Any string from environment variable casts to True, even "false"

[MartinBernstorff]

First Check

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Example Code

MRE repo: https://github.com/MartinBernstorff/typer-false-envvar-repro

Description

I would expect an envvar with value "false" to be resolved to False.

Operating System

macOS

Operating System Details

No response

Typer Version

0.16.0

Python Version

Tested with 3.13, 3.12, 3.11

Additional Context

Thanks a ton for the work you guys do! Love Typer; hope this MRE is easy to follow.

[david-polak-ataccama]

Can confirm with 0.16.0 envvar handling is broken.

• Setup test

cat << 'EOF' > typer_test.py
#!/usr/bin/env python3
import typer

app = typer.Typer()

@app.command()
def main(
    verbose: bool = typer.Option(
        False,
        "--verbose", "-v",
        envvar="VERBOSE",
        help="Enable verbose mode via flag or VERBOSE env var",
    )
):
    typer.echo(f"verbose={verbose!r}")

if __name__ == "__main__":
    app()
EOF

chmod +x typer_test.py

• Venv

python -m venv .venv && source .venv/bin/activate

• Install

pip install typer==0.15.4 --force-reinstall --no-cache-dir
pip install typer==0.16.0 --force-reinstall --no-cache-dir

• Run and verify

VERBOSE="False" python typer_test.py
VERBOSE="True" python typer_test.py

Full output screenshot

[Sigeth]

Can confirm it happens to me too with 0.16.0

Just a link to the Click documentation : Options - Click Documentation

Note that setting the envvar without any value works and sets verbose to False. The wrong behavior only happens when trying to set envvar to a value that should deactivate the flag as stated in the documentation : false, 0, no, off, f, n

[svlandeg]

Thanks for the report!

Are you using Click 8.2.0 or higher? Do you see the same behaviour if you would downgrade to click<8.2 (while staying on Typer 0.16.0)?

[Sigeth]

I can confirm the problem occurs with Click 8.2.1, but not with Click 8.1.8 while staying with typer 0.16

[svlandeg]

Thanks! That helps to narrow down the search 🕵️

[svlandeg]

While I can confirm the bug, it also happens with pure Click code, and it was thoroughly investigated there. It's likely that the next Click release (probably 8.3.0) will fix this.