bpo-44089: Allow subclassing of csv.Error (GH-26008) (GH-26066)

* fix subclass error * Update 2021-05-09-22-52-34.bpo-44089.IoANsN.rst (cherry picked from commit 2b458c1) Co-authored-by: Ken Jin <28750310+Fidget-Spinner@users.noreply.github.com> Co-authored-by: Ken Jin <28750310+Fidget-Spinner@users.noreply.github.com>
python · May 12, 2021 · 3e44e9a · 3e44e9a
1 parent 48cb11b
commit 3e44e9a
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diff --git a/Lib/test/test_csv.py b/Lib/test/test_csv.py
@@ -1237,6 +1237,9 @@ def test__all__(self):
         extra = {'__doc__', '__version__'}
         support.check__all__(self, csv, ('csv', '_csv'), extra=extra)
 
+    def test_subclassable(self):
+        # issue 44089
+        class Foo(csv.Error): ...
 
 if __name__ == '__main__':
     unittest.main()
diff --git a/Misc/NEWS.d/next/Library/2021-05-09-22-52-34.bpo-44089.IoANsN.rst b/Misc/NEWS.d/next/Library/2021-05-09-22-52-34.bpo-44089.IoANsN.rst
@@ -0,0 +1,2 @@
+Allow subclassing ``csv.Error`` in 3.10 (it was allowed in 3.9 and earlier but
+was disallowed in early versions of 3.10).
diff --git a/Modules/_csv.c b/Modules/_csv.c
@@ -1515,7 +1515,7 @@ static PyType_Slot error_slots[] = {
 
 PyType_Spec error_spec = {
     .name = "_csv.Error",
-    .flags = Py_TPFLAGS_DEFAULT,
+    .flags = Py_TPFLAGS_DEFAULT | Py_TPFLAGS_BASETYPE,
     .slots = error_slots,
 };