"ValueError: I/O operation on closed file" if pytest live logging with clirunner

[hamstero]

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Example Code

# test_hello.py
from typer.testing import CliRunner
from hello import app

runner = CliRunner()

def test_hello() -> None:
    _ = runner.invoke(app, ["hello"])


# hello.py
import logging
import typer

logger = logging.getLogger(__name__)
app = typer.Typer()

@app.command()
def hello() -> None:
    """Simple program that greets NAME for a total of COUNT times."""
    logger.warning("Greeting user now...")
    typer.echo(f"Hello, world!")

@app.command()
def bye(name: str = "world") -> None:
    """Another command to avoid empty CLI issues."""
    typer.echo(f"Goodbye, {name}!")

if __name__ == "__main__":
    app()

# cli
pytest --log-cli-level=INFO test_hello.py

# Notice "ValueError: I/O operation on closed file."

Description

I can get the example to work as reported in pallets/click#824 (comment) with click 8.1.8.

But I want it working with Typer too, and unfortunately that still fails. Tried with

uv tree
Resolved 14 packages in 10ms
logs v0.1.0
├── click v8.1.8
├── typer v0.17.3
│ ├── click v8.1.8
│ ├── rich v14.1.0
│ │ ├── markdown-it-py v4.0.0
│ │ │ └── mdurl v0.1.2
│ │ └── pygments v2.19.2
│ ├── shellingham v1.5.4
│ └── typing-extensions v4.15.0
└── pytest v8.4.1 (group: dev)
├── iniconfig v2.1.0
├── packaging v25.0
├── pluggy v1.6.0
└── pygments v2.19.2

and also latest typer 0.17.3 and latest click 8.2.1.

Anyone know of a solution to get live logging working with pytest and clirunner with Typer? The exampel below fails.

# test_hello.py
from typer.testing import CliRunner
from hello import app

runner = CliRunner()

def test_hello() -> None:
    _ = runner.invoke(app, ["hello"])

# hello.py
import logging
import typer

logger = logging.getLogger(__name__)
app = typer.Typer()

@app.command()
def hello() -> None:
    """Simple program that greets NAME for a total of COUNT times."""
    logger.warning("Greeting user now...")
    typer.echo(f"Hello, world!")

@app.command()
def bye(name: str = "world") -> None:
    """Another command to avoid empty CLI issues."""
    typer.echo(f"Goodbye, {name}!")

if __name__ == "__main__":
    app()

pytest --log-cli-level=INFO test_hello.py

results in

...
            finally:
                sys.stdout.flush()
>               stdout = outstreams[0].getvalue()
                         ^^^^^^^^^^^^^^^^^^^^^^^^
E               ValueError: I/O operation on closed file

It's important to enable live pytest logging (like via --log-cli-level). That's when the error occurs (and you actually do any logging).

Operating System

Windows, macOS

Operating System Details

No response

Typer Version

0.17.3

Python Version

3.13.7

Additional Context

No response