fix #6951: allow to write TerminalReporter.writer

changelog/6951.bugfix.rst

@@ -0,0 +1 @@
+Allow users to still set the deprecated ``TerminalReporter.writer`` attribute.

src/_pytest/deprecated.py

@@ -55,3 +55,9 @@
     "The pytest_collect_directory hook is not working.\n"
     "Please use collect_ignore in conftests or pytest_collection_modifyitems."
 )
+
+
+TERMINALWRITER_WRITER = PytestDeprecationWarning(
+    "The TerminalReporter.writer attribute is deprecated, use TerminalReporter._tw instead at your own risk.\n"
+    "See https://docs.pytest.org/en/latest/deprecations.html#terminalreporter-writer for more information."
+)

src/_pytest/terminal.py

@@ -29,6 +29,7 @@
 from _pytest._io import TerminalWriter
 from _pytest.config import Config
 from _pytest.config import ExitCode
+from _pytest.deprecated import TERMINALWRITER_WRITER
 from _pytest.main import Session
 from _pytest.reports import CollectReport
 from _pytest.reports import TestReport
@@ -284,14 +285,14 @@ def __init__(self, config: Config, file=None) -> None:
 
     @property
     def writer(self) -> TerminalWriter:
-        warnings.warn(
-            pytest.PytestDeprecationWarning(
-                "TerminalReporter.writer attribute is deprecated, use TerminalReporter._tw instead at your own risk.\n"
-                "See https://docs.pytest.org/en/latest/deprecations.html#terminalreporter-writer for more information."
-            )
-        )
+        warnings.warn(TERMINALWRITER_WRITER, stacklevel=2)
         return self._tw
 
+    @writer.setter
+    def writer(self, value: TerminalWriter):
+        warnings.warn(TERMINALWRITER_WRITER, stacklevel=2)
+        self._tw = value
+
     def _determine_show_progress_info(self):
         """Return True if we should display progress information based on the current config"""
         # do not show progress if we are not capturing output (#3038)

testing/deprecated_test.py

@@ -36,8 +36,15 @@ def test_terminal_reporter_writer_attr(pytestconfig):
     except ImportError:
         pass
     terminal_reporter = pytestconfig.pluginmanager.get_plugin("terminalreporter")
+    expected_tw = terminal_reporter._tw
+
+    with pytest.warns(pytest.PytestDeprecationWarning):
+        assert terminal_reporter.writer is expected_tw
+
     with pytest.warns(pytest.PytestDeprecationWarning):
-        assert terminal_reporter.writer is terminal_reporter._tw
+        terminal_reporter.writer = expected_tw
+
+    assert terminal_reporter._tw is expected_tw
 
 
 @pytest.mark.parametrize("plugin", sorted(deprecated.DEPRECATED_EXTERNAL_PLUGINS))