[SPARK-18772][SQL] NaN/Infinite float parsing in JSON is inconsistent

sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/json/JacksonParser.scala

@@ -88,6 +88,17 @@ class JacksonParser(
     }
   }
 
+  private object SpecialDouble {
+    def unapply(value: String): Option[Double] = {
+      value.toLowerCase match {
+        case "nan" => Some(Double.NaN)
+        case "infinity" | "+infinity" | "inf" | "+inf" => Some(Double.PositiveInfinity)
+        case "-infinity" | "-inf" => Some(Double.NegativeInfinity)
+        case _ => None
+      }
+    }
+  }
+
   /**
    * Create a converter which converts the JSON documents held by the `JsonParser`
    * to a value according to a desired schema.

sql/core/src/test/scala/org/apache/spark/sql/execution/datasources/json/JsonSuite.scala

@@ -1986,6 +1986,37 @@ class JsonSuite extends QueryTest with SharedSQLContext with TestJsonData {
           .collect
       }.getMessage
       assert(errMsg.startsWith("The field for corrupt records must be string type and nullable"))
+
+  test("SPARK-18772: Special floats") {
+    val records = sparkContext
+      .parallelize(
+        """{"a": "NaN"}""" ::
+          """{"a": "nAn"}""" ::
+          """{"a": "-iNf"}""" ::
+          """{"a": "inF"}""" ::
+          """{"a": "+Inf"}""" ::
+          """{"a": "-iNfInity"}""" ::
+          """{"a": "InFiNiTy"}""" ::
+          """{"a": "+InfiNitY"}""" ::
+          """{"a": "+Infi"}""" ::
+          Nil)
+
+    for (dt <- Seq(FloatType, DoubleType)) {
+      val res = spark.read
+        .schema(StructType(Seq(StructField("a", dt))))
+        .json(records)
+        .select($"a".cast(DoubleType).as[java.lang.Double])
+        .collect()
+      assert(res.length === 9)
+      assert(res(0).isNaN)
+      assert(res(1).isNaN)
+      assert(res(2).toDouble.isNegInfinity)
+      assert(res(3).toDouble.isPosInfinity)
+      assert(res(4).toDouble.isPosInfinity)
+      assert(res(5).toDouble.isNegInfinity)
+      assert(res(6).toDouble.isPosInfinity)
+      assert(res(7).toDouble.isPosInfinity)
+      assert(res(8) eq null)
     }
   }
 }