Nadrop (dotnet#1810)

* Fix MissingValueDroppingTransformer bug

* Add unit test

* Add baseline

Author: yaeldMS

src/Microsoft.ML.Transforms/MissingValueDroppingTransformer.cs

@@ -204,7 +204,7 @@ protected override Delegate MakeGetter(IRow input, int iinfo, Func<int, bool> ac
 
             private ValueGetter<VBuffer<TDst>> MakeVecGetter<TDst>(IRow input, int iinfo)
             {
-                var srcGetter = input.GetGetter<VBuffer<TDst>>(iinfo);
+                var srcGetter = input.GetGetter<VBuffer<TDst>>(_srcCols[iinfo]);
                 var buffer = default(VBuffer<TDst>);
                 var isNA = (InPredicate<TDst>)_isNAs[iinfo];
                 var def = default(TDst);

test/BaselineOutput/Common/SavePipe/SavePipeDropNAs-Data.txt

@@ -0,0 +1,17 @@
+#@ TextLoader{
+#@   header+
+#@   sep=tab
+#@   col=Num:R4:0-1
+#@   col=Sep:TX:2
+#@   col=NumNAsDropped:R4:3-**
+#@   col={name=Sep2 type=TX src={ min=-1}}
+#@   col={name=Text type=TX src={ min=-1 var=+}}
+#@   col={name=Sep3 type=TX src={ min=-1}}
+#@   col={name=TextNAsDropped type=U4 src={ min=-1 var=+} key=0-3}
+#@ }
+""	""	Sep	Sep2	Sep3
+2	0	|	2	0	|	Hello	World!	|	0
+3	4	|	3	4	|	|
+0	?	|	0	|	Bye	all	|	3	1
+7	8	|	7	8	|	Good	bye	|	2
+?	?	|	|	this	is	a	|

test/Microsoft.ML.TestFramework/DataPipe/TestDataPipe.cs

@@ -785,6 +785,35 @@ public void SavePipeTokenizerAndStopWords()
             Done();
         }
 
+        [Fact]
+        public void SavePipeDropNAs()
+        {
+            string pathData = DeleteOutputPath("SavePipe", "DropNAs.txt");
+            File.WriteAllLines(pathData,
+                new[]
+                {
+                    "2,0,|,Hello World!",
+                    "3,4,|,",
+                    "0,nan,|,Bye all",
+                    "7,8,|,Good bye",
+                    "?,nan,|,this is a"
+                });
+
+            TestCore(pathData, false,
+                new[]
+                {
+                    "loader=Text{header- sep=, col=Num:R4:0-1 col=Sep:TX:2 col=Text:TX:3}",
+                    "xf=NADrop{col=NumNAsDropped:Num}",
+                    "xf=Token{col=Text}",
+                    "xf=Term{col=Text2:Text terms=Hello,all,Good,Bye}",
+                    "xf=NADrop{col=TextNAsDropped:Text2}",
+                    "xf=Copy{col=Sep2:Sep col=Sep3:Sep}",
+                    "xf=Select{keepcol=Num keepcol=Sep keepcol=NumNAsDropped keepcol=Sep2 keepcol=Text keepcol=Sep3 keepcol=TextNAsDropped}"
+                }, baselineSchema: false, roundTripText: false);
+
+            Done();
+        }
+
         [Fact]
         public void TestHashTransformFloat()
         {