bpo-26407: Do not mask errors in csv. (GH-20536)

Unexpected errors in calling the __iter__ method are no longer
masked by TypeError in csv.reader(), csv.writer.writerow() and
csv.writer.writerows().

1 files changed, 19 insertions, 1 deletions

diff --git a/Lib/test/test_csv.py b/Lib/test/test_csv.py
index a16d140..d421be0 100644
--- a/Lib/test/test_csv.py
+++ b/Lib/test/test_csv.py
@@ -14,6 +14,12 @@ from itertools import permutations
 from textwrap import dedent
 from collections import OrderedDict
 
+
+class BadIterable:
+    def __iter__(self):
+        raise OSError
+
+
 class Test_Csv(unittest.TestCase):
     """
     Test the underlying C csv parser in ways that are not appropriate
@@ -40,9 +46,15 @@ class Test_Csv(unittest.TestCase):
 
     def test_reader_arg_valid(self):
         self._test_arg_valid(csv.reader, [])
+        self.assertRaises(OSError, csv.reader, BadIterable())
 
     def test_writer_arg_valid(self):
         self._test_arg_valid(csv.writer, StringIO())
+        class BadWriter:
+            @property
+            def write(self):
+                raise OSError
+        self.assertRaises(OSError, csv.writer, BadWriter())
 
     def _test_default_attrs(self, ctor, *args):
         obj = ctor(*args)
@@ -141,6 +153,7 @@ class Test_Csv(unittest.TestCase):
         self._write_test([None], '""')
         self._write_error_test(csv.Error, [None], quoting = csv.QUOTE_NONE)
         # Check that exceptions are passed up the chain
+        self._write_error_test(OSError, BadIterable())
         class BadList:
             def __len__(self):
                 return 10;
@@ -230,6 +243,12 @@ class Test_Csv(unittest.TestCase):
             fileobj.seek(0)
             self.assertEqual(fileobj.read(), 'a\r\n""\r\n')
 
+    def test_writerows_errors(self):
+        with TemporaryFile("w+", newline='') as fileobj:
+            writer = csv.writer(fileobj)
+            self.assertRaises(TypeError, writer.writerows, None)
+            self.assertRaises(OSError, writer.writerows, BadIterable())
+
     @support.cpython_only
     def test_writerows_legacy_strings(self):
         import _testcapi
@@ -334,7 +353,6 @@ class Test_Csv(unittest.TestCase):
     def test_roundtrip_quoteed_newlines(self):
         with TemporaryFile("w+", newline='') as fileobj:
             writer = csv.writer(fileobj)
-            self.assertRaises(TypeError, writer.writerows, None)
             rows = [['a\nb','b'],['c','x\r\nd']]
             writer.writerows(rows)
             fileobj.seek(0)