Expose Cursor.warning_count

[Copilot]

This ports PyMySQL’s Cursor.warning_count behavior to mysqlclient so callers can inspect whether the last operation produced warnings without issuing an extra round-trip. It also keeps unbuffered cursors in sync once the result stream is fully consumed.

• What changed

  • Added Cursor.warning_count to the base cursor state.
  • Populate it from Connection.warning_count() after each query result is obtained.
  • Reset it at query start to avoid leaking stale values across statements.

• Unbuffered cursor behavior

  • Update SSCursor.warning_count when the result set is exhausted via:
    • fetchone()
    • fetchmany()
    • fetchall()
  • This matches the point at which server-side cursors have fully observed warning state.

• Regression coverage

  • Added focused tests for buffered and unbuffered cursors covering:
    • statement warnings (DROP TABLE IF EXISTS on a missing table)
    • clearing back to 0 on a warning-free statement
    • warning propagation after fully consuming an unbuffered result

cur.execute("DROP TABLE IF EXISTS `no_exists_table`")
assert cur.warning_count == 1

cur.execute("SELECT 1")
assert cur.warning_count == 0