Keep caller-owned binary streams open after reading ASCII PLY

plyfile.py

@@ -155,6 +155,7 @@ def read(stream, mmap='c', known_list_len={}):
             indicates binary encoding.
         """
         (must_close, stream) = _open_stream(stream, 'read')
+        text_wrapper = None
         try:
             data = PlyData._parse_header(stream)
             if isinstance(stream.read(0), str):
@@ -165,13 +166,16 @@ def read(stream, mmap='c', known_list_len={}):
                                      "from text stream")
             else:
                 if data.text:
-                    data_stream = _io.TextIOWrapper(stream, 'ascii')
+                    text_wrapper = _io.TextIOWrapper(stream, 'ascii')
+                    data_stream = text_wrapper
                 else:
                     data_stream = stream
             for elt in data:
                 elt._read(data_stream, data.text, data.byte_order, mmap,
                           known_list_len=known_list_len.get(elt.name, {}))
         finally:
+            if text_wrapper is not None:
+                text_wrapper.detach()
             if must_close:
                 stream.close()
 

test/test_stream_ownership.py

@@ -0,0 +1,22 @@
+from io import BytesIO
+
+import pytest
+
+from plyfile import PlyData, PlyElementParseError
+
+
+@pytest.mark.parametrize('valid', [True, False])
+def test_read_ascii_leaves_caller_binary_stream_open(valid):
+    payload = (b'ply\nformat ascii 1.0\nelement vertex 1\n'
+               b'property float x\nend_header\n')
+    payload += b'1\n' if valid else b'invalid\n'
+    stream = BytesIO(payload)
+    if valid:
+        data = PlyData.read(stream)
+        assert data['vertex']['x'][0] == 1
+    else:
+        with pytest.raises(PlyElementParseError):
+            PlyData.read(stream)
+    assert not stream.closed
+    stream.seek(0)
+    assert stream.read() == payload