typer not respecting sys.stdout.isatty mock

[lilibutt]

First Check

• I added a very descriptive title here.
• I used the GitHub search to find a similar question and didn't find it.
• I searched the Typer documentation, with the integrated search.
• I already searched in Google "How to X in Typer" and didn't find any information.
• I already read and followed all the tutorial in the docs and didn't find an answer.
• I already checked if it is not related to Typer but to Click.

Commit to Help

• I commit to help with one of those options 👆

Example Code

# main.py
import sys

import typer

app = typer.Typer()

@app.command()
def main(
    interactive: bool = typer.Option(
        sys.stdout.isatty(),
        "--interactive",
    ),
) -> None:
    print(f"interactive={interactive} sys.stdout.isatty()={sys.stdout.isatty()}")


if __name__ == "__main__":
    app()

# test_main.py
import sys

from unittest import mock

from typer.testing import CliRunner

from main import app

runner = CliRunner()

def test_force_no_tty(): -> None
    with mock.patch("sys.stdout.isatty", return_value=False):
        result = runner.invoke(app)
        assert not sys.stdout.isatty()
        assert "interactive=False sys.stdout.isatty()=False" in result.stdout


def test_force_tty(): -> None
    with mock.patch("sys.stdout.isatty", return_value=True):
        result = runner.invoke(app)
        assert sys.stdout.isatty()
        assert "interactive=True sys.stdout.isatty()=True" in result.stdout

Description

The above main.py prints the absence of a tty when run without one

❯ ./main.py </dev/null |& cat
interactive=False sys.stdout.isatty()=False

The second test in test_main.py fails. this is a typer issue as assert sys.stdout.isatty() passes but doesn't return True in the application

    def test_force_tty():
        with mock.patch("sys.stdout.isatty", return_value=True):
            result = runner.invoke(app)
            assert sys.stdout.isatty()
>           assert "interactive=True sys.stdout.isatty()=True" in result.stdout
E           AssertionError: assert 'interactive=True sys.stdout.isatty()=True' in 'interactive=False sys.stdout.isatty()=False\n'
E            +  where 'interactive=False sys.stdout.isatty()=False\n' = <Result okay>.stdout

Operating System

Linux, macOS

Operating System Details

❯ uname -a
Darwin mbp 23.1.0 Darwin Kernel Version 23.1.0: Mon Oct  9 21:28:45 PDT 2023; root:xnu-10002.41.9~6/RELEASE_ARM64_T6020 arm64

same issue on Linux w/ Python 3.11

Typer Version

0.9.0

Python Version

Python 3.7.12

Additional Context

No response

[lilibutt]

appears this might be a Click thing :-/

#! /usr/bin/env python

import sys

import click

@click.command()
@click.option("--interactive", default=sys.stdout.isatty())
def main(interactive):
    print(interactive)

if __name__ == '__main__':
    main()

test_main.py

import sys

from click.testing import CliRunner
from main import main

from unittest import mock

runner = CliRunner()

def test_interactive():
  with mock.patch("sys.stdout.isatty", return_value=True):
    assert sys.stdout.isatty()
    result = runner.invoke(main)
    assert result.output == 'True\n'

❯ pytest test_main.py
========================================================= test session starts ==========================================================
platform darwin -- Python 3.7.12, pytest-7.4.3, pluggy-1.2.0
rootdir: /Users/tdoherty/test
collected 1 item

test_main.py F                                                                                                                   [100%]

=============================================================== FAILURES ===============================================================
___________________________________________________________ test_interactive ___________________________________________________________

    def test_interactive():
      with mock.patch("sys.stdout.isatty", return_value=True):
        assert sys.stdout.isatty()
        result = runner.invoke(main)
>       assert result.output == 'True\n'
E       AssertionError: assert 'False\n' == 'True\n'
E         - True
E         + False

test_main.py:14: AssertionError
======================================================= short test summary info ========================================================
FAILED test_main.py::test_interactive - AssertionError: assert 'False\n' == 'True\n'
========================================================== 1 failed in 0.03s ===========================================================

[The-Compiler]

Your original example results in a SyntaxError, and then results in both tests failing:

• test_force_no_tty due to interactive=True sys.stdout.isatty()=False
• test_force_tty due to interactive=True sys.stdout.isatty()=False

Can you show the code you're actually running? Because evidently you're not running the code you posted.

---

As for your Click example, this is what I'd expect to happen, and it's not related to either Python nor Click. Decorators are run by Python when your module is imported, thus @click.option("--interactive", default=sys.stdout.isatty()) turns to @click.option("--interactive", default=True) at import time, and thus both Click and Typer (or anything else!) will only ever see True there.