NamedTextIOWrapper: stop closing buffer

The NamedTextIOWrapper is closing the buffers
that are owned by the StreamMixer, so
implement a close() method that prevents
it from doing that.

Refs #824
Refs #2993

Author: pjonsson

src/click/testing.py

@@ -98,18 +98,6 @@ def __init__(self) -> None:
         self.stdout: io.BytesIO = BytesIOCopy(copy_to=self.output)
         self.stderr: io.BytesIO = BytesIOCopy(copy_to=self.output)
 
-    def __del__(self) -> None:
-        """
-        Guarantee that embedded file-like objects are closed in a
-        predictable order, protecting against races between
-        self.output being closed and other streams being flushed on close
-
-        .. versionadded:: 8.2.2
-        """
-        self.stderr.close()
-        self.stdout.close()
-        self.output.close()
-
 
 class _NamedTextIOWrapper(io.TextIOWrapper):
     def __init__(
@@ -119,6 +107,15 @@ def __init__(
         self._name = name
         self._mode = mode
 
+    def close(self) -> None:
+        """
+        The buffer this object contains belongs to some other object, so
+        prevent the default __del__ implementation from closing that buffer.
+
+        .. versionadded:: 8.3.2
+        """
+        ...
+
     @property
     def name(self) -> str:
         return self._name

tests/test_testing_logging.py

@@ -0,0 +1,26 @@
+import logging
+
+import click
+from click.testing import CliRunner
+
+
+# Minimized version of:
+# https://github.com/pallets/click/issues/824#issuecomment-3027263262
+#
+# Test needs to be run as "pytest --log-cli-level 30 tests/test_testing_logging.py"
+# to test the intended functionality.
+def test_runner_logger():
+    logger = logging.getLogger(__name__)
+
+    @click.command()
+    @click.option("--name", prompt="Your name", help="The person to greet.")
+    def hello(name):
+        logger.warning("Greeting user now...")
+        click.echo(f"Hello, {name}!")
+
+    runner = CliRunner()
+    result = runner.invoke(hello, input="Peter")
+    assert result.exit_code == 0
+    # FIXME: second half of the output is missing.
+    assert result.output == "Your name: Peter\n"
+    # assert result.output == "Your name: Peter\nHello, Peter!\n"