IMPALA-11332: Fix trailing whitespace for CSV output

The current CSV output is stripping trailing
whitespaces from the last line of CSV output. This
rstrip() was intended to remove an extra newline,
but it is matching other white space. This is a
problem for a SQL query like:
select 'Trailing whitespace          ';

This changes the rstrip() to rstrip('\n') to
avoid removing the other white space.

Testing:
 - Current shell tests pass
 - Added a shell test that verifies trailing whitespace
   is not being stripped.

Change-Id: I69d032ca2f581587b0938d0878fdf402fee0d57e
Reviewed-on: http://gerrit.cloudera.org:8080/18580
Reviewed-by: Quanlong Huang <huangquanlong@gmail.com>
Tested-by: Impala Public Jenkins <impala-public-jenkins@cloudera.com>

shell/shell_output.py

@@ -90,7 +90,14 @@ def format(self, rows):
         row = [val.encode('utf-8', 'replace') if isinstance(val, unicode) else val
             for val in row]
       writer.writerow(row)
-    rows = temp_buffer.getvalue().rstrip()
+    # The CSV writer produces an extra newline. Strip that extra newline (and
+    # only that extra newline). csv wraps newlines for data values in quotes,
+    # so rstrip will be limited to the extra newline.
+    if sys.version_info.major == 2:
+      # Python 2 is in encoded Unicode bytes, so this needs to be a bytes \n.
+      rows = temp_buffer.getvalue().rstrip(b'\n')
+    else:
+      rows = temp_buffer.getvalue().rstrip('\n')
     temp_buffer.close()
     return rows
 

tests/shell/test_shell_commandline.py

@@ -1254,3 +1254,13 @@ def test_http_socket_timeout(self, vector):
     result = run_impala_shell_cmd(vector, args + ['--http_socket_timeout_s=None'])
     assert result.stderr == ""
     assert result.stdout == "0\n"
+
+  def test_trailing_whitespace(self, vector):
+    """Test CSV output with trailing whitespace"""
+
+    # Ten trailing spaces
+    query = "select 'Trailing Whitespace          '"
+    # Only one column, no need for output_delimiter
+    output = run_impala_shell_cmd(vector, ['-q', query, '-B'])
+    assert "Fetched 1 row(s)" in output.stderr
+    assert "Trailing Whitespace          \n" in output.stdout