How it works

This works by mutating the default values in the underlying click context (click.Context.default_map) before the command is executed (see phha/click_config_file). It is essentially overwriting the default values that you specified in your source code. Then, the shell environment variables and CLI parameters are parsed by typer to override the values already set.

Note: You must use is_eager=True in the parameter definition because that will cause it to be processed first. If you don't use is_eager, then your parameter values will depend on the order in which they were processed (read: unpredictably).