From c65d08240b1f69078c8b3129cb9b00df56ada1d3 Mon Sep 17 00:00:00 2001
From: Jermolene <jeremy@jermolene.com>
Date: Mon, 28 Nov 2016 13:42:30 +0000
Subject: [PATCH] Add strict mode to tag operator

---
 core/modules/filters/tag.js               | 31 +++++++++++++++--------
 editions/tw5.com/tiddlers/filters/tag.tid | 23 ++++++++++-------
 2 files changed, 35 insertions(+), 19 deletions(-)

diff --git a/core/modules/filters/tag.js b/core/modules/filters/tag.js
index 408d7f98f..a421c61d7 100644
--- a/core/modules/filters/tag.js
+++ b/core/modules/filters/tag.js
@@ -17,19 +17,30 @@ Export our filter function
 */
 exports.tag = function(source,operator,options) {
 	var results = [];
-	if(operator.prefix === "!") {
+	if((operator.suffix || "").toLowerCase() === "strict" && !operator.operand) {
+		// New semantics:
+		// Always return copy of input if operator.operand is missing
 		source(function(tiddler,title) {
-			if(tiddler && !tiddler.hasTag(operator.operand)) {
-				results.push(title);
-			}
+			results.push(title);
 		});
 	} else {
-		source(function(tiddler,title) {
-			if(tiddler && tiddler.hasTag(operator.operand)) {
-				results.push(title);
-			}
-		});
-		results = options.wiki.sortByList(results,operator.operand);
+		// Old semantics:
+		if(operator.prefix === "!") {
+			// Returns a copy of the input if operator.operand is missing
+			source(function(tiddler,title) {
+				if(tiddler && !tiddler.hasTag(operator.operand)) {
+					results.push(title);
+				}
+			});
+		} else {
+			// Returns empty results if operator.operand is missing
+			source(function(tiddler,title) {
+				if(tiddler && tiddler.hasTag(operator.operand)) {
+					results.push(title);
+				}
+			});
+			results = options.wiki.sortByList(results,operator.operand);
+		}		
 	}
 	return results;
 };
diff --git a/editions/tw5.com/tiddlers/filters/tag.tid b/editions/tw5.com/tiddlers/filters/tag.tid
index 995cae7b1..929464b15 100644
--- a/editions/tw5.com/tiddlers/filters/tag.tid
+++ b/editions/tw5.com/tiddlers/filters/tag.tid
@@ -1,18 +1,23 @@
+caption: tag
 created: 20140410103123179
-modified: 20150203191853000
+modified: 20161126122900712
+op-input: a [[selection of titles|Title Selection]]
+op-neg-output: those input tiddlers that do <<.em not>> have tag <<.place T>>
+op-output: those input tiddlers that have tag <<.place T>>
+op-parameter: the title of a [[tag|Tagging]]
+op-parameter-name: T
+op-purpose: filter the input by tag
+op-suffix: <<.from-version "5.1.14">> optional `strict` flag
+op-suffix-name: S
 tags: [[Filter Operators]] [[Common Operators]] [[Tag Operators]] [[Negatable Operators]]
 title: tag Operator
 type: text/vnd.tiddlywiki
-caption: tag
-op-purpose: filter the input by tag
-op-input: a [[selection of titles|Title Selection]]
-op-parameter: the title of a [[tag|Tagging]]
-op-parameter-name: T
-op-output: those input tiddlers that have tag <<.place T>>
-op-neg-output: those input tiddlers that do <<.em not>> have tag <<.place T>>
 
 The output is [[sorted|Order of Tagged Tiddlers]] using the tag's <<.field list>> field and the tiddlers' <<.field list-before>> and <<.field list-after>> fields.
 
-If <<.place T>> is empty, the output of `tag` is empty, and the output of `!tag` is a copy of the input.
+The behaviour when <<.place T>> is empty depends on the settings of the <<.place S>> optional suffix:
+
+* if <<.place T>> is missing and  <<.place S>> is either missing or set to "loose", then the output of `tag` is empty, and the output of `!tag` is a copy of the input.
+* <<.from-version "5.1.14">> if <<.place T>> is missing and <<.place S>> is set to "strict", then the output of both `tag` and `!tag` is a copy of the input
 
 <<.operator-examples "tag">>