bpo-20028: Improve error message of csv.Dialect when initializing (GH-28705)

(cherry picked from commit 34bbc87b2ddbaf245fbed6443c3e620f80c6a843)

Co-authored-by: Dong-hee Na <donghee.na@python.org>

1 files changed, 30 insertions, 1 deletions

diff --git a/Lib/test/test_csv.py b/Lib/test/test_csv.py
index 09e72a71f1..6e5dfc63d4 100644
--- a/Lib/test/test_csv.py
+++ b/Lib/test/test_csv.py
@@ -897,7 +897,7 @@ class TestDialectValidity(unittest.TestCase):
         with self.assertRaises(csv.Error) as cm:
             mydialect()
         self.assertEqual(str(cm.exception),
-                         '"quotechar" must be string, not int')
+                         '"quotechar" must be string or None, not int')
 
     def test_delimiter(self):
         class mydialect(csv.Dialect):
@@ -934,6 +934,35 @@ class TestDialectValidity(unittest.TestCase):
         self.assertEqual(str(cm.exception),
                          '"delimiter" must be string, not int')
 
+        mydialect.delimiter = None
+        with self.assertRaises(csv.Error) as cm:
+            mydialect()
+        self.assertEqual(str(cm.exception),
+                         '"delimiter" must be string, not NoneType')
+
+    def test_escapechar(self):
+        class mydialect(csv.Dialect):
+            delimiter = ";"
+            escapechar = '\\'
+            doublequote = False
+            skipinitialspace = True
+            lineterminator = '\r\n'
+            quoting = csv.QUOTE_NONE
+        d = mydialect()
+        self.assertEqual(d.escapechar, "\\")
+
+        mydialect.escapechar = "**"
+        with self.assertRaisesRegex(csv.Error, '"escapechar" must be a 1-character string'):
+            mydialect()
+
+        mydialect.escapechar = b"*"
+        with self.assertRaisesRegex(csv.Error, '"escapechar" must be string or None, not bytes'):
+            mydialect()
+
+        mydialect.escapechar = 4
+        with self.assertRaisesRegex(csv.Error, '"escapechar" must be string or None, not int'):
+            mydialect()
+
     def test_lineterminator(self):
         class mydialect(csv.Dialect):
             delimiter = ";"