bpo-43368: Fix fetching empty bytes in sqlite3 (GH-24706)

Regression introduced in 47feb1f.

Author: felixxm

Lib/sqlite3/test/regression.py

@@ -409,6 +409,10 @@ def log(self, *args):
             self.con.execute("select 1")  # trigger seg fault
             method(None)
 
+    def test_return_empty_bytestring(self):
+        cur = self.con.execute("select X''")
+        val = cur.fetchone()[0]
+        self.assertEqual(val, b'')
 
 
 def suite():

Misc/NEWS.d/next/Library/2021-03-02-13-45-05.bpo-43368.t9XEkQ.rst

@@ -0,0 +1,2 @@
+Fix a regression introduced in GH-24562, where an empty bytestring was fetched
+as ``None`` instead of ``b''`` in :mod:`sqlite3`. Patch by Mariusz Felisiak.

Modules/_sqlite/cursor.c

@@ -333,12 +333,8 @@ _pysqlite_fetch_one_row(pysqlite_Cursor* self)
             } else {
                 /* coltype == SQLITE_BLOB */
                 const char *blob = sqlite3_column_blob(self->statement->st, i);
-                if (!blob) {
-                    converted = Py_NewRef(Py_None);
-                } else {
-                    nbytes = sqlite3_column_bytes(self->statement->st, i);
-                    converted = PyBytes_FromStringAndSize(blob, nbytes);
-                }
+                nbytes = sqlite3_column_bytes(self->statement->st, i);
+                converted = PyBytes_FromStringAndSize(blob, nbytes);
             }
         }