Issue #12591: Allow io.TextIOWrapper to work with raw IO objects (without

a read1() method), and add a *write_through* parameter to
mandate unbuffered writes.

1 files changed, 21 insertions, 0 deletions

diff --git a/Lib/test/test_io.py b/Lib/test/test_io.py
index 419921f..0d68ca1 100644
--- a/Lib/test/test_io.py
+++ b/Lib/test/test_io.py
@@ -2314,6 +2314,27 @@ class TextIOWrapperTest(unittest.TestCase):
         with self.assertRaises(AttributeError):
             txt.buffer = buf
 
+    def test_rawio(self):
+        # Issue #12591: TextIOWrapper must work with raw I/O objects, so
+        # that subprocess.Popen() can have the required unbuffered
+        # semantics with universal_newlines=True.
+        raw = self.MockRawIO([b'abc', b'def', b'ghi\njkl\nopq\n'])
+        txt = self.TextIOWrapper(raw, encoding='ascii', newline='\n')
+        # Reads
+        self.assertEqual(txt.read(4), 'abcd')
+        self.assertEqual(txt.readline(), 'efghi\n')
+        self.assertEqual(list(txt), ['jkl\n', 'opq\n'])
+
+    def test_rawio_write_through(self):
+        # Issue #12591: with write_through=True, writes don't need a flush
+        raw = self.MockRawIO([b'abc', b'def', b'ghi\njkl\nopq\n'])
+        txt = self.TextIOWrapper(raw, encoding='ascii', newline='\n',
+                                 write_through=True)
+        txt.write('1')
+        txt.write('23\n4')
+        txt.write('5')
+        self.assertEqual(b''.join(raw._write_stack), b'123\n45')
+
 class CTextIOWrapperTest(TextIOWrapperTest):
 
     def test_initialization(self):