Deprecate Connection.set_charset() at runtime and document warning behavior (#1243)

Copilot · web-flow · commit 637fe7e6b2b1 · 2026-05-19T13:43:39.000+09:00
`Connection.set_charset(charset)` was marked for future removal but did
not emit a deprecation signal at call time. This change adds runtime
deprecation signaling and updates release notes accordingly.
diff --git a/CHANGELOG.md b/CHANGELOG.md
@@ -32,6 +32,7 @@ Release date: TBD
 * Support MySQL 8 row/column alias syntax in `executemany` INSERT regex. (#1235)
 * Expose SQLSTATE on MySQL protocol exceptions without changing exception formatting. (#1236)
 * Reject non-finite `decimal.Decimal` query parameters (`NaN`, `sNaN`, `±Infinity`). (#1237)
+* `Connection.set_charset(charset)` now emits `DeprecationWarning`.
 
 ## v1.1.3
 
diff --git a/pymysql/connections.py b/pymysql/connections.py
@@ -630,6 +630,11 @@ def ping(self, reconnect=False):
 
     def set_charset(self, charset):
         """Deprecated. Use set_character_set() instead."""
+        warnings.warn(
+            "'set_charset' is deprecated, use 'set_character_set' instead",
+            DeprecationWarning,
+            2,
+        )
         # This function has been implemented in old PyMySQL.
         # But this name is different from MySQLdb.
         # So we keep this function for compatibility and add
diff --git a/pymysql/tests/test_err.py b/pymysql/tests/test_err.py
@@ -1,5 +1,8 @@
 import pytest
+from unittest import mock
+
 from pymysql import err
+from pymysql.connections import Connection
 
 
 def test_error_init_sqlstate():
@@ -26,3 +29,13 @@ def test_raise_mysql_exception():
     assert cm.type == err.OperationalError
     assert cm.value.args == (1040, "Too many connections")
     assert cm.value.sqlstate is None
+
+
+def test_set_charset_deprecated():
+    con = mock.Mock(spec=Connection)
+    with pytest.warns(
+        DeprecationWarning,
+        match="'set_charset' is deprecated, use 'set_character_set' instead",
+    ):
+        Connection.set_charset(con, "utf8mb4")
+    con.set_character_set.assert_called_once_with("utf8mb4")
