From 5ea6c9a273405833b6c7911504da876cf5e10986 Mon Sep 17 00:00:00 2001
From: Matt Lauber <github@mklauber.com>
Date: Thu, 12 Apr 2018 08:21:49 -0400
Subject: [PATCH] Modify the is operator to allow multiple types to be
 specified. (#2982)

* Modify the is operator to allow multiple types to be specified.

* Fixed indentation.

* Fixed indentation.

* Rewritten to maintain input order when multiple filters provided.

* Updated documentation.

* Update is.tid
---
 core/modules/filters/is.js                    | 38 ++++++++++++++-----
 .../tw5.com/tiddlers/filters/examples/is.tid  |  1 +
 editions/tw5.com/tiddlers/filters/is.tid      |  6 ++-
 3 files changed, 34 insertions(+), 11 deletions(-)

diff --git a/core/modules/filters/is.js b/core/modules/filters/is.js
index 514443a62..99d86597f 100644
--- a/core/modules/filters/is.js
+++ b/core/modules/filters/is.js
@@ -26,16 +26,9 @@ function getIsFilterOperators() {
 Export our filter function
 */
 exports.is = function(source,operator,options) {
-	// Dispatch to the correct isfilteroperator
-	var isFilterOperators = getIsFilterOperators();
-	if(operator.operand) {
-		var isFilterOperator = isFilterOperators[operator.operand];
-		if(isFilterOperator) {
-			return isFilterOperator(source,operator.prefix,options);
-		} else {
-			return [$tw.language.getString("Error/IsFilterOperator")];
-		}
-	} else {
+
+
+	if( !operator.operand) {
 		// Return all tiddlers if the operand is missing
 		var results = [];
 		source(function(tiddler,title) {
@@ -43,6 +36,31 @@ exports.is = function(source,operator,options) {
 		});
 		return results;
 	}
+
+	// Get our isfilteroperators
+	var isFilterOperators = getIsFilterOperators(),
+	    subops = operator.operand.split("+"),
+		filteredResults = {},
+		results = [];
+	for (var t=0; t<subops.length; t++) {
+		var subop = isFilterOperators[subops[t]];
+		if(subop) {
+			filteredResults[subops[t]] = subop(source,operator.prefix,options);
+		} else {
+			return [$tw.language.getString("Error/IsFilterOperator")];
+		}
+		
+	}
+	
+    source(function(tiddler,title) {
+        for (var t=0; t<subops.length; t++) {
+            if (filteredResults[subops[t]].indexOf(title) != -1){
+                results.push(title);
+                break;
+            }
+        }
+    });
+	return results;
 };
 
 })();
diff --git a/editions/tw5.com/tiddlers/filters/examples/is.tid b/editions/tw5.com/tiddlers/filters/examples/is.tid
index d81a9bf77..29310bcbf 100644
--- a/editions/tw5.com/tiddlers/filters/examples/is.tid
+++ b/editions/tw5.com/tiddlers/filters/examples/is.tid
@@ -11,3 +11,4 @@ type: text/vnd.tiddlywiki
 <<.operator-example 5 "[all[shadows]is[system]tag[$:/tags/Stylesheet]]" "shadow system stylesheets">>
 <<.operator-example 6 "[is[shadow]]" "overridden shadow tiddlers">>
 <<.operator-example 7 "[is[missing]]" "empty because its input contains only tiddlers that exist">>
+<<.operator-example 8 "[all[tiddlers+shadows]is[tiddler+shadow]]" "contains the entire input list">>
diff --git a/editions/tw5.com/tiddlers/filters/is.tid b/editions/tw5.com/tiddlers/filters/is.tid
index fb7f6a26c..214661839 100644
--- a/editions/tw5.com/tiddlers/filters/is.tid
+++ b/editions/tw5.com/tiddlers/filters/is.tid
@@ -11,7 +11,11 @@ op-parameter-name: C
 op-output: those input tiddlers that belong to category <<.place C>>
 op-neg-output: those input tiddlers that do <<.em not>> belong to category <<.place C>>
 
-The parameter <<.place C>> is one of the following fundamental categories:
+The parameter <<.place C>> specifies zero or more fundamental categories using the following syntax:
+
+<$railroad text="""
+[{: ("current" | "missing" |: "orphans" | "shadows" | "tags" | "tiddlers" ) +"+" }]
+"""/>
 
 |!Category |!Matches any tiddler that... |
 |^`current` |is the [[current tiddler|Current Tiddler]] |