Checking the sanity of supervised learning model schemas. Fixes #47

src/main/java/org/jpmml/sparkml/ModelConverter.java

@@ -156,6 +156,8 @@ public Schema encodeSchema(SparkMLEncoder encoder){
 
 		Schema result = new Schema(label, features);
 
+		SchemaUtil.checkSchema(result);
+
 		return result;
 	}
 

src/main/java/org/jpmml/sparkml/SchemaUtil.java

@@ -19,15 +19,34 @@
 package org.jpmml.sparkml;
 
 import java.util.List;
+import java.util.Objects;
 
 import org.jpmml.converter.CategoricalLabel;
 import org.jpmml.converter.Feature;
+import org.jpmml.converter.Label;
+import org.jpmml.converter.Schema;
 
 public class SchemaUtil {
 
 	private SchemaUtil(){
 	}
 
+	static
+	public void checkSchema(Schema schema){
+		Label label = schema.getLabel();
+		List<? extends Feature> features = schema.getFeatures();
+
+		if(label != null){
+
+			for(Feature feature : features){
+
+				if(Objects.equals(label.getName(), feature.getName())){
+					throw new IllegalArgumentException("Label column '" + label.getName() + "' is contained in the list of feature columns");
+				}
+			}
+		}
+	}
+
 	static
 	public void checkSize(int size, CategoricalLabel categoricalLabel){
 

src/main/java/org/jpmml/sparkml/SparkMLEncoder.java

@@ -59,21 +59,6 @@ public boolean hasFeatures(String column){
 		return this.columnFeatures.containsKey(column);
 	}
 
-	public List<Feature> getSchemaFeatures(){
-		StructType schema = getSchema();
-
-		List<Feature> result = new ArrayList<>();
-
-		StructField[] fields = schema.fields();
-		for(StructField field : fields){
-			Feature feature = getOnlyFeature(field.name());
-
-			result.add(feature);
-		}
-
-		return result;
-	}
-
 	public Feature getOnlyFeature(String column){
 		List<Feature> features = getFeatures(column);
 
@@ -149,7 +134,7 @@ public void putFeatures(String column, List<Feature> features){
 				Feature feature = features.get(i);
 
 				if(!(feature.getName()).equals(existingFeature.getName())){
-					throw new IllegalArgumentException("Expected '" + existingFeature.getName() + "' feature, got '" + feature.getName() + "' feature");
+					throw new IllegalArgumentException("Expected feature column '" + existingFeature.getName() + "', got feature column '" + feature.getName() + "'");
 				}
 			}
 		}