Added extraction of score column before node creation

Author: Lynx1820

src/Microsoft.ML.Data/Scorers/SchemaBindablePredictorWrapper.cs

@@ -320,7 +320,7 @@ private protected override bool SaveAsOnnxCore(OnnxContext ctx, RoleMappedSchema
             if (!ctx.ContainsColumn(featName))
                 return false;
             Contracts.Assert(ctx.ContainsColumn(featName));
-            return mapper.SaveAsOnnx(ctx, new[] { outputNames[1] }, ctx.GetVariableName(featName));
+            return mapper.SaveAsOnnx(ctx, outputNames, ctx.GetVariableName(featName));
         }
 
         private protected override ISchemaBoundMapper BindCore(IChannel ch, RoleMappedSchema schema) =>

src/Microsoft.ML.FastTree/FastTree.cs

@@ -3111,7 +3111,8 @@ bool ISingleCanSaveOnnx.SaveAsOnnx(OnnxContext ctx, string[] outputNames, string
             }
 
             string opType = "TreeEnsembleRegressor";
-            var node = ctx.CreateNode(opType, new[] { featureColumn }, outputNames, ctx.GetNodeName(opType));
+            string scoreVarName = (Utils.Size(outputNames) == 2) ? outputNames[1] : outputNames[0]; // Get Score from PredictedLabel and/or Score columns
+            var node = ctx.CreateNode(opType, new[] { featureColumn }, new[] { scoreVarName }, ctx.GetNodeName(opType));
 
             node.AddAttribute("post_transform", PostTransform.None.GetDescription());
             node.AddAttribute("n_targets", 1);

src/Microsoft.ML.StandardTrainers/Standard/LinearModelParameters.cs

@@ -240,10 +240,10 @@ JToken ISingleCanSavePfa.SaveAsPfa(BoundPfaContext ctx, JToken input)
         bool ISingleCanSaveOnnx.SaveAsOnnx(OnnxContext ctx, string[] outputs, string featureColumn)
         {
             Host.CheckValue(ctx, nameof(ctx));
-            Host.Check(Utils.Size(outputs) == 1);
-
             string opType = "LinearRegressor";
-            var node = ctx.CreateNode(opType, new[] { featureColumn }, outputs, ctx.GetNodeName(opType));
+            string scoreVarName = (Utils.Size(outputs) == 2) ? outputs[1] : outputs[0]; // Get Score from PredictedLabel and/or Score columns
+
+            var node = ctx.CreateNode(opType, new[] { featureColumn }, new[] { scoreVarName }, ctx.GetNodeName(opType));
             // Selection of logit or probit output transform. enum {'NONE', 'LOGIT', 'PROBIT}
             node.AddAttribute("post_transform", "NONE");
             node.AddAttribute("targets", 1);

test/Microsoft.ML.Tests/OnnxConversionTest.cs

@@ -240,7 +240,6 @@ public void binaryClassificationTrainersOnnxConversionTest()
                     CompareSelectedR4ScalarColumns(transformedData.Schema[5].Name, outputNames[3], transformedData, onnxResult, 3);
                     CompareSelectedScalarColumns<Boolean>(transformedData.Schema[4].Name, outputNames[2], transformedData, onnxResult);
                 }
-
             }
             Done();
         }