Flag option with secondary opts: show_default=True does not show value from default_map in "help" output

[a-stangl]

I'm setting the default_map from a config file, and it seems the values from the default_map are not correctly shown in the --help output if I set show_default=True on my option.

My Option looks like this:

@click.option(
    "--long/--short",
    "-l/-s",
    is_flag=True,
    show_default=True,
    help="show additional information like size and creation date",
)

I initialize the default_map with a custom command class that I attach via the @click.command decorator like this @click.command(cls=ConfigAwareCommand)

from click import Command as _Command


class ConfigAwareCommand(_Command):
    def __init__(self, *args, **kwargs):
        kwargs["context_settings"] = {
            "default_map": CONFIG.get_cli_command_defaults(kwargs["name"])
        }
        super().__init__(*args, **kwargs)

The default_map value is in my example {'long': True}. In the --help output, the default value is shown like this

  -l, --long / -s, --short        show additional information like size and
                                  creation date  [default: short]

When executing the command, the default value from the default_map is used correctly (long defaults to True).

During debugging, I might have found the culprit inside src/click/core.py

            elif self.is_bool_flag and self.secondary_opts:
                # For boolean flags that have distinct True/False opts,
                # use the opt without prefix instead of the value.
                default_string = _split_opt(
                    (self.opts if self.default else self.secondary_opts)[0]
                )[1]

As you can see, self.default is used instead of the default_value variable that is initialized further above this code snippet.

If I change the part of the code above and use default_value instead of self.default the help output shows the correct default values from the default_map.

            elif self.is_bool_flag and self.secondary_opts:
                # For boolean flags that have distinct True/False opts,
                # use the opt without prefix instead of the value.
                default_string = _split_opt(
                    (self.opts if default_value else self.secondary_opts)[0]
                )[1]

I am not sure if I do something wrong or if this is indeed a bug.

Environment:

• Python version: 3.10.12
• Click version: 8.1.7