Ensure "New Relation..." is always available (fixes #2066)

js/id/ui/raw_membership_editor.js

@@ -152,6 +152,7 @@ iD.ui.RawMembershipEditor = function(context) {
                     .attr('type', 'text')
                     .attr('class', 'member-entity-input')
                     .call(d3.combobox()
+                        .minItems(1)
                         .fetcher(function(value, callback) {
                             callback(relations(value));
                         })

js/lib/d3.combobox.js

@@ -1,7 +1,8 @@
 d3.combobox = function() {
     var event = d3.dispatch('accept'),
         data = [],
-        suggestions = [];
+        suggestions = [],
+        minItems = 2;
 
     var fetcher = function(val, cb) {
         cb(data.filter(function(d) {
@@ -192,7 +193,7 @@ d3.combobox = function() {
         }
 
         function render() {
-            if (suggestions.length > 1 && document.activeElement === input.node()) {
+            if (suggestions.length >= minItems && document.activeElement === input.node()) {
                 show();
             } else {
                 hide();
@@ -258,5 +259,11 @@ d3.combobox = function() {
         return combobox;
     };
 
+    combobox.minItems = function(_) {
+        if (!arguments.length) return minItems;
+        minItems = _;
+        return combobox;
+    };
+
     return d3.rebind(combobox, event, 'on');
 };

test/spec/lib/d3.combobox.js

@@ -95,6 +95,13 @@ describe("d3.combobox", function() {
         expect(body.selectAll('.combobox-option').size()).to.equal(0);
     });
 
+    it("shows menu on focus if it would contain at least minItems items", function() {
+        combobox.minItems(1);
+        input.property('value', 'f').call(combobox.data(data));
+        input.node().focus();
+        expect(body.selectAll('.combobox-option').size()).to.equal(1);
+    });
+
     it("shows all entries when clicking on the caret", function() {
         input.property('value', 'foo').call(combobox.data(data));
         happen.mousedown(body.selectAll('.combobox-caret').node());