Reject non-positive Cursor.arraysize

ISSUE-33 — cursor.arraysize = 0 (or a negative number) used to make
fetchmany() silently return [] because the implementation loops
range(size). Users expect either an error or a sensible default;
silent empty returns make this a debugging trap. Now the setter
raises ProgrammingError on value < 1, matching the convention used
by psycopg and asyncpg.

Applied to both sync Cursor and AsyncCursor.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: antoineleclair

src/dqlitedbapi/aio/cursor.py

@@ -55,6 +55,10 @@ def arraysize(self) -> int:
 
     @arraysize.setter
     def arraysize(self, value: int) -> None:
+        if value < 1:
+            from dqlitedbapi.exceptions import ProgrammingError
+
+            raise ProgrammingError(f"arraysize must be >= 1, got {value}")
         self._arraysize = value
 
     def _check_closed(self) -> None:

src/dqlitedbapi/cursor.py

@@ -169,6 +169,8 @@ def arraysize(self) -> int:
 
     @arraysize.setter
     def arraysize(self, value: int) -> None:
+        if value < 1:
+            raise ProgrammingError(f"arraysize must be >= 1, got {value}")
         self._arraysize = value
 
     def _check_closed(self) -> None:

tests/test_arraysize_validation.py

@@ -0,0 +1,44 @@
+"""Cursor.arraysize rejects non-positive values (ISSUE-33)."""
+
+import pytest
+
+from dqlitedbapi.aio.connection import AsyncConnection
+from dqlitedbapi.aio.cursor import AsyncCursor
+from dqlitedbapi.connection import Connection
+from dqlitedbapi.cursor import Cursor
+from dqlitedbapi.exceptions import ProgrammingError
+
+
+class TestArraysizeValidation:
+    def _sync_cursor(self) -> Cursor:
+        conn = Connection("localhost:19001", timeout=2.0)
+        return Cursor(conn)
+
+    def _async_cursor(self) -> AsyncCursor:
+        conn = AsyncConnection("localhost:19001")
+        return AsyncCursor(conn)
+
+    def test_zero_rejected_sync(self) -> None:
+        c = self._sync_cursor()
+        with pytest.raises(ProgrammingError, match=">= 1"):
+            c.arraysize = 0
+
+    def test_negative_rejected_sync(self) -> None:
+        c = self._sync_cursor()
+        with pytest.raises(ProgrammingError, match=">= 1"):
+            c.arraysize = -5
+
+    def test_positive_accepted_sync(self) -> None:
+        c = self._sync_cursor()
+        c.arraysize = 10
+        assert c.arraysize == 10
+
+    def test_zero_rejected_async(self) -> None:
+        c = self._async_cursor()
+        with pytest.raises(ProgrammingError, match=">= 1"):
+            c.arraysize = 0
+
+    def test_negative_rejected_async(self) -> None:
+        c = self._async_cursor()
+        with pytest.raises(ProgrammingError, match=">= 1"):
+            c.arraysize = -1