add warning mode as well for 2.3

Author: jorisvandenbossche

pandas/core/indexing.py

@@ -2575,11 +2575,21 @@ def __getitem__(self, key):
         return super().__getitem__(key)
 
     def __setitem__(self, key, value) -> None:
-        if not PYPY:
+        if not PYPY and using_copy_on_write():
             if sys.getrefcount(self.obj) <= 2:
                 warnings.warn(
                     _chained_assignment_msg, ChainedAssignmentError, stacklevel=2
                 )
+        elif not PYPY and not using_copy_on_write():
+            ctr = sys.getrefcount(self.obj)
+            ref_count = 2
+            if not warn_copy_on_write() and _check_cacher(self.obj):
+                # see https://github.com/pandas-dev/pandas/pull/56060#discussion_r1399245221
+                ref_count += 1
+            if ctr <= ref_count:
+                warnings.warn(
+                    _chained_assignment_warning_msg, FutureWarning, stacklevel=2
+                )
 
         if self.ndim == 2 and not self._axes_are_unique:
             # GH#33041 fall back to .loc
@@ -2606,11 +2616,21 @@ def _convert_key(self, key):
         return key
 
     def __setitem__(self, key, value) -> None:
-        if not PYPY:
+        if not PYPY and using_copy_on_write():
             if sys.getrefcount(self.obj) <= 2:
                 warnings.warn(
                     _chained_assignment_msg, ChainedAssignmentError, stacklevel=2
                 )
+        elif not PYPY and not using_copy_on_write():
+            ctr = sys.getrefcount(self.obj)
+            ref_count = 2
+            if not warn_copy_on_write() and _check_cacher(self.obj):
+                # see https://github.com/pandas-dev/pandas/pull/56060#discussion_r1399245221
+                ref_count += 1
+            if ctr <= ref_count:
+                warnings.warn(
+                    _chained_assignment_warning_msg, FutureWarning, stacklevel=2
+                )
 
         return super().__setitem__(key, value)
 

pandas/tests/copy_view/test_chained_assignment_deprecation.py

@@ -177,10 +177,10 @@ def test_frame_setitem(indexer, using_copy_on_write):
 @pytest.mark.parametrize(
     "indexer", [0, [0, 1], slice(0, 2), np.array([True, False, True])]
 )
-def test_series_iloc_setitem(indexer, using_copy_on_write):
+def test_series_iloc_setitem(indexer):
     df = DataFrame({"a": [1, 2, 3], "b": 1})
 
-    if using_copy_on_write:
+    with option_context("chained_assignment", "warn"):
         with tm.raises_chained_assignment_error():
             df["a"].iloc[indexer] = 0
 
@@ -191,18 +191,20 @@ def test_series_iloc_setitem(indexer, using_copy_on_write):
 def test_frame_iloc_setitem(indexer, using_copy_on_write):
     df = DataFrame({"a": [1, 2, 3, 4, 5], "b": 1})
 
-    if using_copy_on_write:
-        with tm.raises_chained_assignment_error():
+    extra_warnings = () if using_copy_on_write else (SettingWithCopyWarning,)
+
+    with option_context("chained_assignment", "warn"):
+        with tm.raises_chained_assignment_error(extra_warnings=extra_warnings):
             df[0:3].iloc[indexer] = 10
 
 
 @pytest.mark.parametrize(
     "indexer", [0, [0, 1], slice(0, 2), np.array([True, False, True])]
 )
-def test_series_loc_setitem(indexer, using_copy_on_write):
+def test_series_loc_setitem(indexer):
     df = DataFrame({"a": [1, 2, 3], "b": 1})
 
-    if using_copy_on_write:
+    with option_context("chained_assignment", "warn"):
         with tm.raises_chained_assignment_error():
             df["a"].loc[indexer] = 0
 
@@ -213,38 +215,40 @@ def test_series_loc_setitem(indexer, using_copy_on_write):
 def test_frame_loc_setitem(indexer, using_copy_on_write):
     df = DataFrame({"a": [1, 2, 3, 4, 5], "b": 1})
 
-    if using_copy_on_write:
-        with tm.raises_chained_assignment_error():
+    extra_warnings = () if using_copy_on_write else (SettingWithCopyWarning,)
+
+    with option_context("chained_assignment", "warn"):
+        with tm.raises_chained_assignment_error(extra_warnings=extra_warnings):
             df[0:3].loc[indexer] = 10
 
 
-def test_series_at_setitem(using_copy_on_write):
+def test_series_at_setitem():
     df = DataFrame({"a": [1, 2, 3], "b": 1})
 
-    if using_copy_on_write:
+    with option_context("chained_assignment", "warn"):
         with tm.raises_chained_assignment_error():
             df["a"].at[0] = 0
 
 
-def test_frame_at_setitem(using_copy_on_write):
+def test_frame_at_setitem():
     df = DataFrame({"a": [1, 2, 3, 4, 5], "b": 1})
 
-    if using_copy_on_write:
+    with option_context("chained_assignment", "warn"):
         with tm.raises_chained_assignment_error():
             df[0:3].at[0, "a"] = 10
 
 
-def test_series_iat_setitem(using_copy_on_write):
+def test_series_iat_setitem():
     df = DataFrame({"a": [1, 2, 3], "b": 1})
 
-    if using_copy_on_write:
+    with option_context("chained_assignment", "warn"):
         with tm.raises_chained_assignment_error():
             df["a"].iat[0] = 0
 
 
-def test_frame_iat_setitem(using_copy_on_write):
+def test_frame_iat_setitem():
     df = DataFrame({"a": [1, 2, 3, 4, 5], "b": 1})
 
-    if using_copy_on_write:
+    with option_context("chained_assignment", "warn"):
         with tm.raises_chained_assignment_error():
             df[0:3].iat[0, 0] = 10