Fix fake schema's creation and add a test (#2331)

Author: wschin

src/Microsoft.ML.Data/DataLoadSave/FakeSchema.cs

@@ -29,15 +29,15 @@ public static Schema Create(SchemaShape shape)
                 var partialMetadata = shape[i].Metadata;
                 for (int j = 0; j < partialMetadata.Count; ++j)
                 {
-                    var metaColumnType = MakeColumnType(partialMetadata[i]);
+                    var metaColumnType = MakeColumnType(partialMetadata[j]);
                     Delegate del;
                     if (metaColumnType is VectorType vectorType)
                         del = Utils.MarshalInvoke(GetDefaultVectorGetter<int>, vectorType.ItemType.RawType);
                     else
                         del = Utils.MarshalInvoke(GetDefaultGetter<int>, metaColumnType.RawType);
                     metaBuilder.Add(partialMetadata[j].Name, metaColumnType, del);
                 }
-                builder.AddColumn(shape[i].Name, MakeColumnType(shape[i]));
+                builder.AddColumn(shape[i].Name, MakeColumnType(shape[i]), metaBuilder.GetMetadata());
             }
             return builder.GetSchema();
         }

test/Microsoft.ML.Tests/FakeSchemaTest.cs

@@ -0,0 +1,59 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using Microsoft.Data.DataView;
+using Microsoft.ML.Core.Data;
+using Microsoft.ML.Data;
+using Microsoft.ML.Data.DataLoadSave;
+using Microsoft.ML.TestFramework;
+using Xunit;
+using Xunit.Abstractions;
+
+namespace Microsoft.ML.Tests
+{
+    public class FakeSchemaTest : BaseTestClass
+    {
+        public FakeSchemaTest(ITestOutputHelper output)
+            : base(output)
+        {
+        }
+
+        [Fact]
+        void SimpleTest()
+        {
+            var metadataBuilder = new MetadataBuilder();
+            metadataBuilder.Add("M", NumberType.R4, (ref float v) => v = 484f);
+            var schemaBuilder = new SchemaBuilder();
+            schemaBuilder.AddColumn("A", new VectorType(NumberType.R4, 94));
+            schemaBuilder.AddColumn("B", new KeyType(typeof(uint), 17));
+            schemaBuilder.AddColumn("C", NumberType.I4, metadataBuilder.GetMetadata());
+
+            var shape = SchemaShape.Create(schemaBuilder.GetSchema());
+
+            var fakeSchema = FakeSchemaFactory.Create(shape);
+
+            var columnA = fakeSchema[0];
+            var columnB = fakeSchema[1];
+            var columnC = fakeSchema[2];
+
+            Assert.Equal("A", columnA.Name);
+            Assert.Equal(NumberType.R4, columnA.Type.GetItemType());
+            Assert.Equal(10, columnA.Type.GetValueCount());
+
+            Assert.Equal("B", columnB.Name);
+            Assert.Equal(DataKind.U4, columnB.Type.GetRawKind());
+            Assert.Equal(10u, columnB.Type.GetKeyCount());
+
+            Assert.Equal("C", columnC.Name);
+            Assert.Equal(NumberType.I4, columnC.Type);
+
+            var metaC = columnC.Metadata;
+            Assert.Single(metaC.Schema);
+
+            float mValue = -1;
+            metaC.GetValue("M", ref mValue);
+            Assert.Equal(default, mValue);
+        }
+    }
+}

test/Microsoft.ML.Tests/TextLoaderTests.cs

@@ -11,7 +11,6 @@
 using Microsoft.ML.Model;
 using Microsoft.ML.RunTests;
 using Microsoft.ML.TestFramework;
-using Microsoft.ML.Transforms.Conversions;
 using Newtonsoft.Json.Linq;
 using Xunit;
 using Xunit.Abstractions;