Close execute_write returning cursor on fetch errors

Refs #2762

datasette/database.py

@@ -908,16 +908,18 @@ class ExecuteWriteResult:
         truncated = False
         description = cursor.description
         lastrowid = cursor.lastrowid
-        if description is not None:
-            if return_all:
-                rows = cursor.fetchall()
-            else:
-                rows = cursor.fetchmany(returning_limit + 1)
-                if len(rows) > returning_limit:
-                    rows = rows[:returning_limit]
-                    truncated = True
-        rowcount = cursor.rowcount
-        cursor.close()
+        try:
+            if description is not None:
+                if return_all:
+                    rows = cursor.fetchall()
+                else:
+                    rows = cursor.fetchmany(returning_limit + 1)
+                    if len(rows) > returning_limit:
+                        rows = rows[:returning_limit]
+                        truncated = True
+            rowcount = cursor.rowcount
+        finally:
+            cursor.close()
         if description is not None and not return_all and truncated and rowcount == 0:
             rowcount = -1
         return cls(rowcount, lastrowid, description, rows, truncated)

tests/test_internals_database.py

@@ -5,7 +5,7 @@ Tests for the datasette.database.Database class
 import asyncio
 from types import SimpleNamespace
 from datasette.app import Datasette
-from datasette.database import Database, Results, MultipleValues
+from datasette.database import Database, ExecuteWriteResult, Results, MultipleValues
 from datasette.database import DatasetteClosedError
 from datasette.database import _deliver_write_result
 from datasette.utils.sqlite import sqlite3
@@ -628,6 +628,29 @@ async def test_execute_write_with_returning_block_false(db):
     ).single_value() == "Cleo"
 
 
+def test_execute_write_result_closes_cursor_on_fetch_error():
+    class Cursor:
+        description = (("id", None, None, None, None, None, None),)
+        lastrowid = 1
+        rowcount = 0
+
+        def __init__(self):
+            self.closed = False
+
+        def fetchmany(self, size):
+            raise sqlite3.DatabaseError("fetch failed")
+
+        def close(self):
+            self.closed = True
+
+    cursor = Cursor()
+
+    with pytest.raises(sqlite3.DatabaseError):
+        ExecuteWriteResult.from_cursor(cursor)
+
+    assert cursor.closed is True
+
+
 @pytest.mark.asyncio
 async def test_execute_write_script(db):
     await db.execute_write_script(