Fixed csv dialect bug with sniffing (#215)

* Fixed csv dialect bug

* Fixed linting

tabulator/parsers/csv.py

@@ -119,7 +119,8 @@ def __prepare_dialect(self, stream):
             if not dialect.escapechar:
                 dialect.doublequote = True
         except csv.Error:
-            dialect = csv.excel
+            class dialect(csv.excel):
+                pass
         for key, value in self.__options.items():
             setattr(dialect, key, value)
 

tests/formats/test_csv.py

@@ -5,6 +5,7 @@
 from __future__ import unicode_literals
 
 import io
+import pytest
 from mock import Mock
 from tabulator import Stream
 from tabulator.parsers.csv import CSVParser
@@ -137,6 +138,15 @@ def test_stream_csv_detect_delimiter_pipe():
         assert stream.read() == [['a1', 'b1'], ['a2', 'b2']]
 
 
+def test_stream_csv_dialect_should_not_persist_if_sniffing_fails_issue_goodtables_228():
+    source1 = 'a;b;c\n#comment'
+    source2 = 'a,b,c\n#comment'
+    with Stream(source1, scheme='text', format='csv', headers=1, delimiter=';') as stream:
+        assert stream.headers == ['a', 'b', 'c']
+    with Stream(source2, scheme='text', format='csv', headers=1) as stream:
+        assert stream.headers == ['a', 'b', 'c']
+
+
 # Parser
 
 def test_parser_csv():