Add .slt tests

Author: shivbhatia10

datafusion/spark/src/function/math/isnan.rs

@@ -30,8 +30,10 @@ use datafusion_expr::{
 /// Spark-compatible `isnan` expression
 /// <https://spark.apache.org/docs/latest/api/sql/index.html#isnan>
 ///
-/// Differences with standard SQL:
-///  - Returns `false` for NULL inputs (not NULL)
+/// Differences with DataFusion isnan:
+///  - Spark returns `false` for NULL inputs; DataFusion propagates NULL
+///  - Spark only accepts Float32 and Float64; DataFusion accepts all numeric
+///    types (returning false for integers and decimals, which are never NaN)
 #[derive(Debug, PartialEq, Eq, Hash)]
 pub struct SparkIsNaN {
     signature: Signature,

datafusion/sqllogictest/test_files/spark/math/isnan.slt

@@ -0,0 +1,64 @@
+# Licensed to the Apache Software Foundation (ASF) under one
+# or more contributor license agreements.  See the NOTICE file
+# distributed with this work for additional information
+# regarding copyright ownership.  The ASF licenses this file
+# to you 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.
+
+# This file is part of the implementation of the datafusion-spark function library.
+# For more information, please see:
+#   https://github.com/apache/datafusion/issues/15914
+
+# Scalar input: float64
+query BBBBB
+SELECT isnan(1.0::DOUBLE), isnan('NaN'::DOUBLE), isnan('inf'::DOUBLE), isnan(0.0::DOUBLE), isnan(-1.0::DOUBLE);
+----
+false true false false false
+
+# Scalar input: float64 NULL returns false (Spark behaviour, not NULL)
+query B
+SELECT isnan(NULL::DOUBLE);
+----
+false
+
+# Scalar input: float32
+query BBBBB
+SELECT isnan(1.0::FLOAT), isnan('NaN'::FLOAT), isnan('inf'::FLOAT), isnan(0.0::FLOAT), isnan(-1.0::FLOAT);
+----
+false true false false false
+
+# Scalar input: float32 NULL returns false
+query B
+SELECT isnan(NULL::FLOAT);
+----
+false
+
+# Array input: float64 — NULL produces false, not NULL
+query B
+SELECT isnan(a) FROM (VALUES (1.0::DOUBLE), ('NaN'::DOUBLE), (NULL::DOUBLE), ('inf'::DOUBLE), (0.0::DOUBLE)) AS t(a);
+----
+false
+true
+false
+false
+false
+
+# Array input: float32
+query B
+SELECT isnan(a) FROM (VALUES (1.0::FLOAT), ('NaN'::FLOAT), (NULL::FLOAT), ('inf'::FLOAT), (0.0::FLOAT)) AS t(a);
+----
+false
+true
+false
+false
+false