DEV: Allow streams to not be context managers

Many existing stdio capture and wrapper streams are only partial
implementations, most commonly missing `__enter__` and `__exit__`.
When StdioManager needs to integrate those streams into its service
it needs to suppress exceptions caused by those missing methods.

src/stdio_mgr/types.py

@@ -143,7 +143,8 @@ class _MultiCloseContextManager(StdioTuple):
     def __enter__(self):
         """Enter context of all members."""
         with ExitStack() as stack:
-            all(map(stack.enter_context, self))
+            # If not all items are TextIOBase, they may not have __exit__
+            self.suppress_all(AttributeError, stack.enter_context)
 
             self._close_files = stack.pop_all().close
 

tests/test_stdiomgr_base.py

@@ -41,6 +41,7 @@
 
 from stdio_mgr import stdio_mgr, StdioManager
 from stdio_mgr.stdio_mgr import _Tee
+from stdio_mgr.types import _MultiCloseContextManager, StdioTuple, TextIOTuple
 
 
 def test_context_manager_instance():
@@ -543,6 +544,24 @@ def test_tee_type():
     assert str(err.value) == "tee must be a TextIOBase."
 
 
+def test_non_closing_type():
+    """Test that incorrect type doesnt raise exceptions."""
+    # Ensure the type used has no __exit__ or close()
+    assert not hasattr("", "__exit__")
+    assert not hasattr("", "close")
+
+    with StdioTuple(("", "", "")):
+        pass
+
+    with _MultiCloseContextManager(("", "", "")):
+        pass
+
+    with pytest.raises(AssertionError) as err:
+        TextIOTuple(("", "", ""))
+
+    assert str(err.value) == "iterable must contain only TextIOBase"
+
+
 @pytest.mark.xfail(reason="Want to ensure 'real' warnings aren't suppressed")
 def test_bare_warning(skip_warnings):
     """Test that a "real" warning is exposed when raised."""