fix(core): Ensure exit code 0 when no_args_is_help shows help

[Fabian665]

When no_args_is_help is True and no arguments are provided to a Typer application, the help message is displayed. However, an additional empty error panel also currently appears, and the application exits with status code 2. This issue affects applications using Click version 8.2.0 or later.

The root cause is a change in Click (pallets/click@d8763b93) where Command.parse_args now raises click.exceptions.NoArgsIsHelpError when no_args_is_help is true and no arguments are given. Previously, Click would print help and call ctx.exit() directly within parse_args.

Typer's generic except click.ClickException as e: block in core.py._main catches this NoArgsIsHelpError. The subsequent call to rich_utils.rich_format_error(e) (or e.show() if Rich is not used) results in the help message being displayed. This is because NoArgsIsHelpError is a subclass of click.UsageError, and UsageError.show() prints ctx.get_help(). However, this process also leads to an attempt to format a non-existent specific error message (as NoArgsIsHelpError.format_message() is empty), causing the blank error panel. Finally, sys.exit(e.exit_code) uses the UsageError's exit code of 2.

This commit addresses the issue by checking if the click.ClickException is of instance NoArgsIsHelpError and then raising click.exceptions.Exit(0)

This ensures that after the help message is displayed, the application exits cleanly with status code 0 and without displaying the erroneous empty error panel, aligning with the intended behavior of no_args_is_help.

[DHUKK]

Should we also update the test that was changed here tests/test_tutorial/test_commands/test_index/test_tutorial003.py - test_no_arg

to add back the

assert result.exit_code == 0

[Fabian665]

@DHUKK Thanks, I have restored the test.

I also added commented code for dropping Click<8.2 support.

[SeedyROM]

I'd love this to be merged, I think what's breaking the pipeline is that this issue is missing a label?

For now I'm just doing something akin to this!

First remove no_args_is_help from the options, then add this:

@app.callback(invoke_without_command=True)
def main(ctx: typer.Context):
    """My awesome CLI tool"""
    if ctx.invoked_subcommand is None:
        print(ctx.get_help())
        raise typer.Exit()

[Fabian665]

@SeedyROM It doesn't let me put a label, I guess only maintainers can do so.

[diablodale]

Rather than probing attrs and instance, I suggest using the exception we want to catch.
Click's init.py doesn't pull in the NoArgsIsHelpError exception into itself. So instead, we can easily do the same at the top of this file with;

from click.exceptions import NoArgsIsHelpError

and then here simply the code to be

...
except KeyboardInterrupt as e:
    raise click.exceptions.Exit(130) from e
except NoArgsIsHelpError as e:
    raise click.exceptions.Exit(0) from e
except click.ClickException as e:
...