From 611adadaed9e09adfc5e00dd0e51e851135227d0 Mon Sep 17 00:00:00 2001
From: Jeremy Ruston <jeremy@jermolene.com>
Date: Wed, 12 Feb 2025 10:04:46 +0000
Subject: [PATCH] Add apply filter run prefix

The map filter run prefix is often used as a way to move a computed value in the input list into a variable so that it can be used as a parameter of a filter operator. The apply filter run prefix extends this idea to make the input list available as variables $1, $2 etc. Unlike the map prefix, the apply filter run is only evaluated once.
---
 core/modules/filterrunprefixes/apply.js       | 29 +++++++++++++++++++
 .../data/filters/FilterRunPrefixesApply.tid   | 13 +++++++++
 2 files changed, 42 insertions(+)
 create mode 100644 core/modules/filterrunprefixes/apply.js
 create mode 100644 editions/test/tiddlers/tests/data/filters/FilterRunPrefixesApply.tid

diff --git a/core/modules/filterrunprefixes/apply.js b/core/modules/filterrunprefixes/apply.js
new file mode 100644
index 000000000..7673e7729
--- /dev/null
+++ b/core/modules/filterrunprefixes/apply.js
@@ -0,0 +1,29 @@
+/*\
+title: $:/core/modules/filterrunprefixes/apply.js
+type: application/javascript
+module-type: filterrunprefix
+
+
+
+\*/
+(function(){
+
+/*jslint node: true, browser: true */
+/*global $tw: false */
+"use strict";
+
+exports.apply = function(operationSubFunction) {
+	return function(results,source,widget) {
+		source = widget.wiki.makeTiddlerIterator([]);
+		var variables = {},
+			counter = 1;
+		results.each(function(title) {
+			variables["$" + counter] = title;
+			counter++;
+		});
+		results.clear();
+		results.pushTop(operationSubFunction(source,widget.makeFakeWidgetWithVariables(variables)));
+	};
+};
+
+})();
diff --git a/editions/test/tiddlers/tests/data/filters/FilterRunPrefixesApply.tid b/editions/test/tiddlers/tests/data/filters/FilterRunPrefixesApply.tid
new file mode 100644
index 000000000..5ed5a728e
--- /dev/null
+++ b/editions/test/tiddlers/tests/data/filters/FilterRunPrefixesApply.tid
@@ -0,0 +1,13 @@
+title: Filters/FilterRunPrefixes/Applu
+description: Applu filter run prefix
+type: text/vnd.tiddlywiki-multiple
+tags: [[$:/tags/wiki-test-spec]]
+
+title: Output
+
+\whitespace trim
+<$text text={{{ a b c :apply[<$1>addsuffix<$2>addsuffix<$3>] }}}/>
++
+title: ExpectedResult
+
+<p>abc</p>
\ No newline at end of file