Fix issue with non-nan values for null float columns (#72)

Author: peytondmurray

src/npcontainer.cpp

@@ -329,7 +329,7 @@ fill_NAvalue(void *value, PyArray_Descr *dtype)
 {
     switch (dtype->type_num) {
         case NPY_BOOL:
-            ((npy_bool *)value)[0] = 0;  // XXX False is a good default?
+            ((npy_bool *)value)[0] = 0;  // Make this False to match `bool(None)` in Python
             break;
         case NPY_BYTE:
             ((npy_byte *)value)[0] = NPY_MAX_BYTE;
@@ -368,10 +368,10 @@ fill_NAvalue(void *value, PyArray_Descr *dtype)
             ((npy_float *)value)[0] = NPY_NANF;
             break;
         case NPY_DOUBLE:
-            ((npy_float *)value)[0] = NPY_NAN;
+            ((npy_double *)value)[0] = NPY_NAN;
             break;
         case NPY_LONGDOUBLE:
-            ((npy_float *)value)[0] = NPY_NANL;
+            ((npy_longdouble *)value)[0] = NPY_NANL;
             break;
         case NPY_CFLOAT:
             ((npy_cfloat *)value)[0] = {NPY_NANF, NPY_NANF};

tests/test_numpy.py

@@ -3,12 +3,13 @@
 from typing import Optional
 
 import hypothesis.strategies as st
-import npyodbc
 import numpy as np
 import pytest
 from hypothesis import given, reject, settings
 from numpy.testing import assert_allclose, assert_array_equal
 
+import npyodbc
+
 
 @pytest.fixture(scope="module")
 def connection() -> npyodbc.Connection:
@@ -349,3 +350,27 @@ def test_fetchdictarray_coercion(cursor, int_dtype, float_dtype, values):
     )
 
     cleanup(cursor)
+
+
+def test_null_floats(cursor):
+    """Test that writing null values into a float column are NaN when retrieved."""
+    cursor.execute("CREATE TABLE t (f FLOAT NULL);")
+    cursor.execute("INSERT INTO t VALUES (123.12345678), (NULL);")
+    res = cursor.execute("SELECT * FROM t;").fetchdictarray(null_suffix="_isnull")
+
+    assert_array_equal(res['f'], [123.12345678, np.nan])
+    assert_array_equal(res['f_isnull'], [False, True])
+
+    cleanup(cursor)
+
+
+def test_null_strings(cursor):
+    """Test that null values in a text column are empty strings when retrieved."""
+    cursor.execute("CREATE TABLE t (f TEXT NULL);")
+    cursor.execute("INSERT INTO t VALUES ('foo'), (NULL);")
+    res = cursor.execute("SELECT * FROM t;").fetchdictarray(null_suffix="_isnull")
+
+    assert_array_equal(res['f'], ['foo', ''])
+    assert_array_equal(res['f_isnull'], [False, True])
+
+    cleanup(cursor)