From 166cdbb3e95315e0feb29fb26c6c98837747e22d Mon Sep 17 00:00:00 2001
From: Liang-Chi Hsieh <viirya@gmail.com>
Date: Tue, 6 Mar 2018 07:50:46 +0000
Subject: [PATCH] Remove isDefaultParam.

---
 .../org/apache/spark/ml/tree/treeModels.scala |  4 +-
 .../org/apache/spark/ml/util/ReadWrite.scala  | 45 ++++++++++++-------
 2 files changed, 31 insertions(+), 18 deletions(-)

diff --git a/mllib/src/main/scala/org/apache/spark/ml/tree/treeModels.scala b/mllib/src/main/scala/org/apache/spark/ml/tree/treeModels.scala
index 264a086e7d795..4aa4c3617e7fd 100644
--- a/mllib/src/main/scala/org/apache/spark/ml/tree/treeModels.scala
+++ b/mllib/src/main/scala/org/apache/spark/ml/tree/treeModels.scala
@@ -333,7 +333,7 @@ private[ml] object DecisionTreeModelReadWrite {
 
     // Get impurity to construct ImpurityCalculator for each node
     val impurityType: String = {
-      val impurityJson: JValue = metadata.getParamValue("impurity", isDefaultParam = true)
+      val impurityJson: JValue = metadata.getParamValue("impurity")
       Param.jsonDecode[String](compact(render(impurityJson)))
     }
 
@@ -428,7 +428,7 @@ private[ml] object EnsembleModelReadWrite {
 
     // Get impurity to construct ImpurityCalculator for each node
     val impurityType: String = {
-      val impurityJson: JValue = metadata.getParamValue("impurity", isDefaultParam = true)
+      val impurityJson: JValue = metadata.getParamValue("impurity")
       Param.jsonDecode[String](compact(render(impurityJson)))
     }
 
diff --git a/mllib/src/main/scala/org/apache/spark/ml/util/ReadWrite.scala b/mllib/src/main/scala/org/apache/spark/ml/util/ReadWrite.scala
index 31b4612e33a2a..1a8825df3499d 100644
--- a/mllib/src/main/scala/org/apache/spark/ml/util/ReadWrite.scala
+++ b/mllib/src/main/scala/org/apache/spark/ml/util/ReadWrite.scala
@@ -363,28 +363,41 @@ private[ml] object DefaultParamsReader {
       metadata: JValue,
       metadataJson: String) {
 
+
+    private def getValueFromParams(params: JValue): Seq[(String, JValue)] = {
+      params match {
+        case JObject(pairs) => pairs
+        case _ =>
+          throw new IllegalArgumentException(
+            s"Cannot recognize JSON metadata: $metadataJson.")
+      }
+    }
+
     /**
      * Get the JSON value of the [[org.apache.spark.ml.param.Param]] of the given name.
      * This can be useful for getting a Param value before an instance of `Params`
-     * is available.
-     *
-     * @param isDefaultParam Whether the given param name is a default param. Default is false.
+     * is available. This will look up `params` first, if not existing then looking up
+     * `defaultParams`.
      */
-    def getParamValue(paramName: String, isDefaultParam: Boolean = false): JValue = {
+    def getParamValue(paramName: String): JValue = {
       implicit val format = DefaultFormats
-      val paramsToLookup = if (isDefaultParam) defaultParams else params
-      paramsToLookup match {
-        case JObject(pairs) =>
-          val values = pairs.filter { case (pName, jsonValue) =>
-            pName == paramName
-          }.map(_._2)
-          assert(values.length == 1, s"Expected one instance of Param '$paramName' but found" +
-            s" ${values.length} in JSON Params: " + pairs.map(_.toString).mkString(", "))
-          values.head
-        case _ =>
-          throw new IllegalArgumentException(
-            s"Cannot recognize JSON metadata: $metadataJson.")
+
+      // Looking up for `params` first.
+      var pairs = getValueFromParams(params)
+      var foundPairs = pairs.filter { case (pName, jsonValue) =>
+        pName == paramName
+      }
+      if (foundPairs.length == 0) {
+        // Looking up for `defaultParams` then.
+        pairs = getValueFromParams(defaultParams)
+        foundPairs = pairs.filter { case (pName, jsonValue) =>
+          pName == paramName
+        }
       }
+      assert(foundPairs.length == 1, s"Expected one instance of Param '$paramName' but found" +
+        s" ${foundPairs.length} in JSON Params: " + pairs.map(_.toString).mkString(", "))
+
+      foundPairs.map(_._2).head
     }
 
     /**