value");
 	this.setEmptyValue = this.getAttribute("emptyValue");
 	// Set context variable
@@ -54,7 +57,18 @@ Get the value to be assigned
 */
 SetWidget.prototype.getValue = function() {
 	var value = this.setValue;
-	if(this.setFilter) {
+	if(this.setTiddler) {
+		var tiddler = this.wiki.getTiddler(this.setTiddler);
+		if(!tiddler) {
+			value = this.setEmptyValue;
+		} else if(this.setField) {
+			value = tiddler.getFieldString(this.setField) || this.setEmptyValue;
+		} else if(this.setIndex) {
+			value = this.wiki.extractTiddlerDataItem(this.setTiddler,this.setIndex,this.setEmptyValue);
+		} else {
+			value = tiddler.fields.text || this.setEmptyValue ;
+		}
+	} else if(this.setFilter) {
 		var results = this.wiki.filterTiddlers(this.setFilter,this);
 		if(!this.setValue) {
 			var select;
@@ -73,7 +87,7 @@ SetWidget.prototype.getValue = function() {
 	} else if(!value && this.setEmptyValue) {
 		value = this.setEmptyValue;
 	}
-	return value;
+	return value || "";
 };
 
 /*
@@ -81,7 +95,7 @@ Selectively refreshes the widget if needed. Returns true if the widget or any of
 */
 SetWidget.prototype.refresh = function(changedTiddlers) {
 	var changedAttributes = this.computeAttributes();
-	if(changedAttributes.name || changedAttributes.filter || changedAttributes.select ||changedAttributes.value || changedAttributes.emptyValue ||
+	if(changedAttributes.name || changedAttributes.filter || changedAttributes.select || changedAttributes.tiddler || (this.setTiddler && changedTiddlers[this.setTiddler]) || changedAttributes.field || changedAttributes.index || changedAttributes.value || changedAttributes.emptyValue ||
 	   (this.setFilter && this.getValue() != this.variables[this.setName].value)) {
 		this.refreshSelf();
 		return true;
diff --git a/editions/tw5.com/tiddlers/widgets/SetWidget.tid b/editions/tw5.com/tiddlers/widgets/SetWidget.tid
index bf1ec571f..214aab9cc 100644
--- a/editions/tw5.com/tiddlers/widgets/SetWidget.tid
+++ b/editions/tw5.com/tiddlers/widgets/SetWidget.tid
@@ -1,6 +1,6 @@
 caption: set
 created: 20131115182700000
-modified: 20161017122456014
+modified: 20170712153850528
 tags: Widgets
 title: SetWidget
 type: text/vnd.tiddlywiki
@@ -16,9 +16,12 @@ The content of the `<$set>` widget is the scope for the value assigned to the va
 |!Attribute |!Description |
 |name |The name of the variable to assign (defaults to "currentTiddler") |
 |value |The value to assign to the variable if the filter is missing or not empty |
+|tiddler |<<.from-version "5.1.15">> Optional title of the tiddler from which to read the value |
+|field |<<.from-version "5.1.15">> Optional field of the tiddler from which to read the value (only used if ''tiddler'' is used) |
+|index |<<.from-version "5.1.15">> Optional index of the tiddler from which to read the value (only used if ''tiddler'' is used) |
 |filter |An optional filter to be evaluated and assigned to the variable (see below) |
 |select |<<.from-version "5.1.14">> An optional zero-based index of the item to return from the filter output (see below) |
-|emptyValue |The value to assign to the variable if the filter is present and evaluates to an empty list (see below) |
+|emptyValue |The value to assign to the variable if the specified value is missing or empty (see below) |
 
 !! Simple Variable Assignment
 
@@ -67,3 +70,21 @@ This form of the set variable widget evaluates the filter and assigns the result
 <$text text=<<myVariable>>/>
 </$set>
 ```
+
+!! Transcluded Variable Assignment
+
+<<.from-version "5.1.15">> This form of the set variable widget obtains the value to assign to the variable from a value in a tiddler field or index. For example:
+
+```
+<$set name="myVariable" tiddler="HelloThere" field="text">
+<$text text=<<myVariable>>/>
+</$set>
+```
+
+The example above could also be written as `<$set name="myVariable" value={{HelloThere!!text}}>`. The advantage of using the ''tiddler'' attribute is that the tiddler title and field or index can themselves be computed. For example:
+
+```
+<$set name="myVariable" tiddler=<<myTiddler>> field={{$:/currentField}}>
+<$text text=<<myVariable>>/>
+</$set>
+```