Avoid NPE when casting empty strings to ints

integration_tests/src/main/python/cast_test.py

@@ -0,0 +1,32 @@
+# Copyright (c) 2021, NVIDIA CORPORATION.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+import pytest
+
+from asserts import assert_gpu_and_cpu_are_equal_collect, assert_gpu_and_cpu_are_equal_sql, assert_gpu_and_cpu_error
+from data_gen import *
+from functools import reduce
+from spark_session import is_before_spark_311
+from marks import allow_non_gpu
+from pyspark.sql.types import *
+from pyspark.sql.functions import array_contains, col, first, isnan, lit, element_at
+
+def test_cast_empty_string_to_int():
+    assert_gpu_and_cpu_are_equal_collect(
+            lambda spark : unary_op_df(spark, StringGen(pattern="")).selectExpr(
+                'CAST(a as BYTE)',
+                'CAST(a as SHORT)',
+                'CAST(a as INTEGER)',
+                'CAST(a as LONG)'))
+

sql-plugin/src/main/scala/com/nvidia/spark/rapids/GpuCast.scala

@@ -670,12 +670,17 @@ case class GpuCast(
       // To avoid doing the expensive regex all the time, we will first check to see if we need
       // to do it. The only time we do need to do it is when we have a '.' in any of the strings.
       val data = input.getData
-      val hasDot = withResource(
-        ColumnView.fromDeviceBuffer(data, 0, DType.INT8, data.getLength.toInt)) { childData =>
-        withResource(GpuScalar.from('.'.toByte, ByteType)) { dot =>
-          childData.contains(dot)
+      val hasDot = if (data != null) {
+        withResource(
+          ColumnView.fromDeviceBuffer(data, 0, DType.INT8, data.getLength.toInt)) { childData =>
+          withResource(GpuScalar.from('.'.toByte, ByteType)) { dot =>
+            childData.contains(dot)
+          }
         }
+      } else {
+        false
       }
+
       if (hasDot) {
         withResource(input.extractRe("^([+\\-]?[0-9]+)(?:\\.[0-9]*)?$")) { table =>
           table.getColumn(0).incRefCount()