Add fromCategories helper

src/EventStore.Projections.Core.Tests/Services/v8/when_defining_a_v8_projection.cs

@@ -116,6 +116,62 @@ public void source_definition_is_correct()
             }
         }
 
+        [TestFixture]
+        public class with_multiple_from_categories : TestFixtureWithJsProjection
+        {
+            protected override void Given()
+            {
+                _projection = @"
+                    fromCategories(['category1', 'category2', 'category3']).when({
+                    $any: function(state, event) {
+                            return state;
+                        }});
+                ";
+                _state = @"{""count"": 0}";
+            }
+
+            [Test, Category("v8")]
+            public void source_definition_is_correct()
+            {
+                Assert.AreEqual(false, _source.AllStreams);
+                Assert.IsNotNull(_source.Streams);
+                Assert.AreEqual(3, _source.Streams.Length);
+                Assert.AreEqual("$ce-category1", _source.Streams[0]);
+                Assert.AreEqual("$ce-category2", _source.Streams[1]);
+                Assert.AreEqual("$ce-category3", _source.Streams[2]);
+                Assert.That(_source.Categories == null || _source.Categories.Length == 0);
+                Assert.AreEqual(false, _source.ByStreams);
+            }
+        }
+
+        [TestFixture]
+        public class with_multiple_from_categories_plain : TestFixtureWithJsProjection
+        {
+            protected override void Given()
+            {
+                _projection = @"
+                    fromCategories('category1', 'category2', 'category3').when({
+                        $any:function(state, event) {
+                            return state;
+                        }});
+                ";
+                _state = @"{""count"": 0}";
+            }
+
+            [Test, Category("v8")]
+            public void source_definition_is_correct()
+            {
+                Assert.AreEqual(false, _source.AllStreams);
+                Assert.IsNotNull(_source.Streams);
+                Assert.AreEqual(3, _source.Streams.Length);
+                Assert.AreEqual("$ce-category1", _source.Streams[0]);
+                Assert.AreEqual("$ce-category2", _source.Streams[1]);
+                Assert.AreEqual("$ce-category3", _source.Streams[2]);
+                Assert.That(_source.Categories == null || _source.Categories.Length == 0);
+                Assert.AreEqual(false, _source.ByStreams);
+            }
+        }
+
         [TestFixture]
         public class with_from_category : TestFixtureWithJsProjection
         {

src/EventStore.Projections.Core/Prelude/1Prelude.js

@@ -210,6 +210,14 @@ function scope($on, $notify) {
         };
     }
 
+    function fromCategories(categories) {
+        var arr = Array.isArray(categories) ? categories : Array.prototype.slice.call(arguments);
+        arr = arr.map(function (x) {
+            return '$ce-' + x;
+        });
+        return fromStreams(arr);
+    }
+
     function emit(streamId, eventName, eventBody, metadata) {
         var message = { streamId: streamId, eventName: eventName , body: JSON.stringify(eventBody), metadata: metadata, isJson: true };
         eventProcessor.emit(message);
@@ -257,6 +265,7 @@ function scope($on, $notify) {
         fromCategory: fromCategory,
         fromStream: fromStream,
         fromStreams: fromStreams,
+        fromCategories: fromCategories,
         fromStreamCatalog: fromStreamCatalog,
         fromStreamsMatching: fromStreamsMatching,