fix #1245 (#1246)

* expose parallel show output not working

* fix #1245

docs/changelog/1245.bugfix.rst

@@ -0,0 +1 @@
+:conf:`parallel_show_output` does not work with tox 3.8

src/tox/session/commands/run/parallel.py

@@ -26,6 +26,7 @@ def run_parallel(config, venv_dict):
     finished = Event()
 
     show_progress = not live_out and reporter.verbosity() > reporter.Verbosity.QUIET
+
     with Spinner(enabled=show_progress) as spinner:
 
         def run_in_thread(tox_env, os_env, processes):
@@ -42,13 +43,17 @@ def run_in_thread(tox_env, os_env, processes):
                     def collect_process(process):
                         processes[tox_env] = (action, process)
 
-                    action.popen(
+                    print_out = not live_out and tox_env.envconfig.parallel_show_output
+                    output = action.popen(
                         args=args_sub,
                         env=os_env,
                         redirect=not live_out,
                         capture_err=live_out,
                         callback=collect_process,
+                        returnout=print_out,
                     )
+                    if print_out:
+                        reporter.verbosity0(output)
 
             except InvocationError as err:
                 status = "parallel child exit code {}".format(err.exit_code)

tests/unit/session/test_parallel.py

@@ -158,3 +158,30 @@ def test_parallel_recreate(cmd, initproj, monkeypatch):
     end = log_dir.listdir()
     assert len(end) >= 3
     assert not ({f.basename for f in after} - {f.basename for f in end})
+
+
+def test_parallel_show_output(cmd, initproj, monkeypatch):
+    monkeypatch.setenv(str("_TOX_SKIP_ENV_CREATION_TEST"), str("1"))
+    tox_ini = """\
+[tox]
+envlist = e1,e2,e3
+skipsdist = true
+
+[testenv]
+whitelist_externals = {}
+commands =
+    python -c 'import sys; sys.stderr.write("stderr env"); sys.stdout.write("stdout env")'
+
+[testenv:e3]
+commands =
+    python -c 'import sys; sys.stderr.write("stderr always "); sys.stdout.write("stdout always ")'
+parallel_show_output = True
+""".format(
+        sys.executable
+    )
+    initproj("pkg123-0.7", filedefs={"tox.ini": tox_ini})
+    result = cmd("-p", "all")
+    result.assert_success()
+    assert "stdout env" not in result.out, result.output()
+    assert "stderr env" not in result.out, result.output()
+    assert "stdout always stderr always" in result.out, result.output()