Make --version write to stdout rather than stderr

Fix #8246

Author: nicoddemus

changelog/8246.breaking.rst

@@ -0,0 +1 @@
+``--version`` now writes version information to ``stdout`` rather than ``stderr``.

src/_pytest/helpconfig.py

@@ -127,17 +127,17 @@ def unset_tracing() -> None:
 
 def showversion(config: Config) -> None:
     if config.option.version > 1:
-        sys.stderr.write(
+        sys.stdout.write(
             "This is pytest version {}, imported from {}\n".format(
                 pytest.__version__, pytest.__file__
             )
         )
         plugininfo = getpluginversioninfo(config)
         if plugininfo:
             for line in plugininfo:
-                sys.stderr.write(line + "\n")
+                sys.stdout.write(line + "\n")
     else:
-        sys.stderr.write(f"pytest {pytest.__version__}\n")
+        sys.stdout.write(f"pytest {pytest.__version__}\n")
 
 
 def pytest_cmdline_main(config: Config) -> Optional[Union[int, ExitCode]]:

testing/test_config.py

@@ -1712,7 +1712,7 @@ def pytest_addoption(parser):
     assert result.ret == ExitCode.USAGE_ERROR
 
     result = pytester.runpytest("--version")
-    result.stderr.fnmatch_lines([f"pytest {pytest.__version__}"])
+    result.stdout.fnmatch_lines([f"pytest {pytest.__version__}"])
     assert result.ret == ExitCode.USAGE_ERROR
 
 

testing/test_helpconfig.py

@@ -7,16 +7,16 @@ def test_version_verbose(pytester: Pytester, pytestconfig, monkeypatch) -> None:
     monkeypatch.delenv("PYTEST_DISABLE_PLUGIN_AUTOLOAD")
     result = pytester.runpytest("--version", "--version")
     assert result.ret == 0
-    result.stderr.fnmatch_lines([f"*pytest*{pytest.__version__}*imported from*"])
+    result.stdout.fnmatch_lines([f"*pytest*{pytest.__version__}*imported from*"])
     if pytestconfig.pluginmanager.list_plugin_distinfo():
-        result.stderr.fnmatch_lines(["*setuptools registered plugins:", "*at*"])
+        result.stdout.fnmatch_lines(["*setuptools registered plugins:", "*at*"])
 
 
 def test_version_less_verbose(pytester: Pytester, pytestconfig, monkeypatch) -> None:
     monkeypatch.delenv("PYTEST_DISABLE_PLUGIN_AUTOLOAD")
     result = pytester.runpytest("--version")
     assert result.ret == 0
-    result.stderr.fnmatch_lines([f"pytest {pytest.__version__}"])
+    result.stdout.fnmatch_lines([f"pytest {pytest.__version__}"])
 
 
 def test_help(pytester: Pytester) -> None: