ALL-PARA0002 · configuration_object_parameter

Count parameters a callable only reads attributes from.

This is a deterministic rule for all languages. Read its implementation.

Definition

Report a configuration parameter whose every resolved use is an attribute read, and which is read for at least minimum_reads distinct names. A configuration type is identified by the configurable, case-insensitive markers in its annotation. Such a parameter does not need the object, only those values. Taking the whole object hides which parts the callable depends on, forces every caller and every test to build a complete object, and couples the callable to a type it never uses as a type.

Evidence

Each finding names the callable, the parameter, its declared type, and every attribute name the body reads from it, since those names are the narrower contract the callable actually wants. The repair is a choice, because a settings object a framework hands over is not one a caller can unpack. The value is the number of such parameters.

Exceptions

A value object such as a source span is not configuration and is skipped even when a renderer reads several of its fields. A parameter with any use other than an attribute read is skipped, because the callable then depends on the object itself. A parameter whose uses could not all be resolved is skipped rather than guessed. A project can replace configuration_markers, raise minimum_reads, or disable the rule where a framework deliberately supplies settings.

Examples

A function that reads only config.host and config.port returns 1 and should take those two values. A function reading span.path and span.start_line returns 0, as does one that reads config.host and also passes config onward.

References

• Cites “Refactoring”, replace parameter with explicit methods
• Cites “Clean Code”, function arguments
• Cites “Implementation Patterns”, on revealing intent in signatures