A common configuration-storage class with a .diag() method

Description

This module provides four classes that may be used as base classes for storing program runtime configuration with a verbose boolean field. The classes provide a .diag(func) method that will check the object's verbose field and, if it is set to a true value, invoke the specified function and output the message that it returns. If the message is not expensive to format (e.g. it does not include stringifying elaborate data structures), the .diag_(msg) method may be used instead.

The ConfigUnfrozen and ConfigUnfrozenStdOut classes are normal dataclasses, while the Config and ConfigStdOut ones are frozen.

The Config and ConfigUnfrozen classes will output any diagnostic messages to the standard error stream, while the ConfigStdOut and ConfigUnfrozenStdOut ones will output the diagnostic messages to the standard output stream.

For compatibility with cfg-diag versions 0.1.x and 0.2.x, there is also a parallel ConfigDiag* class hierarchy; the classes there are organized in exactly the same way as those in the Config* hierarchy, but they only provide a single .diag(msg) method that accepts a fixed, already-built, string instead of a callback function. These classes are deprecated and will most probably be removed in a future version of the cfg-diag library.

Example

Subclass the frozen Config class, add a program-specific field:

@dataclasses.dataclass(frozen=True)
class Config(cfg_diag.Config):
    """Runtime configuration for the fribble program."""
    path: pathlib.Path

Initialize this class from an argument parser object:

return Config(path=args.path, verbose=args.verbose)

Output a diagnostic message if requested:

cfg.diag_("This will either appear or it will not")
cfg.diag(lambda: f"Here's the thing: {thing!r}")

Contact

This module is developed in a GitHub repository. Contact the StorPool support team for information.