Add logic for new customized facets

main/src/com/google/refine/grel/ControlFunctionRegistry.java

@@ -141,6 +141,7 @@ import com.google.refine.grel.controls.ForRange;
 import com.google.refine.grel.controls.If;
 import com.google.refine.grel.controls.IsBlank;
 import com.google.refine.grel.controls.IsError;
+import com.google.refine.grel.controls.IsEmptyString;
 import com.google.refine.grel.controls.IsNonBlank;
 import com.google.refine.grel.controls.IsNotNull;
 import com.google.refine.grel.controls.IsNull;
@@ -305,6 +306,7 @@ public class ControlFunctionRegistry {
 
         registerControl("isNull", new IsNull());
         registerControl("isNotNull", new IsNotNull());
+        registerControl("isEmptyString", new IsEmptyString());
         registerControl("isBlank", new IsBlank());
         registerControl("isNonBlank", new IsNonBlank());
         registerControl("isNumeric", new IsNumeric());

main/src/com/google/refine/grel/controls/IsEmptyString.java

@@ -0,0 +1,14 @@
+package com.google.refine.grel.controls;
+
+public class IsEmptyString extends IsTest {
+    @Override
+    protected String getDescription() {
+        return "Returns whether o is an empty string";
+    }
+
+    @Override
+    protected boolean test(Object o) {
+        return o != null && o.getClass().equals(String.class)
+                && o.equals("");
+    }
+}

main/webapp/modules/core/scripts/views/data-table/menu-facets.js

@@ -246,15 +246,29 @@ DataTableColumnHeaderUI.extendMenu(function(column, columnHeaderUI, menu) {
           }
         },
         {
-          id: "core/blank-facet",
+          id: "core/null-facet",
-          label: $.i18n._('core-views')["facet-blank"],
+          label: $.i18n._('core-views')["facet-null"],
           click: function() {
             ui.browsingEngine.addFacet(
                 "list",
                 {
                   "name": column.name,
                   "columnName": column.name,
-                  "expression": "isBlank(value)"
+                  "expression": "isNull(value)"
+                }
+            );
+          }
+        },
+        {
+          id: "core/empty-string-facet",
+          label: $.i18n._('core-views')["facet-empty-string"],
+          click: function() {
+            ui.browsingEngine.addFacet(
+                "list",
+                {
+                  "name": column.name,
+                  "columnName": column.name,
+                  "expression": "isEmptyString(value)"
                 }
             );
           }