Added unit tests for when to redirect/capture sys.stdout.

Author: kmvanbrunt

CHANGELOG.md

@@ -15,6 +15,10 @@
     - Added `Cmd.macro_arg_complete()` which tab completes arguments to a macro. Its default
       behavior is to perform path completion, but it can be overridden as needed.
 
+    - Bug Fixes
+        - No longer redirecting `sys.stdout` if it's a different stream than `self.stdout`. This
+          fixes issue where we overwrote an application's `sys.stdout` while redirecting.
+
 ## 2.7.0 (June 30, 2025)
 
 - Enhancements

cmd2/py_bridge.py

@@ -110,6 +110,7 @@ def __call__(self, command: str, *, echo: Optional[bool] = None) -> CommandResul
         if echo is None:
             echo = self.cmd_echo
 
+        # Only capture sys.stdout if it's the same stream as self.stdout
         stdouts_match = self._cmd2_app.stdout == sys.stdout
 
         # This will be used to capture _cmd2_app.stdout and sys.stdout

tests/conftest.py

@@ -2,10 +2,7 @@
 
 import argparse
 import sys
-from contextlib import (
-    redirect_stderr,
-    redirect_stdout,
-)
+from contextlib import redirect_stderr
 from typing import (
     Optional,
     Union,
@@ -116,8 +113,9 @@ def normalize(block):
 
 def run_cmd(app, cmd):
     """Clear out and err StdSim buffers, run the command, and return out and err"""
-    saved_sysout = sys.stdout
-    sys.stdout = app.stdout
+
+    # Only capture sys.stdout if it's the same stream as self.stdout
+    stdouts_match = app.stdout == sys.stdout
 
     # This will be used to capture app.stdout and sys.stdout
     copy_cmd_stdout = StdSim(app.stdout)
@@ -127,11 +125,14 @@ def run_cmd(app, cmd):
 
     try:
         app.stdout = copy_cmd_stdout
-        with redirect_stdout(copy_cmd_stdout), redirect_stderr(copy_stderr):
+        if stdouts_match:
+            sys.stdout = app.stdout
+        with redirect_stderr(copy_stderr):
             app.onecmd_plus_hooks(cmd)
     finally:
         app.stdout = copy_cmd_stdout.inner_stream
-        sys.stdout = saved_sysout
+        if stdouts_match:
+            sys.stdout = app.stdout
 
     out = copy_cmd_stdout.getvalue()
     err = copy_stderr.getvalue()

tests/pyscript/stdout_capture.py

@@ -1,25 +1,4 @@
-# This script demonstrates when output of a command finalization hook is captured by a pyscript app() call
-import sys
-
-# The unit test framework passes in the string being printed by the command finalization hook
-hook_output = sys.argv[1]
-
-# Run a help command which results in 1 call to onecmd_plus_hooks
-res = app('help')
-
-# hook_output will not be captured because there are no nested calls to onecmd_plus_hooks
-if hook_output not in res.stdout:
-    print("PASSED")
-else:
-    print("FAILED")
-
-# Run the last command in the history
-res = app('history -r -1')
-
-# All output of the history command will be captured. This includes all output of the commands
-# started in do_history() using onecmd_plus_hooks(), including any output in those commands' hooks.
-# Therefore we expect the hook_output to show up this time.
-if hook_output in res.stdout:
-    print("PASSED")
-else:
-    print("FAILED")
+# This script demonstrates that cmd2 can capture sys.stdout and self.stdout when both point to the same stream.
+# Set base_app.self_in_py to True before running this script.
+print("print")
+self.poutput("poutput")

tests/test_argparse_completer.py

@@ -15,10 +15,7 @@
     argparse_custom,
     with_argparser,
 )
-from cmd2.utils import (
-    StdSim,
-    align_right,
-)
+from cmd2.utils import align_right
 
 from .conftest import (
     complete_tester,
@@ -334,9 +331,7 @@ def do_standalone(self, args: argparse.Namespace) -> None:
 
 @pytest.fixture
 def ac_app():
-    app = ArgparseCompleterTester()
-    app.stdout = StdSim(app.stdout)
-    return app
+    return ArgparseCompleterTester()
 
 
 @pytest.mark.parametrize('command', ['music', 'music create', 'music create rock', 'music create jazz'])