Introduce "field" suffix for "has" filter operator (#2066)

* has:field — tested & documented

allows to test whether a field exists

* fixed inverted condition

* added from version to docs

core/modules/filters/has.js

@@ -16,19 +16,37 @@ Filter operator for checking if a tiddler has the specified field
 Export our filter function
 */
 exports.has = function(source,operator,options) {
-	var results = [];
-	if(operator.prefix === "!") {
-		source(function(tiddler,title) {
-			if(!tiddler || (tiddler && (!$tw.utils.hop(tiddler.fields,operator.operand) || tiddler.fields[operator.operand] === ""))) {
-				results.push(title);
-			}
-		});
+	var results = [],
+		invert = operator.prefix === "!";
+
+	if(operator.suffix === "field") {
+		if(invert) {
+			source(function(tiddler,title) {
+				if(!tiddler || (tiddler && (!$tw.utils.hop(tiddler.fields,operator.operand)))) {
+					results.push(title);
+				}
+			});
+		} else {
+			source(function(tiddler,title) {
+				if(tiddler && $tw.utils.hop(tiddler.fields,operator.operand)) {
+					results.push(title);
+				}
+			});
+		}
 	} else {
-		source(function(tiddler,title) {
-			if(tiddler && $tw.utils.hop(tiddler.fields,operator.operand) && !(tiddler.fields[operator.operand] === "" || tiddler.fields[operator.operand].length === 0)) {
-				results.push(title);
-			}
-		});
+		if(invert) {
+			source(function(tiddler,title) {
+				if(!tiddler || !$tw.utils.hop(tiddler.fields,operator.operand) || (tiddler.fields[operator.operand] !== "")) {
+					results.push(title);
+				}
+			});
+		} else {
+			source(function(tiddler,title) {
+				if(tiddler && $tw.utils.hop(tiddler.fields,operator.operand) && !(tiddler.fields[operator.operand] === "" || tiddler.fields[operator.operand].length === 0)) {
+					results.push(title);
+				}
+			});
+		}
 	}
 	return results;
 };

editions/test/tiddlers/tests/test-filters.js

@@ -71,11 +71,13 @@ describe("Filter tests", function() {
 		title: "a fourth tiddler",
 		text: "The quality of mercy is not drained by [[Tiddler Three]]",
 		tags: [],
+		empty: "not",
 		modifier: "JohnDoe"});
 	wiki.addTiddler({
 		title: "one",
 		text: "This is the text of tiddler [[one]]",
 		list: "[[Tiddler Three]] [[TiddlerOne]]",
+		empty: "",
 		modifier: "JohnDoe"});
 
 	// Our tests
@@ -191,6 +193,12 @@ describe("Filter tests", function() {
 		expect(wiki.filterTiddlers("[!has[modified]sort[title]]").join(",")).toBe("a fourth tiddler,one");
 	});
 
+	it("should handle the has:field operator", function() {
+		expect(wiki.filterTiddlers("[has:field[empty]sort[title]]").join(",")).toBe("a fourth tiddler,one");
+		expect(wiki.filterTiddlers("[!has:field[empty]sort[title]]").join(",")).toBe("$:/TiddlerTwo,Tiddler Three,TiddlerOne");
+	});
+
+
 	it("should handle the limit operator", function() {
 		expect(wiki.filterTiddlers("[!is[system]sort[title]limit[2]]").join(",")).toBe("a fourth tiddler,one");
 		expect(wiki.filterTiddlers("[prefix[Tid]sort[title]limit[1]]").join(",")).toBe("Tiddler Three");

editions/tw5.com/tiddlers/filters/examples/has.tid

@@ -1,9 +1,11 @@
-created: 20150118165921000
-modified: 20150118183219000
+created: 20151111150157416
+emptyfield: 
+modified: 20151111150201093
 tags: [[has Operator]] [[Operator Examples]]
 title: has Operator (Examples)
 type: text/vnd.tiddlywiki
 
 <<.operator-example 1 "[has[color]]">>
 <<.operator-example 2 "[tag[Concepts]!has[modified]]">>
-
+<<.operator-example 3 "[has:field[emptyfield]]">>
+<<.operator-example 4 "[all[current]!has:field[doesntexist]]">>

editions/tw5.com/tiddlers/filters/has.tid

@@ -1,14 +1,16 @@
-created: 20140410103123179
-modified: 20150203191843000
-tags: [[Filter Operators]] [[Common Operators]] [[Field Operators]] [[Negatable Operators]]
-title: has Operator
-type: text/vnd.tiddlywiki
 caption: has
-op-purpose: filter the input by field existence
+created: 20140410103123179
+modified: 20151111150117431
 op-input: a [[selection of titles|Title Selection]]
+op-neg-output: ''without suffix'' or with ''suffix `value`''<br>&raquo; those input tiddlers in which field <<.place F>> does <<.em not>> exist or has an empty value<br>''suffix `field`''<br>&raquo; those input tiddlers in which field <<.place F>> exists
+op-output: ''without suffix'' or with ''suffix `value`''<br>&raquo; those input tiddlers in which field <<.place F>> has a non-empty value<br>''suffix `field`''<br>&raquo; those input tiddlers in which field <<.place F>> does <<.em not>> exist
 op-parameter: the name of a [[field|TiddlerFields]]
 op-parameter-name: F
-op-output: those input tiddlers in which field <<.place F>> has a non-empty value
-op-neg-output: those input tiddlers in which field <<.place F>> does <<.em not>> exist or has an empty value
+op-purpose: filter the input by field existence
+op-suffix: <<.from-version "5.1.14">> optionally, the name of a [[field|TiddlerFields]]
+op-suffix-name: F
+tags: [[Filter Operators]] [[Common Operators]] [[Field Operators]] [[Negatable Operators]]
+title: has Operator
+type: text/vnd.tiddlywiki
 
-<<.operator-examples "has">>
+<<.operator-examples "has">>