Some style improvements

Also add `.idea` to `.gitignore`.

.gitignore

@@ -21,6 +21,7 @@
 
 # Generic editors
 .vscode
+.idea
 
 # Common things
 *~

src/core/test/base/src/main/scala/TestBase.scala

@@ -42,6 +42,7 @@ abstract class TestBase extends FunSuite with BeforeAndAfterEachTestData with Be
 
   protected lazy val sc: SparkContext = session.sparkContext
   protected lazy val dir = SparkSessionFactory.workingDir
+
   protected def normalizePath(path: String) = SparkSessionFactory.customNormalize(path)
 
   // Timing info
@@ -117,7 +118,7 @@ abstract class TestBase extends FunSuite with BeforeAndAfterEachTestData with Be
     val df = Seq(
       (0, "guitars", "drums"),
       (1, "piano", "trumpet"),
-      (2, "bass", "cymbals")).toDF("numbers","words", "more")
+      (2, "bass", "cymbals")).toDF("numbers", "words", "more")
     df
   }
 

src/find-best-model/src/main/scala/FindBestModel.scala

@@ -135,7 +135,7 @@ class FindBestModel(override val uid: String) extends Estimator[BestModel] with
           case _ => throw new Exception("Model type not supported for evaluation")
         }
       }
-      parameters += getModelParams(model).toSeq.map { case pv => s"${pv.param.name}: ${pv.value}" }.mkString(", ")
+      parameters += getModelParams(model).toSeq.map(pv => s"${pv.param.name}: ${pv.value}").mkString(", ")
       if (bestMetric.isNaN || operator(currentMetric, bestMetric)) {
         bestMetric = currentMetric
         selectedModel = model

src/text-featurizer/src/test/scala/TextFeaturizerSpec.scala

@@ -83,4 +83,5 @@ class TextFeaturizerSpec extends EstimatorFuzzingTest {
   override def getEstimator(): Estimator[_] = new TextFeaturizer()
 
   override def schemaForDataset: StructType = new StructType(Array(StructField(inputCol, StringType, false)))
+
 }

src/train-regressor/src/main/scala/TrainRegressor.scala

@@ -64,7 +64,7 @@ class TrainRegressor(override val uid: String) extends Estimator[TrainedRegresso
           .setLabelCol(labelColumn)
           .setFeaturesCol(featuresColumn).asInstanceOf[Estimator[_ <: PipelineStage]]
       }
-      case default @ defaultType if defaultType.isInstanceOf[Estimator[_ <: PipelineStage]] => {
+      case default@defaultType if defaultType.isInstanceOf[Estimator[_ <: PipelineStage]] => {
         // assume label col and features col already set
         default
       }

src/train-regressor/src/test/scala/VerifyTrainRegressor.scala

@@ -142,7 +142,7 @@ class VerifyTrainRegressor extends EstimatorFuzzingTest {
 /** Test helper methods for Train Regressor module. */
 object TrainRegressorTestUtilities {
 
-  def createLinearRegressor(labelColumn: String): Estimator[TrainedRegressorModel] = {
+  def createLinearRegressor(labelColumn: String): TrainRegressor = {
     val linearRegressor = new LinearRegression()
       .setRegParam(0.3)
       .setElasticNetParam(0.8)
@@ -152,7 +152,7 @@ object TrainRegressorTestUtilities {
       .set(trainRegressor.labelCol, labelColumn)
   }
 
-  def createRandomForestRegressor(labelColumn: String): Estimator[TrainedRegressorModel] = {
+  def createRandomForestRegressor(labelColumn: String): TrainRegressor = {
     val linearRegressor = new RandomForestRegressor()
       .setFeatureSubsetStrategy("auto")
       .setMaxBins(32)